Prof. dr hab. Adam Miranowicz

Prof. dr hab. Adam Miranowicz

Department of Nonlinear Optics

Tel: +48 61 829 5283
Loc: wing G, second floor, room 280
Email: miran@amu.edu.pl
URL: https://miran.web.amu.edu.pl/

Scientific degrees

Title of professor – 2014
Habilitation – 2005
PhD in physics – 1994

Research interests

Keywords: theoretical nonlinear and quantum optics, quantum computation and information, quantum cryptography, nanoscience, atom optics

Quantum state engineering with light and atoms: Generation and manipulation of the states of light interacting with natural and artificial atoms, including quantum dots, superconducting qubits in optical, superconducting and nanomechanical resonators. Quantum state and process tomography. Photon and phonon blockades (optical-state truncation methods). Conditional photon-count measurements.
Nanoscience: Entangled networks of quantum dots in microcavities. Quantum operations (including quantum gates and tomography) of semiconductor quantum wells using NMR methods. Quantum limits of nanomechanical resonators. Hybrid nanosystems.
Quantum information processing and quantum cryptography: Solid-state implementations of quantum computers and cryptosystems based on quantum dots and cavity QED. Teleportation protocols.
Nonclassical light: Generation of quantum light with the reduced quantum noise (sub-Poissonian, antibunched and squeezed light). Generation of quantum superpositions of macroscopically distinct states (Schrödinger cats and kittens). Interaction of quantum-optical fields with nonlinear media. Photon statistics.
Quantum entanglement and nonlocality: Criteria, measures, and paradoxes of quantum entanglement and Bell nonlocality for two-qubit systems. Spatial and temporal quantum steering.
Phase problem, coherence, and decoherence: Quantum phase properties of nonlinear optical phenomena within various approaches, including the Pegg-Barnett, Garrison-Wong and phase-space formalisms. Coherence control. Systems preserving or enhancing coherence.
Quantum mechanics in finite dimensions: Generalized harmonic-oscillator states in finite-dimensional Hilbert spaces. Analysis of their properties and possibilities of generation.
Quantum vs classical descriptions of nonclassical phenomena: General criteria and measures of nonclassical fields: Glauber-Sudarshan quasidistribution; nonclassical depth, volume, and distance; a unified description of nonclassicality and entanglement. Classical trajectories.
Raman scattering: Theoretical approach to quantum-statistical theories of Raman scattering processes within standing-wave models.ods

Memberships in editorial boards

Editorial Board of Frontiers
Editorial Board of International Journal of Optics
Editorial Board of Advances in Applied Physics
Editorial Board of Physics International
Editorial Board of Quantum Physics Letters

Research stays

1990-1991 (12 months) Visiting Graduate Student under the guidance of Prof. Stephen M. Barnett at the Department of Engineering Science at the University of Oxford, U.K.
1989-2017 (altogether over 6 months) Ten research visits to Prof. J. Perina at the Department of Optics of Palacký University in Olomouc, Czech Republic.
1996 (a month) Research stay at the Quantum Information Group of Prof. Artur Ekert in the Clarendon Laboratory of the University of Oxford, U.K.
1997 (a month) Research visit to Prof. M.R.B. Wahiddin at the Institute of Mathematical Sciences of University of Malaya in Kuala Lumpur, Malaysia.
1998 (4 months) Study at the Osaka University of Foreign Studies (Osaka Gaikokugo Daigaku), Japan.
1998-2000 (20 months) Research stay in the lab of Prof. Hideaki Matsueda at the Department of Information Science, Kochi University, Japan.
2000-2001 (10+3 months) Two research stays in the CREST Research Team for Interacting Carrier Electronics headed by Prof. Nobuyuki Imoto at the Graduate University for Advanced Studies (SOKENDAI), Hayama, Japan.
2005-2009 (3 months) Five research stays within the SORST and 21st Century COE Programs by the invitation of the Japan Science and Technology Foundation in the group of Prof. Nobuyuki Imoto at Osaka University and in the group of Prof. Yoshiro Hirayama at NTT Basic Research Laboratories in Atsugi, Japan.
2005-2006 (4 months) Research stay by the invitation of Prof. Ryszard Horodecki within the EC IP SCALA and RESQ projects at the Quantum Information Group of the Institute of Theoretical Physics and Astrophysics, University of Gdańsk, Poland.
2006-2007 (4 months) Research stays by the invitation of Prof. Werner Vogel and Prof. Heinrich Stolz in Quantum Optics Group at Physics Institute of University of Rostock, Germany.
2006-2020 (about 40 months) Thirteen research stays by the invitation of Prof. Franco Nori at the Digital Materials Laboratory (DML) and then the Center for Emergent Matter Science (CEMS), RIKEN, Wako Campus, Saitama, Japan.

Awards

2019 – Wojciech Rubinowicz Award of the Polish Physical Society

Projects

Adam Miranowicz

Fundamental problems and implementations of dissipative quantum engineering

2020 - 2025, (NCN Maestro, No. 2019/34/A/ST2/00081, budget: 3 484 440 PLN ).

Abstract | Links

@misc{quant_eng,
title = {Fundamental problems and implementations of dissipative quantum engineering},
author = {Adam Miranowicz},
url = {http://zon8.physd.amu.edu.pl/~miran/grant-maestro-articles.html},
year = {2025},
date = {2025-04-14},
abstract = {The topic of this project is the theoretical analysis of dissipative quantum engineering, i.e., the generation, coherent control, and detection of quantum states in quantum nonlinear systems allowing for losses and gain. We focus on both fundamental aspects and implementations of such open quantum system dynamics. The latter is related to quantum technologies of the second generation, which process quantum information using quantum phenomena. Decay mechanisms, which are present in open systems and, thus, in all real devices, deteriorate the performance of quantum technologies. However, our preliminary results show that it is possible to find cases where the decay is desirable and useful in quantum information processing. We will try to find new ways to fully compensate for destructive effects of the decay or even to make the decay mechanisms playing a constructive role in quantum state engineering. Our approach is focused on dissipation-controlled quantum engineering of quantum analogs of standard (semiclassical) exceptional points (EPs), i.e., degeneracies of Hamiltonians describing non-Hermitian or PT-symmetric systems including the effect of quantum jumps (instantaneous switching between the energy levels of the system). EPs have been attracting increasing interest, both theoretical and experimental, in diverse fields of physical research. EPs are considered the basis for novel enhanced sensing apparatus and are relevant to describe dynamical phase transitions and in the characterization of topological phases of matter in open systems. However, it seems that the research community interested in PT-symmetric systems and EPs for quantum sensing ignores the effect of quantum jumps. In addition to including quantum jumps, we propose to define quantum EPs as degeneracies of Liouvillian superoperators. To our knowledge analyzing eigenspectra of Liouvillians in the contexts of the standard EPs, EP sensing, and PT-symmetric systems is a largely unexplored field of research. Quantum state engineering with dissipative nonlinear systems is a challenging problem also because such systems are often non-integrable. In this case it is useful to develop an algorithmic approach to dynamics in which one focuses not on equations of motion and notions like energy or momentum, but on iterative update rules and operational notions like change or translation. Thus, we will consider a concept of quantum cellular automata to simulate dynamics of dissipative quantum systems. Due to our collaborations with experimental physicists, who already implemented similar systems in their laboratories, we hope to experimentally verify at least some of our ideas. },
howpublished = {2020},
note = {NCN Maestro, No. 2019/34/A/ST2/00081, budget: 3 484 440 PLN },
keywords = {},
pubstate = {published},
tppubtype = {misc}
}

The topic of this project is the theoretical analysis of dissipative quantum engineering, i.e., the generation, coherent control, and detection of quantum states in quantum nonlinear systems allowing for losses and gain. We focus on both fundamental aspects and implementations of such open quantum system dynamics. The latter is related to quantum technologies of the second generation, which process quantum information using quantum phenomena. Decay mechanisms, which are present in open systems and, thus, in all real devices, deteriorate the performance of quantum technologies. However, our preliminary results show that it is possible to find cases where the decay is desirable and useful in quantum information processing. We will try to find new ways to fully compensate for destructive effects of the decay or even to make the decay mechanisms playing a constructive role in quantum state engineering. Our approach is focused on dissipation-controlled quantum engineering of quantum analogs of standard (semiclassical) exceptional points (EPs), i.e., degeneracies of Hamiltonians describing non-Hermitian or PT-symmetric systems including the effect of quantum jumps (instantaneous switching between the energy levels of the system). EPs have been attracting increasing interest, both theoretical and experimental, in diverse fields of physical research. EPs are considered the basis for novel enhanced sensing apparatus and are relevant to describe dynamical phase transitions and in the characterization of topological phases of matter in open systems. However, it seems that the research community interested in PT-symmetric systems and EPs for quantum sensing ignores the effect of quantum jumps. In addition to including quantum jumps, we propose to define quantum EPs as degeneracies of Liouvillian superoperators. To our knowledge analyzing eigenspectra of Liouvillians in the contexts of the standard EPs, EP sensing, and PT-symmetric systems is a largely unexplored field of research. Quantum state engineering with dissipative nonlinear systems is a challenging problem also because such systems are often non-integrable. In this case it is useful to develop an algorithmic approach to dynamics in which one focuses not on equations of motion and notions like energy or momentum, but on iterative update rules and operational notions like change or translation. Thus, we will consider a concept of quantum cellular automata to simulate dynamics of dissipative quantum systems. Due to our collaborations with experimental physicists, who already implemented similar systems in their laboratories, we hope to experimentally verify at least some of our ideas.

Publications

2024
37.	Ievgen I Arkhipov, Fabrizio Minganti, Adam Miranowicz, Şfiahin K ifmmode mboxŞelse Özdemir, Franco Nori Restoring Adiabatic State Transfer in Time-Modulated Non-Hermitian Systems Phys. Rev. Lett., 133 , pp. 113802, 2024. Links \| BibTeX @article{PhysRevLett.133.113802, title = {Restoring Adiabatic State Transfer in Time-Modulated Non-Hermitian Systems}, author = {Ievgen I Arkhipov and Fabrizio Minganti and Adam Miranowicz and Şfi{}ahin K ifmmode mbox{Ş}else Özdemir and Franco Nori}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.133.113802}, doi = {10.1103/PhysRevLett.133.113802}, year = {2024}, date = {2024-09-09}, journal = {Phys. Rev. Lett.}, volume = {133}, pages = {113802}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close https://link.aps.org/doi/10.1103/PhysRevLett.133.113802 doi:10.1103/PhysRevLett.133.113802 Close
36.	Josef Kadlec, Karol Bartkiewicz, Antonín Černoch, Karel Lemr, Adam Miranowicz Experimental relative entanglement potentials of single-photon states Phys. Rev. A, 110 , pp. 023720, 2024. Links \| BibTeX @article{PhysRevA.110.023720, title = {Experimental relative entanglement potentials of single-photon states}, author = {Josef Kadlec and Karol Bartkiewicz and Antonín Černoch and Karel Lemr and Adam Miranowicz}, url = {https://link.aps.org/doi/10.1103/PhysRevA.110.023720}, doi = {10.1103/PhysRevA.110.023720}, year = {2024}, date = {2024-08-01}, journal = {Phys. Rev. A}, volume = {110}, pages = {023720}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close https://link.aps.org/doi/10.1103/PhysRevA.110.023720 doi:10.1103/PhysRevA.110.023720 Close
35.	Deng-Gao Lai, C.-H. Wang, B.-P. Hou, Adam Miranowicz, Franco Nori Exceptional refrigeration of motions beyond their mass and temperature limitations Optica, 11 (4), pp. 485-491, 2024. Abstract \| Links \| BibTeX @article{Lai2024, title = {Exceptional refrigeration of motions beyond their mass and temperature limitations}, author = {Deng-Gao Lai and C.-H. Wang and B.-P. Hou and Adam Miranowicz and Franco Nori}, url = {https://opg.optica.org/optica/abstract.cfm?URI=optica-11-4-485}, doi = {10.1364/OPTICA.495199}, year = {2024}, date = {2024-04-08}, journal = {Optica}, volume = {11}, number = {4}, pages = {485-491}, abstract = {Coaxing vibrations in the regimes of both large mass and high temperature into their motional quantum ground states is extremely challenging, because it requires an ultra-high optical power, which introduces extraneous excessive heating and intricate instabilities. Here we propose how to overcome these obstacles and cool vibrational networks by simply harnessing the power of an exceptional point (EP) induced in parity-time symmetric structures; and we reveal its exceptional cooling properties otherwise unachievable in conventional devices. In stark contrast to standard-cooling protocols, a three orders-of-magnitude amplification in net cooling rates arises from the EP-cooling mechanism, without which it vanishes. Remarkably, our EP cooling is nearly immune to both resonator mass and environmental temperature, and this overthrows the consensus that poor intrinsic factors and rugged extrinsic environment suppress cooling channels. Our study offers the possibility of isolating and engineering motional properties of large-mass and high-temperature objects for various applications in optical and acoustic sensing, gravimetry, and inertial navigation.}, }, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Coaxing vibrations in the regimes of both large mass and high temperature into their motional quantum ground states is extremely challenging, because it requires an ultra-high optical power, which introduces extraneous excessive heating and intricate instabilities. Here we propose how to overcome these obstacles and cool vibrational networks by simply harnessing the power of an exceptional point (EP) induced in parity-time symmetric structures; and we reveal its exceptional cooling properties otherwise unachievable in conventional devices. In stark contrast to standard-cooling protocols, a three orders-of-magnitude amplification in net cooling rates arises from the EP-cooling mechanism, without which it vanishes. Remarkably, our EP cooling is nearly immune to both resonator mass and environmental temperature, and this overthrows the consensus that poor intrinsic factors and rugged extrinsic environment suppress cooling channels. Our study offers the possibility of isolating and engineering motional properties of large-mass and high-temperature objects for various applications in optical and acoustic sensing, gravimetry, and inertial navigation.}, Close https://opg.optica.org/optica/abstract.cfm?URI=optica-11-4-485 doi:10.1364/OPTICA.495199 Close
34.	Chia-Yi Ju, Adam Miranowicz, Yueh-Nan Chen, Guang-Yin Chen, Franco Nori Emergent parallel transport and curvature in Hermitian and non-Hermitian quantum mechanics Quantum, 8 , pp. 1277, 2024. Abstract \| Links \| BibTeX @article{Ju2024, title = {Emergent parallel transport and curvature in Hermitian and non-Hermitian quantum mechanics}, author = {Chia-Yi Ju and Adam Miranowicz and Yueh-Nan Chen and Guang-Yin Chen and Franco Nori}, url = {https://quantum-journal.org/papers/q-2024-03-13-1277/}, doi = {10.22331/q-2024-03-13-1277}, year = {2024}, date = {2024-03-13}, journal = {Quantum}, volume = {8}, pages = {1277}, abstract = {Studies have shown that the Hilbert spaces of non-Hermitian systems require nontrivial metrics. Here, we demonstrate how evolution dimensions, in addition to time, can emerge naturally from a geometric formalism. Specifically, in this formalism, Hamiltonians can be interpreted as a Christoffel symbol-like operators, and the Schroedinger equation as a parallel transport in this formalism. We then derive the evolution equations for the states and metrics along the emergent dimensions and find that the curvature of the Hilbert space bundle for any given closed system is locally flat. Finally, we show that the fidelity susceptibilities and the Berry curvatures of states are related to these emergent parallel transports.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Studies have shown that the Hilbert spaces of non-Hermitian systems require nontrivial metrics. Here, we demonstrate how evolution dimensions, in addition to time, can emerge naturally from a geometric formalism. Specifically, in this formalism, Hamiltonians can be interpreted as a Christoffel symbol-like operators, and the Schroedinger equation as a parallel transport in this formalism. We then derive the evolution equations for the states and metrics along the emergent dimensions and find that the curvature of the Hilbert space bundle for any given closed system is locally flat. Finally, we show that the fidelity susceptibilities and the Berry curvatures of states are related to these emergent parallel transports. Close https://quantum-journal.org/papers/q-2024-03-13-1277/ doi:10.22331/q-2024-03-13-1277 Close
33.	Arnab Laha, Adam Miranowicz, R. K. Varshney, Somnath Ghosh Correlated nonreciprocity around conjugate exceptional points Phys. Rev. A, 109 , pp. 033511, 2024. Abstract \| Links \| BibTeX @article{Laha2024, title = {Correlated nonreciprocity around conjugate exceptional points}, author = {Arnab Laha and Adam Miranowicz and R. K. Varshney and Somnath Ghosh}, url = {https://link.aps.org/doi/10.1103/PhysRevA.109.033511}, doi = {10.1103/PhysRevA.109.033511}, year = {2024}, date = {2024-03-08}, journal = {Phys. Rev. A}, volume = {109}, pages = {033511}, abstract = {The occurrence of exceptional points (EPs) is a fascinating non-Hermitian feature of open systems. A level-repulsion phenomenon between two complex states of an open system can be realized by positioning an EP and its time-reversal ( T ) conjugate pair in the underlying parameter space. Here, we report interesting nonreciprocal responses of such two conjugate EPs by using a dual-mode planar waveguide system having two T -symmetric active variants concerning the transverse gain-loss profiles. We specifically reveal an all-optical scheme to achieve correlative nonreciprocal light dynamics by using the reverse chirality of two dynamically encircled conjugate EPs in the presence of local nonlinearity. A specific nonreciprocal correlation between two designed T -symmetric waveguide variants is established in terms of their unidirectional transfer of light with a precise selection of modes. Here, the unconventional reverse chiral properties of two conjugate EPs allow the nonreciprocal transmission of two selective modes in the opposite directions of the underlying waveguide variants. An explicit dependence of the nonlinearity level on a significant enhancement of the nonreciprocity in terms of an isolation ratio is explored by investigating the effects of both local Kerr-type and saturable nonlinearities (considered separately). The physical insights and implications of harnessing the features of conjugate EPs in nonlinear optical systems can enable the growth and development of a versatile platform for building nonreciprocal components and devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close The occurrence of exceptional points (EPs) is a fascinating non-Hermitian feature of open systems. A level-repulsion phenomenon between two complex states of an open system can be realized by positioning an EP and its time-reversal ( T ) conjugate pair in the underlying parameter space. Here, we report interesting nonreciprocal responses of such two conjugate EPs by using a dual-mode planar waveguide system having two T -symmetric active variants concerning the transverse gain-loss profiles. We specifically reveal an all-optical scheme to achieve correlative nonreciprocal light dynamics by using the reverse chirality of two dynamically encircled conjugate EPs in the presence of local nonlinearity. A specific nonreciprocal correlation between two designed T -symmetric waveguide variants is established in terms of their unidirectional transfer of light with a precise selection of modes. Here, the unconventional reverse chiral properties of two conjugate EPs allow the nonreciprocal transmission of two selective modes in the opposite directions of the underlying waveguide variants. An explicit dependence of the nonlinearity level on a significant enhancement of the nonreciprocity in terms of an isolation ratio is explored by investigating the effects of both local Kerr-type and saturable nonlinearities (considered separately). The physical insights and implications of harnessing the features of conjugate EPs in nonlinear optical systems can enable the growth and development of a versatile platform for building nonreciprocal components and devices. Close https://link.aps.org/doi/10.1103/PhysRevA.109.033511 doi:10.1103/PhysRevA.109.033511 Close
32.	Wei Qin, Adam Miranowicz, Franco Nori Proposal of ensemble qubits with two-atom decay New Journal of Physics, 26 , pp. 033006, 2024. Abstract \| Links \| BibTeX @article{Qin2024, title = {Proposal of ensemble qubits with two-atom decay}, author = {Wei Qin and Adam Miranowicz and Franco Nori}, url = {https://iopscience.iop.org/article/10.1088/1367-2630/ad2bad}, doi = {10.1088/1367-2630/ad2bad}, year = {2024}, date = {2024-03-08}, journal = {New Journal of Physics}, volume = {26}, pages = {033006}, abstract = {We propose and analyze a novel approach to implement ensemble qubits. The required anharmonicity is provided by a simultaneous decay of two atoms (i.e. two-atom decay), which is achieved by fully quantum degenerate parametric amplification. For an atomic ensemble, the two-atom decay generates and stabilizes a 2D quantum manifold, which is spanned by the ground and single-excited superradiant states. Moreover, this nonlinear decay process can strongly suppress transitions to higher-excited superradiant states, and convert residual transitions into an effective decay from the single-excitation superradiant state to the ground state. Our method does not require Rydberg dipole blockade and, thus, strong atom-atom interactions, compared to previous work. This indicates that it can be applied to typical atomic or spin ensembles in simple experimental setups. Remarkably, our idea is compatible with the cavity protection mechanism, and therefore spin dephasing due to inhomogeneous broadening can be strongly suppressed. The presented ensemble qubit provides a new platform for quantum information processing, and also extends the range of applications of atomic or spin ensembles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose and analyze a novel approach to implement ensemble qubits. The required anharmonicity is provided by a simultaneous decay of two atoms (i.e. two-atom decay), which is achieved by fully quantum degenerate parametric amplification. For an atomic ensemble, the two-atom decay generates and stabilizes a 2D quantum manifold, which is spanned by the ground and single-excited superradiant states. Moreover, this nonlinear decay process can strongly suppress transitions to higher-excited superradiant states, and convert residual transitions into an effective decay from the single-excitation superradiant state to the ground state. Our method does not require Rydberg dipole blockade and, thus, strong atom-atom interactions, compared to previous work. This indicates that it can be applied to typical atomic or spin ensembles in simple experimental setups. Remarkably, our idea is compatible with the cavity protection mechanism, and therefore spin dephasing due to inhomogeneous broadening can be strongly suppressed. The presented ensemble qubit provides a new platform for quantum information processing, and also extends the range of applications of atomic or spin ensembles. Close https://iopscience.iop.org/article/10.1088/1367-2630/ad2bad doi:10.1088/1367-2630/ad2bad Close
31.	Marek Kopciuch, Magdalena Smolis, Adam Miranowicz, Szymon Pustelny Optimized optical tomography of quantum states of a room-temperature alkali-metal vapor Phys. Rev. A, 109 , pp. 032402, 2024. Abstract \| Links \| BibTeX @article{Kopciuch2024, title = {Optimized optical tomography of quantum states of a room-temperature alkali-metal vapor}, author = {Marek Kopciuch and Magdalena Smolis and Adam Miranowicz and Szymon Pustelny}, url = {https://link.aps.org/doi/10.1103/PhysRevA.109.032402}, doi = {10.1103/PhysRevA.109.032402}, year = {2024}, date = {2024-03-01}, journal = {Phys. Rev. A}, volume = {109}, pages = {032402}, abstract = {We demonstrate an experimental technique for the quantum-state tomography of the collective qutrit states of a room-temperature alkali-metal vapor. It is based on the measurements of the polarization of light traversing the vapor subjected to a magnetic field. To assess the technique's robustness against errors, experimental investigations are supported with numerical simulations. This not only allows us to determine the fidelity of the reconstructed states, but also to analyze the quality of the reconstruction for specific experimental parameters, such as light tuning and the number of measurements. By utilizing the conditional number, we demonstrate that the reconstruction robustness can be optimized by a proper adjustment of experimental parameters, and further improvement is possible with the repetition of specific measurements. Our results demonstrate the potential of this high-fidelity reconstruction method of quantum states of room-temperature atomic vapors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We demonstrate an experimental technique for the quantum-state tomography of the collective qutrit states of a room-temperature alkali-metal vapor. It is based on the measurements of the polarization of light traversing the vapor subjected to a magnetic field. To assess the technique's robustness against errors, experimental investigations are supported with numerical simulations. This not only allows us to determine the fidelity of the reconstructed states, but also to analyze the quality of the reconstruction for specific experimental parameters, such as light tuning and the number of measurements. By utilizing the conditional number, we demonstrate that the reconstruction robustness can be optimized by a proper adjustment of experimental parameters, and further improvement is possible with the repetition of specific measurements. Our results demonstrate the potential of this high-fidelity reconstruction method of quantum states of room-temperature atomic vapors. Close https://link.aps.org/doi/10.1103/PhysRevA.109.032402 doi:10.1103/PhysRevA.109.032402 Close
30.	Ye-Hong Chen, Yuan Qiu, Adam Miranowicz, Neill Lambert, Wei Qin, Roberto Stassi, Yan Xia, Shi-Biao Zheng, Franco Nori Sudden change of the photon output field marks phase transitions in the quantum Rabi model Communications Physics, 7 (5), 2024. Abstract \| Links \| BibTeX @article{Chen2024, title = {Sudden change of the photon output field marks phase transitions in the quantum Rabi model}, author = {Ye-Hong Chen and Yuan Qiu and Adam Miranowicz and Neill Lambert and Wei Qin and Roberto Stassi and Yan Xia and Shi-Biao Zheng and Franco Nori}, url = {https://www.nature.com/articles/s42005-023-01457-w}, doi = {10.1038/s42005-023-01457-w}, year = {2024}, date = {2024-01-05}, journal = {Communications Physics}, volume = {7}, number = {5}, abstract = {The experimental observation of quantum phase transitions predicted by the quantum Rabi model in quantum critical systems is usually challenging due to the lack of signature experimental observables associated with them. Here, we describe a method to identify the dynamical critical phenomenon in the quantum Rabi model consisting of a three-level atom and a cavity at the quantum phase transition. Such a critical phenomenon manifests itself as a sudden change of steady-state output photons in the system driven by two classical fields, when both the atom and the cavity are initially unexcited. The process occurs as the high-frequency pump field is converted into the low-frequency Stokes field and multiple cavity photons in the normal phase, while this conversion cannot occur in the superradiant phase. The sudden change of steady-state output photons is an experimentally accessible measure to probe quantum phase transitions, as it does not require preparing the equilibrium state.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close The experimental observation of quantum phase transitions predicted by the quantum Rabi model in quantum critical systems is usually challenging due to the lack of signature experimental observables associated with them. Here, we describe a method to identify the dynamical critical phenomenon in the quantum Rabi model consisting of a three-level atom and a cavity at the quantum phase transition. Such a critical phenomenon manifests itself as a sudden change of steady-state output photons in the system driven by two classical fields, when both the atom and the cavity are initially unexcited. The process occurs as the high-frequency pump field is converted into the low-frequency Stokes field and multiple cavity photons in the normal phase, while this conversion cannot occur in the superradiant phase. The sudden change of steady-state output photons is an experimentally accessible measure to probe quantum phase transitions, as it does not require preparing the equilibrium state. Close https://www.nature.com/articles/s42005-023-01457-w doi:10.1038/s42005-023-01457-w Close
29.	Josef Kadlec, Karol Bartkiewicz, Antonín Černoch, Karel Lemr, Adam Miranowicz Experimental hierarchy of the nonclassicality of single-qubit states via potentials for entanglement, steering, and Bell nonlocality Opt. Express, 32 (2), pp. 2333–2346, 2024. Abstract \| Links \| BibTeX @article{Kadlec:24, title = {Experimental hierarchy of the nonclassicality of single-qubit states via potentials for entanglement, steering, and Bell nonlocality}, author = {Josef Kadlec and Karol Bartkiewicz and Antonín Černoch and Karel Lemr and Adam Miranowicz}, url = {https://opg.optica.org/oe/abstract.cfm?URI=oe-32-2-2333}, doi = {10.1364/OE.506169}, year = {2024}, date = {2024-01-01}, journal = {Opt. Express}, volume = {32}, number = {2}, pages = {2333--2346}, publisher = {Optica Publishing Group}, abstract = {Entanglement potentials are a promising way to quantify the nonclassicality of single-mode states. They are defined by the amount of entanglement (expressed by, e.g., the Wootters concurrence) obtained after mixing the examined single-mode state with a purely classical state; such as the vacuum or a coherent state. We generalize the idea of entanglement potentials to other quantum correlations: the EPR steering and Bell nonlocality, thus enabling us to study mutual hierarchies of these nonclassicality potentials. Instead of the usual vacuum and one-photon superposition states, we experimentally test this concept using specially tailored polarization-encoded single-photon states. One polarization encodes a given nonclassical single-mode state, while the other serves as the vacuum place-holder. This technique proves to be experimentally more convenient in comparison to the vacuum and a one-photon superposition as it does not require the vacuum detection.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Entanglement potentials are a promising way to quantify the nonclassicality of single-mode states. They are defined by the amount of entanglement (expressed by, e.g., the Wootters concurrence) obtained after mixing the examined single-mode state with a purely classical state; such as the vacuum or a coherent state. We generalize the idea of entanglement potentials to other quantum correlations: the EPR steering and Bell nonlocality, thus enabling us to study mutual hierarchies of these nonclassicality potentials. Instead of the usual vacuum and one-photon superposition states, we experimentally test this concept using specially tailored polarization-encoded single-photon states. One polarization encodes a given nonclassical single-mode state, while the other serves as the vacuum place-holder. This technique proves to be experimentally more convenient in comparison to the vacuum and a one-photon superposition as it does not require the vacuum detection. Close https://opg.optica.org/oe/abstract.cfm?URI=oe-32-2-2333 doi:10.1364/OE.506169 Close
2023
28.	Ievgen I. Arkhipov, Adam Miranowicz, Franco Nori, Şahin K. Özdemir, Fabrizio Minganti Fully solvable finite simplex lattices with open boundaries in arbitrary dimensions Phys. Rev. Res., 5 , pp. 043092, 2023. Abstract \| Links \| BibTeX @article{Arkhipov2023b, title = {Fully solvable finite simplex lattices with open boundaries in arbitrary dimensions}, author = {Ievgen I. Arkhipov and Adam Miranowicz and Franco Nori and Şahin K. Özdemir and Fabrizio Minganti}, url = {https://link.aps.org/doi/10.1103/PhysRevResearch.5.043092}, doi = {10.1103/PhysRevResearch.5.043092}, year = {2023}, date = {2023-10-26}, journal = {Phys. Rev. Res.}, volume = {5}, pages = {043092}, abstract = {Finite simplex lattice models are used in different branches of science, e.g., in condensed-matter physics, when studying frustrated magnetic systems and non-Hermitian localization phenomena; or in chemistry, when describing experiments with mixtures. An n-simplex represents the simplest possible polytope in n dimensions, e.g., a line segment, a triangle, and a tetrahedron in one, two, and three dimensions, respectively. In this work, we show that various fully solvable, in general non-Hermitian, n-simplex lattice models with open boundaries can be constructed from the high-order field-moments space of quadratic bosonic systems. Namely, we demonstrate that such n-simplex lattices can be formed by a dimensional reduction of highly degenerate iterated polytope chains in (k>n)-dimensions, which naturally emerge in the field-moments space. Our findings indicate that the field-moments space of bosonic systems provides a versatile platform for simulating real-space n-simplex lattices exhibiting non-Hermitian phenomena, and it yields valuable insights into the structure of many-body systems exhibiting similar complexity. Among a variety of practical applications, these simplex structures can offer a physical setting for implementing the discrete fractional Fourier transform, an indispensable tool for both quantum and classical signal processing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Finite simplex lattice models are used in different branches of science, e.g., in condensed-matter physics, when studying frustrated magnetic systems and non-Hermitian localization phenomena; or in chemistry, when describing experiments with mixtures. An n-simplex represents the simplest possible polytope in n dimensions, e.g., a line segment, a triangle, and a tetrahedron in one, two, and three dimensions, respectively. In this work, we show that various fully solvable, in general non-Hermitian, n-simplex lattice models with open boundaries can be constructed from the high-order field-moments space of quadratic bosonic systems. Namely, we demonstrate that such n-simplex lattices can be formed by a dimensional reduction of highly degenerate iterated polytope chains in (k>n)-dimensions, which naturally emerge in the field-moments space. Our findings indicate that the field-moments space of bosonic systems provides a versatile platform for simulating real-space n-simplex lattices exhibiting non-Hermitian phenomena, and it yields valuable insights into the structure of many-body systems exhibiting similar complexity. Among a variety of practical applications, these simplex structures can offer a physical setting for implementing the discrete fractional Fourier transform, an indispensable tool for both quantum and classical signal processing. Close https://link.aps.org/doi/10.1103/PhysRevResearch.5.043092 doi:10.1103/PhysRevResearch.5.043092 Close
27.	Jan Peřina, Jr., Adam Miranowicz, Joanna K. Kalaga, Wiesław Leoński Unavoidability of nonclassicality loss in PT-symmetric systems Phys. Rev. A, 108 , pp. 033512, 2023. Abstract \| Links \| BibTeX @article{Peřina2023, title = {Unavoidability of nonclassicality loss in PT-symmetric systems}, author = {Jan Peřina, Jr. and Adam Miranowicz and Joanna K. Kalaga and Wiesław Leoński}, url = {https://journals.aps.org/pra/abstract/10.1103/PhysRevA.108.033512}, doi = {10.1103/PhysRevA.108.033512}, year = {2023}, date = {2023-09-15}, journal = {Phys. Rev. A}, volume = {108}, pages = {033512}, abstract = {We show that the loss of nonclassicality (including quantum entanglement) cannot be compensated by the (incoherent) amplification of PT-symmetric systems. We address this problem by manipulating the quantum fluctuating forces in the Heisenberg-Langevin approach. Specifically, we analyze the dynamics of two nonlinearly coupled oscillator modes in a PT-symmetric system. An analytical solution allows us to separate the contribution of reservoir fluctuations from the evolution of quantum statistical properties of the modes. In general, as reservoir fluctuations act constantly, the complete loss of nonclassicality and entanglement is observed for long times. To elucidate the role of reservoir fluctuations in a long-time evolution of nonclassicality and entanglement, we consider and compare the predictions from two alternative models in which no fatal long-time detrimental effects on the nonclassicality and entanglement are observed. This is so as, in the first semiclassical model, no reservoir fluctuations are considered at all. This, however, violates the fluctuation-dissipation theorem. The second, more elaborated, model obeys the fluctuation-dissipation relations as it partly involves reservoir fluctuations. However, to prevent the above long-time detrimental effects, the reservoir fluctuations have to be endowed with the nonphysical properties of a sink model. In both models, additional incorporation of the omitted reservoir fluctuations results in their physically consistent behavior. This behavior, however, predicts the gradual loss of the nonclassicality and entanglement. Thus the effects of reservoir fluctuations related to damping cannot be compensated by those related to amplification. This qualitatively differs from the influence of damping and amplification to a direct coherent dynamics of PT-symmetric systems in which their mutual interference results in a periodic behavior allowing for nonclassicality and entanglement at arbitrary times.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We show that the loss of nonclassicality (including quantum entanglement) cannot be compensated by the (incoherent) amplification of PT-symmetric systems. We address this problem by manipulating the quantum fluctuating forces in the Heisenberg-Langevin approach. Specifically, we analyze the dynamics of two nonlinearly coupled oscillator modes in a PT-symmetric system. An analytical solution allows us to separate the contribution of reservoir fluctuations from the evolution of quantum statistical properties of the modes. In general, as reservoir fluctuations act constantly, the complete loss of nonclassicality and entanglement is observed for long times. To elucidate the role of reservoir fluctuations in a long-time evolution of nonclassicality and entanglement, we consider and compare the predictions from two alternative models in which no fatal long-time detrimental effects on the nonclassicality and entanglement are observed. This is so as, in the first semiclassical model, no reservoir fluctuations are considered at all. This, however, violates the fluctuation-dissipation theorem. The second, more elaborated, model obeys the fluctuation-dissipation relations as it partly involves reservoir fluctuations. However, to prevent the above long-time detrimental effects, the reservoir fluctuations have to be endowed with the nonphysical properties of a sink model. In both models, additional incorporation of the omitted reservoir fluctuations results in their physically consistent behavior. This behavior, however, predicts the gradual loss of the nonclassicality and entanglement. Thus the effects of reservoir fluctuations related to damping cannot be compensated by those related to amplification. This qualitatively differs from the influence of damping and amplification to a direct coherent dynamics of PT-symmetric systems in which their mutual interference results in a periodic behavior allowing for nonclassicality and entanglement at arbitrary times. Close https://journals.aps.org/pra/abstract/10.1103/PhysRevA.108.033512 doi:10.1103/PhysRevA.108.033512 Close
26.	Ri-Hua Zheng, Wen Ning, Ye-Hong Chen, Jia-Hao Lü, Li-Tuo Shen, Kai Xu, Yu-Ran Zhang, Da Xu, Hekang Li, Yan Xia, Fan Wu, Zhen-Biao Yang, Adam Miranowicz, Neill Lambert, Dongning Zheng, Heng Fan, Franco Nori, Shi-Biao Zheng Observation of a Superradiant Phase Transition with Emergent Cat States Phys. Rev. Lett., 131 , pp. 113601 , 2023. Abstract \| Links \| BibTeX @article{Zheng2023, title = {Observation of a Superradiant Phase Transition with Emergent Cat States}, author = {Ri-Hua Zheng and Wen Ning and Ye-Hong Chen and Jia-Hao Lü and Li-Tuo Shen and Kai Xu and Yu-Ran Zhang and Da Xu and Hekang Li and Yan Xia and Fan Wu and Zhen-Biao Yang and Adam Miranowicz and Neill Lambert and Dongning Zheng and Heng Fan and Franco Nori and Shi-Biao Zheng}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.113601}, doi = {10.1103/PhysRevLett.131.113601}, year = {2023}, date = {2023-09-11}, journal = {Phys. Rev. Lett.}, volume = {131}, pages = {113601 }, abstract = {Superradiant phase transitions (SPTs) are important for understanding light-matter interactions at the quantum level, and play a central role in criticality-enhanced quantum sensing. So far, SPTs have been observed in driven-dissipative systems, but the emergent light fields did not show any nonclassical characteristic due to the presence of strong dissipation. Here we report an experimental demonstration of the SPT featuring the emergence of a highly nonclassical photonic field, realized with a resonator coupled to a superconducting qubit, implementing the quantum Rabi model. We fully characterize the light-matter state by Wigner matrix tomography. The measured matrix elements exhibit quantum interference intrinsic of a photonic mesoscopic superposition, and reveal light-matter entanglement.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Superradiant phase transitions (SPTs) are important for understanding light-matter interactions at the quantum level, and play a central role in criticality-enhanced quantum sensing. So far, SPTs have been observed in driven-dissipative systems, but the emergent light fields did not show any nonclassical characteristic due to the presence of strong dissipation. Here we report an experimental demonstration of the SPT featuring the emergence of a highly nonclassical photonic field, realized with a resonator coupled to a superconducting qubit, implementing the quantum Rabi model. We fully characterize the light-matter state by Wigner matrix tomography. The measured matrix elements exhibit quantum interference intrinsic of a photonic mesoscopic superposition, and reveal light-matter entanglement. Close https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.113601 doi:10.1103/PhysRevLett.131.113601 Close
25.	Shilan Abo, Jan Soubusta, Kateřina Jiráková, Karol Bartkiewicz, Antonín Černoch, Karel Lemr, Adam Miranowicz Experimental hierarchy of two-qubit quantum correlations without state tomography Scientific Reports, 13 (1), pp. 8564, 2023, ISSN: 2045-2322. Abstract \| Links \| BibTeX @article{abo_experimental_2023, title = {Experimental hierarchy of two-qubit quantum correlations without state tomography}, author = {Shilan Abo and Jan Soubusta and Kateřina Jiráková and Karol Bartkiewicz and Antonín Černoch and Karel Lemr and Adam Miranowicz}, url = {https://www.nature.com/articles/s41598-023-35015-9}, doi = {10.1038/s41598-023-35015-9}, issn = {2045-2322}, year = {2023}, date = {2023-05-26}, urldate = {2023-10-18}, journal = {Scientific Reports}, volume = {13}, number = {1}, pages = {8564}, abstract = {A Werner state, which is the singlet Bell state affected by white noise, is a prototype example of states, which can reveal a hierarchy of quantum entanglement, steering, and Bell nonlocality by controlling the amount of noise. However, experimental demonstrations of this hierarchy in a sufficient and necessary way (i.e., by applying measures or universal witnesses of these quantum correlations) have been mainly based on full quantum state tomography, corresponding to measuring at least 15 real parameters of two-qubit states. Here we report an experimental demonstration of this hierarchy by measuring only six elements of a correlation matrix depending on linear combinations of two-qubit Stokes parameters. We show that our experimental setup can also reveal the hierarchy of these quantum correlations of generalized Werner states, which are any two-qubit pure states affected by white noise.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close A Werner state, which is the singlet Bell state affected by white noise, is a prototype example of states, which can reveal a hierarchy of quantum entanglement, steering, and Bell nonlocality by controlling the amount of noise. However, experimental demonstrations of this hierarchy in a sufficient and necessary way (i.e., by applying measures or universal witnesses of these quantum correlations) have been mainly based on full quantum state tomography, corresponding to measuring at least 15 real parameters of two-qubit states. Here we report an experimental demonstration of this hierarchy by measuring only six elements of a correlation matrix depending on linear combinations of two-qubit Stokes parameters. We show that our experimental setup can also reveal the hierarchy of these quantum correlations of generalized Werner states, which are any two-qubit pure states affected by white noise. Close https://www.nature.com/articles/s41598-023-35015-9 doi:10.1038/s41598-023-35015-9 Close
24.	Ievgen I. Arkhipov, Adam Miranowicz, Fabrizio Minganti, Şahin K. Özdemir, Franco Nori Dynamically crossing diabolic points while encircling exceptional curves: A programmable symmetric-asymmetric multimode switch Nature Communications, 14 (2076), 2023. Abstract \| Links \| BibTeX @article{Arkhipov2023, title = {Dynamically crossing diabolic points while encircling exceptional curves: A programmable symmetric-asymmetric multimode switch}, author = {Ievgen I. Arkhipov and Adam Miranowicz and Fabrizio Minganti and Şahin K. Özdemir and Franco Nori}, url = {https://www.nature.com/articles/s41467-023-37275-5}, doi = {doi.org/10.1038/s41467-023-37275-5}, year = {2023}, date = {2023-04-12}, journal = {Nature Communications}, volume = {14}, number = {2076}, abstract = {Nontrivial spectral properties of non-Hermitian systems can lead to intriguing effects with no counterparts in Hermitian systems. For instance, in a two-mode photonic system, by dynamically winding around an exceptional point (EP) a controlled asymmetric-symmetric mode switching can be realized. That is, the system can either end up in one of its eigenstates, regardless of the initial eigenmode, or it can switch between the two states on demand, by simply controlling the winding direction. However, for multimode systems with higher-order EPs or multiple low-order EPs, the situation can be more involved, and the ability to control asymmetric-symmetric mode switching can be impeded, due to the breakdown of adiabaticity. Here we demonstrate that this difficulty can be overcome by winding around exceptional curves by additionally crossing diabolic points. We consider a four-mode PT-symmetric bosonic system as a platform for experimental realization of such a multimode switch. Our work provides alternative routes for light manipulations in non-Hermitian photonic setups.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Nontrivial spectral properties of non-Hermitian systems can lead to intriguing effects with no counterparts in Hermitian systems. For instance, in a two-mode photonic system, by dynamically winding around an exceptional point (EP) a controlled asymmetric-symmetric mode switching can be realized. That is, the system can either end up in one of its eigenstates, regardless of the initial eigenmode, or it can switch between the two states on demand, by simply controlling the winding direction. However, for multimode systems with higher-order EPs or multiple low-order EPs, the situation can be more involved, and the ability to control asymmetric-symmetric mode switching can be impeded, due to the breakdown of adiabaticity. Here we demonstrate that this difficulty can be overcome by winding around exceptional curves by additionally crossing diabolic points. We consider a four-mode PT-symmetric bosonic system as a platform for experimental realization of such a multimode switch. Our work provides alternative routes for light manipulations in non-Hermitian photonic setups. Close https://www.nature.com/articles/s41467-023-37275-5 doi:doi.org/10.1038/s41467-023-37275-5 Close
23.	Alberto Mercurio, Shilan Abo, Fabio Mauceri, Enrico Russo, Vincenzo Macrì, Adam Miranowicz, Salvatore Savasta, Omar Di Stefano Pure Dephasing of Light-Matter Systems in the Ultrastrong and Deep-Strong Coupling Regimes Phys. Rev. Lett., 130 , pp. 123601, 2023. Abstract \| Links \| BibTeX @article{Mercurio2023, title = {Pure Dephasing of Light-Matter Systems in the Ultrastrong and Deep-Strong Coupling Regimes}, author = {Alberto Mercurio and Shilan Abo and Fabio Mauceri and Enrico Russo and Vincenzo Macrì and Adam Miranowicz and Salvatore Savasta and Omar Di Stefano}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.130.123601}, doi = {10.1103/PhysRevLett.130.123601}, year = {2023}, date = {2023-03-21}, journal = {Phys. Rev. Lett.}, volume = {130}, pages = {123601}, abstract = {Pure dephasing originates from the nondissipative information exchange between quantum systems and environments, and plays a key role in both spectroscopy and quantum information technology. Often pure dephasing constitutes the main mechanism of decay of quantum correlations. Here we investigate how pure dephasing of one of the components of a hybrid quantum system affects the dephasing rate of the system transitions. We find that, in turn, the interaction, in the case of a light-matter system, can significantly affect the form of the stochastic perturbation describing the dephasing of a subsystem, depending on the adopted gauge. Neglecting this issue can lead to wrong and unphysical results when the interaction becomes comparable to the bare resonance frequencies of subsystems, which correspond to the ultrastrong and deep-strong coupling regimes. We present results for two prototypical models of cavity quantun electrodynamics: the quantum Rabi and the Hopfield model.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Pure dephasing originates from the nondissipative information exchange between quantum systems and environments, and plays a key role in both spectroscopy and quantum information technology. Often pure dephasing constitutes the main mechanism of decay of quantum correlations. Here we investigate how pure dephasing of one of the components of a hybrid quantum system affects the dephasing rate of the system transitions. We find that, in turn, the interaction, in the case of a light-matter system, can significantly affect the form of the stochastic perturbation describing the dephasing of a subsystem, depending on the adopted gauge. Neglecting this issue can lead to wrong and unphysical results when the interaction becomes comparable to the bare resonance frequencies of subsystems, which correspond to the ultrastrong and deep-strong coupling regimes. We present results for two prototypical models of cavity quantun electrodynamics: the quantum Rabi and the Hopfield model. Close https://link.aps.org/doi/10.1103/PhysRevLett.130.123601 doi:10.1103/PhysRevLett.130.123601 Close
22.	Kuan-Yi Lee, Jhen-Dong Lin, Adam Miranowicz, Franco Nori, Huan-Yu Ku, Yueh-Nan Chen Steering-enhanced quantum metrology using superpositions of noisy phase shifts Phys. Rev. Res., 5 , pp. 013103, 2023. Abstract \| Links \| BibTeX @article{23prr-lee, title = {Steering-enhanced quantum metrology using superpositions of noisy phase shifts}, author = {Kuan-Yi Lee and Jhen-Dong Lin and Adam Miranowicz and Franco Nori and Huan-Yu Ku and Yueh-Nan Chen}, url = {https://link.aps.org/doi/10.1103/PhysRevResearch.5.013103}, doi = {10.1103/PhysRevResearch.5.013103}, year = {2023}, date = {2023-02-13}, journal = {Phys. Rev. Res.}, volume = {5}, pages = {013103}, publisher = {American Physical Society}, abstract = {Quantum steering is an important correlation in quantum information theory. A recent work [Nat. Commun. 12, 2410 (2021)] showed that quantum steering is also useful for quantum metrology. Here, we extend the exploration of steering-enhanced quantum metrology from single noiseless phase shifts to superpositions of noisy phase shifts. As concrete examples, we consider a control system that manipulates a target system to pass through a superposition of either dephased or depolarized phase shifts channels. We show that using such superpositions of noisy phase shifts can suppress the effects of noise and improve metrology. Furthermore, we also implemented proof-of-principle experiments for a superposition of dephased phase shifts on the IBM quantum experience, demonstrating a clear improvement on metrology.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Quantum steering is an important correlation in quantum information theory. A recent work [Nat. Commun. 12, 2410 (2021)] showed that quantum steering is also useful for quantum metrology. Here, we extend the exploration of steering-enhanced quantum metrology from single noiseless phase shifts to superpositions of noisy phase shifts. As concrete examples, we consider a control system that manipulates a target system to pass through a superposition of either dephased or depolarized phase shifts channels. We show that using such superpositions of noisy phase shifts can suppress the effects of noise and improve metrology. Furthermore, we also implemented proof-of-principle experiments for a superposition of dephased phase shifts on the IBM quantum experience, demonstrating a clear improvement on metrology. Close https://link.aps.org/doi/10.1103/PhysRevResearch.5.013103 doi:10.1103/PhysRevResearch.5.013103 Close
2022
21.	Ye-Hong Chen, Adam Miranowicz, Xi Chen, Yan Xia, Franco Nori Enhanced-Fidelity Ultrafast Geometric Quantum Computation Using Strong Classical Drives Phys. Rev. Appl., 18 , pp. 064059, 2022. Abstract \| Links \| BibTeX @article{Chen22geom, title = {Enhanced-Fidelity Ultrafast Geometric Quantum Computation Using Strong Classical Drives}, author = {Ye-Hong Chen and Adam Miranowicz and Xi Chen and Yan Xia and Franco Nori}, url = {https://link.aps.org/doi/10.1103/PhysRevApplied.18.064059}, doi = {10.1103/PhysRevApplied.18.064059}, year = {2022}, date = {2022-12-20}, journal = {Phys. Rev. Appl.}, volume = {18}, pages = {064059}, publisher = {American Physical Society}, abstract = {We propose a general approach to implement ultrafast nonadiabatic geometric single- and two-qubit gates by employing counter-rotating effects. This protocol is compatible with most optimal control methods used in previous rotating-wave approximation (RWA) protocols; thus, it is as robust as (or even more robust than) the RWA protocols. Using counter-rotating effects allows us to apply strong drives. Therefore, we can improve the gate speed by 5–10 times compared to the RWA counterpart for implementing high-fidelity (≥99.99%) gates. Such an ultrafast evolution (nanoseconds, even picoseconds) significantly reduces the influence of decoherence (e.g., the qubit dissipation and dephasing). Moreover, because the counter-rotating effects no longer induce a gate infidelity (in both the weak and strong driving regimes), we can achieve a higher fidelity compared to the RWA protocols. Therefore, in the presence of decoherence, one can implement ultrafast geometric quantum gates with ≥99% fidelities.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose a general approach to implement ultrafast nonadiabatic geometric single- and two-qubit gates by employing counter-rotating effects. This protocol is compatible with most optimal control methods used in previous rotating-wave approximation (RWA) protocols; thus, it is as robust as (or even more robust than) the RWA protocols. Using counter-rotating effects allows us to apply strong drives. Therefore, we can improve the gate speed by 5–10 times compared to the RWA counterpart for implementing high-fidelity (≥99.99%) gates. Such an ultrafast evolution (nanoseconds, even picoseconds) significantly reduces the influence of decoherence (e.g., the qubit dissipation and dephasing). Moreover, because the counter-rotating effects no longer induce a gate infidelity (in both the weak and strong driving regimes), we can achieve a higher fidelity compared to the RWA protocols. Therefore, in the presence of decoherence, one can implement ultrafast geometric quantum gates with ≥99% fidelities. Close https://link.aps.org/doi/10.1103/PhysRevApplied.18.064059 doi:10.1103/PhysRevApplied.18.064059 Close
20.	Jan Perina Jr, Adam Miranowicz, Grzegorz Chimczak, Anna Kowalewska-Kudłaszyk Quantum Liouvillian exceptional and diabolical points for bosonic fields with quadratic Ħamiltonians: Ŧhe Ħeisenberg-Langevin equation approach Quantum, 6 , pp. 883, 2022, ISSN: 2521-327X. Abstract \| Links \| BibTeX @article{Perina2022quantum, title = {Quantum Liouvillian exceptional and diabolical points for bosonic fields with quadratic Ħamiltonians: Ŧhe Ħeisenberg-Langevin equation approach}, author = {Jan Perina Jr and Adam Miranowicz and Grzegorz Chimczak and Anna Kowalewska-Kudłaszyk}, url = {https://doi.org/10.22331/q-2022-12-22-883}, doi = {10.22331/q-2022-12-22-883}, issn = {2521-327X}, year = {2022}, date = {2022-12-10}, journal = {Quantum}, volume = {6}, pages = {883}, publisher = {Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften}, abstract = {Equivalent approaches to determine eigenfrequencies of the Liouvillians of open quantum systems are discussed using the solution of the Heisenberg-Langevin equations and the corresponding equations for operator moments. A simple damped two-level atom is analyzed to demonstrate the equivalence of both approaches. The suggested method is used to reveal the structure as well as eigenfrequencies of the dynamics matrices of the corresponding equations of motion and their degeneracies for interacting bosonic modes described by general quadratic Hamiltonians. Quantum Liouvillian exceptional and diabolical points and their degeneracies are explicitly discussed for the case of two modes. Quantum hybrid diabolical exceptional points (inherited, genuine, and induced) and hidden exceptional points, which are not recognized directly in amplitude spectra, are observed. The presented approach via the Heisenberg-Langevin equations paves the general way to a detailed analysis of quantum exceptional and diabolical points in infinitely dimensional open quantum systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Equivalent approaches to determine eigenfrequencies of the Liouvillians of open quantum systems are discussed using the solution of the Heisenberg-Langevin equations and the corresponding equations for operator moments. A simple damped two-level atom is analyzed to demonstrate the equivalence of both approaches. The suggested method is used to reveal the structure as well as eigenfrequencies of the dynamics matrices of the corresponding equations of motion and their degeneracies for interacting bosonic modes described by general quadratic Hamiltonians. Quantum Liouvillian exceptional and diabolical points and their degeneracies are explicitly discussed for the case of two modes. Quantum hybrid diabolical exceptional points (inherited, genuine, and induced) and hidden exceptional points, which are not recognized directly in amplitude spectra, are observed. The presented approach via the Heisenberg-Langevin equations paves the general way to a detailed analysis of quantum exceptional and diabolical points in infinitely dimensional open quantum systems. Close https://doi.org/10.22331/q-2022-12-22-883 doi:10.22331/q-2022-12-22-883 Close
19.	Shilan Abo, Grzegorz Chimczak, Anna Kowalewska-Kudłaszyk, Jan Peřina Jr, Ravindra W. Chhajlany, Adam Miranowicz Hybrid photon–phonon blockade Scientific Reports, 12 , pp. 17655, 2022, ISSN: 2045-2322. Abstract \| Links \| BibTeX @article{shilan2022, title = {Hybrid photon–phonon blockade}, author = {Shilan Abo and Grzegorz Chimczak and Anna Kowalewska-Kudłaszyk and Jan Peřina Jr and Ravindra W. Chhajlany and Adam Miranowicz }, url = {https://www.nature.com/articles/s41598-022-21267-4}, doi = {https://doi.org/10.1038/s41598-022-21267-4}, issn = {2045-2322}, year = {2022}, date = {2022-10-21}, journal = {Scientific Reports}, volume = {12}, pages = {17655}, abstract = {We describe a novel type of blockade in a hybrid mode generated by linear coupling of photonic and phononic modes. We refer to this effect as hybrid photon–phonon blockade and show how it can be generated and detected in a driven nonlinear optomechanical superconducting system. Thus, we study boson-number correlations in the photon, phonon, and hybrid modes in linearly coupled microwave and mechanical resonators with a superconducting qubit inserted in one of them. We find such system parameters for which we observe eight types of different combinations of either blockade or tunnelling effects (defined via the sub- and super-Poissonian statistics, respectively) for photons, phonons, and hybrid bosons. In particular, we find that the hybrid photon–phonon blockade can be generated by mixing the photonic and phononic modes which do not exhibit blockade.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We describe a novel type of blockade in a hybrid mode generated by linear coupling of photonic and phononic modes. We refer to this effect as hybrid photon–phonon blockade and show how it can be generated and detected in a driven nonlinear optomechanical superconducting system. Thus, we study boson-number correlations in the photon, phonon, and hybrid modes in linearly coupled microwave and mechanical resonators with a superconducting qubit inserted in one of them. We find such system parameters for which we observe eight types of different combinations of either blockade or tunnelling effects (defined via the sub- and super-Poissonian statistics, respectively) for photons, phonons, and hybrid bosons. In particular, we find that the hybrid photon–phonon blockade can be generated by mixing the photonic and phononic modes which do not exhibit blockade. Close https://www.nature.com/articles/s41598-022-21267-4 doi:https://doi.org/10.1038/s41598-022-21267-4 Close
18.	Wei Qin, Adam Miranowicz, Franco Nori Beating the 3 dB Limit for Intracavity Squeezing and Its Application to Nondemolition Qubit Readout Phys. Rev. Lett., 129 , pp. 123602, 2022. Abstract \| Links \| BibTeX @article{Qin2022, title = {Beating the 3 dB Limit for Intracavity Squeezing and Its Application to Nondemolition Qubit Readout}, author = {Wei Qin and Adam Miranowicz and Franco Nori}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.123602}, doi = {10.1103/PhysRevLett.129.123602}, year = {2022}, date = {2022-09-14}, journal = {Phys. Rev. Lett.}, volume = {129}, pages = {123602}, abstract = {While the squeezing of a propagating field can, in principle, be made arbitrarily strong, the cavity-field squeezing is subject to the well-known 3 dB limit, and thus has limited applications. Here, we propose the use of a fully quantum degenerate parametric amplifier (DPA) to beat this squeezing limit. Specifically, we show that by simply applying a two-tone driving to the signal mode, the pump mode can, counterintuitively, be driven by the photon loss of the signal mode into a squeezed steady state with, in principle, an arbitrarily high degree of squeezing. Furthermore, we demonstrate that this intracavity squeezing can increase the signal-to-noise ratio of longitudinal qubit readout exponentially with the degree of squeezing. Correspondingly, an improvement of the measurement error by many orders of magnitude can be achieved even for modest parameters. In stark contrast, using intracavity squeezing of the semiclassical DPA cannot practically increase the signal-to-noise ratio and thus improve the measurement error. Our results extend the range of applications of DPAs and open up new opportunities for modern quantum technologies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close While the squeezing of a propagating field can, in principle, be made arbitrarily strong, the cavity-field squeezing is subject to the well-known 3 dB limit, and thus has limited applications. Here, we propose the use of a fully quantum degenerate parametric amplifier (DPA) to beat this squeezing limit. Specifically, we show that by simply applying a two-tone driving to the signal mode, the pump mode can, counterintuitively, be driven by the photon loss of the signal mode into a squeezed steady state with, in principle, an arbitrarily high degree of squeezing. Furthermore, we demonstrate that this intracavity squeezing can increase the signal-to-noise ratio of longitudinal qubit readout exponentially with the degree of squeezing. Correspondingly, an improvement of the measurement error by many orders of magnitude can be achieved even for modest parameters. In stark contrast, using intracavity squeezing of the semiclassical DPA cannot practically increase the signal-to-noise ratio and thus improve the measurement error. Our results extend the range of applications of DPAs and open up new opportunities for modern quantum technologies. Close https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.123602 doi:10.1103/PhysRevLett.129.123602 Close
17.	Rui Xu, Deng-Gao Lai, Bang-Pin Hou, Adam Miranowicz, Franco Nori Millionfold improvement in multivibration-feedback optomechanical refrigeration via auxiliary mechanical coupling Phys. Rev. A, 106 , pp. 033509, 2022. Abstract \| Links \| BibTeX @article{Xu2022, title = {Millionfold improvement in multivibration-feedback optomechanical refrigeration via auxiliary mechanical coupling}, author = {Rui Xu and Deng-Gao Lai and Bang-Pin Hou and Adam Miranowicz and Franco Nori}, url = {https://journals.aps.org/pra/abstract/10.1103/PhysRevA.106.033509}, doi = {10.1103/PhysRevA.106.033509}, year = {2022}, date = {2022-09-13}, journal = {Phys. Rev. A}, volume = {106}, pages = {033509}, abstract = {The simultaneous ground-state refrigeration of multiple vibrational modes is a prerequisite for observing significant quantum effects of multiple-vibration systems. Here we propose how to realize a large amplification in the net-refrigeration rates based on cavity optomechanics and to largely improve the cooling performance of multivibration modes beyond the resolved-sideband regime. By employing an auxiliary mechanical coupling (AMC) between two mechanical vibrations, the dark mode, which is induced by the coupling of these vibrational modes to a common optical mode and cuts off cooling channels, can be fully removed. We use fully analytical treatments for the effective mechanical susceptibilities and net-cooling rates and find that when the AMC is turned on, the amplification of the net-refrigeration rates by more than six orders of magnitude can be observed. In particular, we reveal that the simultaneous ground-state cooling beyond the resolved-sideband regime arises from the introduced AMC, without which it vanishes. Our work paves the way for quantum control of multiple vibrational modes in the bad-cavity regime.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close The simultaneous ground-state refrigeration of multiple vibrational modes is a prerequisite for observing significant quantum effects of multiple-vibration systems. Here we propose how to realize a large amplification in the net-refrigeration rates based on cavity optomechanics and to largely improve the cooling performance of multivibration modes beyond the resolved-sideband regime. By employing an auxiliary mechanical coupling (AMC) between two mechanical vibrations, the dark mode, which is induced by the coupling of these vibrational modes to a common optical mode and cuts off cooling channels, can be fully removed. We use fully analytical treatments for the effective mechanical susceptibilities and net-cooling rates and find that when the AMC is turned on, the amplification of the net-refrigeration rates by more than six orders of magnitude can be observed. In particular, we reveal that the simultaneous ground-state cooling beyond the resolved-sideband regime arises from the introduced AMC, without which it vanishes. Our work paves the way for quantum control of multiple vibrational modes in the bad-cavity regime. Close https://journals.aps.org/pra/abstract/10.1103/PhysRevA.106.033509 doi:10.1103/PhysRevA.106.033509 Close
16.	Ye-Hong Chen, Roberto Stassi, Wei Qin, Adam Miranowicz, Franco Nori Fault-Tolerant Multiqubit Geometric Entangling Gates Using Photonic Cat-State Qubits Phys. Rev. Applied, 18 , pp. 024076, 2022. Abstract \| Links \| BibTeX @article{Chen2022, title = {Fault-Tolerant Multiqubit Geometric Entangling Gates Using Photonic Cat-State Qubits}, author = {Ye-Hong Chen and Roberto Stassi and Wei Qin and Adam Miranowicz and Franco Nori}, url = {https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.18.024076}, doi = {10.1103/PhysRevApplied.18.024076}, year = {2022}, date = {2022-08-29}, journal = {Phys. Rev. Applied}, volume = {18}, pages = {024076}, abstract = {We propose a theoretical protocol to implement multiqubit geometric gates (i.e., the Mølmer-Sørensen gate) using photonic cat-state qubits. These cat-state qubits stored in high-Q resonators are promising for hardware-efficient universal quantum computing. Specifically, in the limit of strong two-photon drivings, phase-flip errors of the cat-state qubits are effectively suppressed, leaving only a bit-flip error to be corrected. Because this dominant error commutes with the evolution operator, our protocol preserves the error bias, and, thus, can lower the code-capacity threshold for error correction. A geometric evolution guarantees the robustness of the protocol against stochastic noise along the evolution path. Moreover, by changing detunings of the cavity-cavity couplings at a proper time, the protocol can be robust against parameter imperfections (e.g., the total evolution time) without introducing extra noises into the system. As a result, the gate can produce multimode entangled cat states in a short time with high fidelities.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose a theoretical protocol to implement multiqubit geometric gates (i.e., the Mølmer-Sørensen gate) using photonic cat-state qubits. These cat-state qubits stored in high-Q resonators are promising for hardware-efficient universal quantum computing. Specifically, in the limit of strong two-photon drivings, phase-flip errors of the cat-state qubits are effectively suppressed, leaving only a bit-flip error to be corrected. Because this dominant error commutes with the evolution operator, our protocol preserves the error bias, and, thus, can lower the code-capacity threshold for error correction. A geometric evolution guarantees the robustness of the protocol against stochastic noise along the evolution path. Moreover, by changing detunings of the cavity-cavity couplings at a proper time, the protocol can be robust against parameter imperfections (e.g., the total evolution time) without introducing extra noises into the system. As a result, the gate can produce multimode entangled cat states in a short time with high fidelities. Close https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.18.024076 doi:10.1103/PhysRevApplied.18.024076 Close
15.	Deng-Gao Lai, Ye-Hong Chen, Wei Qin, Adam Miranowicz, Franco Nori Tripartite optomechanical entanglement via optical-dark-mode control Phys. Rev. Research, 4 , pp. 033112, 2022. Abstract \| Links \| BibTeX @article{Lai2022, title = {Tripartite optomechanical entanglement via optical-dark-mode control}, author = {Deng-Gao Lai and Ye-Hong Chen and Wei Qin and Adam Miranowicz and Franco Nori}, url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.033112}, doi = {10.1103/PhysRevResearch.4.033112}, year = {2022}, date = {2022-08-10}, journal = {Phys. Rev. Research}, volume = {4}, pages = {033112}, abstract = {We propose how to generate a tripartite light-vibration entanglement by controlling an optical dark mode (ODM), which is induced by the coupling of two optical modes to a common vibrational mode. This ODM is decoupled from the vibration, and it can be controlled on demand by employing a synthetic gauge field, which can enable efficient switching between the ODM-unbreaking and ODM-breaking regimes. We find that the tripartite optomechanical entanglement is largely suppressed in the ODM-unbreaking regime, but it is significantly enhanced in the ODM-breaking regime. In particular, the noise robustness of quantum entanglement in the ODM-breaking regime can be more than twice than that in the ODM-unbreaking regime. This study offers a method for protecting and enhancing fragile quantum resources and for constructing noise-tolerant and dark-mode-immune quantum processors and entangled networks.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose how to generate a tripartite light-vibration entanglement by controlling an optical dark mode (ODM), which is induced by the coupling of two optical modes to a common vibrational mode. This ODM is decoupled from the vibration, and it can be controlled on demand by employing a synthetic gauge field, which can enable efficient switching between the ODM-unbreaking and ODM-breaking regimes. We find that the tripartite optomechanical entanglement is largely suppressed in the ODM-unbreaking regime, but it is significantly enhanced in the ODM-breaking regime. In particular, the noise robustness of quantum entanglement in the ODM-breaking regime can be more than twice than that in the ODM-unbreaking regime. This study offers a method for protecting and enhancing fragile quantum resources and for constructing noise-tolerant and dark-mode-immune quantum processors and entangled networks. Close https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.033112 doi:10.1103/PhysRevResearch.4.033112 Close
14.	Deng-Gao Lai, Wei Qin, Adam Miranowicz, Franco Nori Efficient optomechanical refrigeration of two vibrations via an auxiliary feedback loop: Giant enhancement in mechanical susceptibilities and net cooling rates Phys. Rev. Research, 4 , pp. 033102, 2022. Abstract \| Links \| BibTeX @article{Lai2022b, title = {Efficient optomechanical refrigeration of two vibrations via an auxiliary feedback loop: Giant enhancement in mechanical susceptibilities and net cooling rates}, author = {Deng-Gao Lai and Wei Qin and Adam Miranowicz and Franco Nori}, url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.033102}, doi = {10.1103/PhysRevResearch.4.033102}, year = {2022}, date = {2022-08-05}, journal = {Phys. Rev. Research}, volume = {4}, pages = {033102}, abstract = {We propose a method to realize the simultaneous ground-state refrigeration of two vibrational modes beyond the resolved-sideband regime via an auxiliary feedback loop (AFL). This is realized by introducing the AFL to break the dark mode, which is formed by two vibrational modes coupled to a common cavity-field mode. We obtain analytical results of the effective mechanical susceptibilities and net-refrigeration rates, and find that in the presence of the AFL a giant enhancement can be achieved for these susceptibilities and refrigeration rates. Remarkably, the net-cooling rates under the AFL mechanism can be up to four orders of magnitude larger than those in cases without the AFL. Moreover, we show that the simultaneous ground-state refrigeration arises from the AFL mechanism, without which it vanishes. This is because in the absence of the AFL, the dark mode prevents energy extraction through the cooling channels. However, by introducing the AFL, dark-mode breaking rebuilds the refrigeration channels, and, as a result, leads to the simultaneous cooling of these vibrations. Our approach has remarkable flexibility and scalability and can be extended to the simultaneous refrigeration of a large number of vibrations beyond the resolved-sideband regime.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose a method to realize the simultaneous ground-state refrigeration of two vibrational modes beyond the resolved-sideband regime via an auxiliary feedback loop (AFL). This is realized by introducing the AFL to break the dark mode, which is formed by two vibrational modes coupled to a common cavity-field mode. We obtain analytical results of the effective mechanical susceptibilities and net-refrigeration rates, and find that in the presence of the AFL a giant enhancement can be achieved for these susceptibilities and refrigeration rates. Remarkably, the net-cooling rates under the AFL mechanism can be up to four orders of magnitude larger than those in cases without the AFL. Moreover, we show that the simultaneous ground-state refrigeration arises from the AFL mechanism, without which it vanishes. This is because in the absence of the AFL, the dark mode prevents energy extraction through the cooling channels. However, by introducing the AFL, dark-mode breaking rebuilds the refrigeration channels, and, as a result, leads to the simultaneous cooling of these vibrations. Our approach has remarkable flexibility and scalability and can be extended to the simultaneous refrigeration of a large number of vibrations beyond the resolved-sideband regime. Close https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.033102 doi:10.1103/PhysRevResearch.4.033102 Close
13.	Deng-Gao Lai, Jie-Qiao Liao, Adam Miranowicz, Franco Nori Noise-Tolerant Optomechanical Entanglement via Synthetic Magnetism Phys. Rev. Lett., 129 , pp. 063602, 2022. Abstract \| Links \| BibTeX @article{Lai2022c, title = {Noise-Tolerant Optomechanical Entanglement via Synthetic Magnetism}, author = {Deng-Gao Lai and Jie-Qiao Liao and Adam Miranowicz and Franco Nori}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.063602}, doi = {10.1103/PhysRevLett.129.063602}, year = {2022}, date = {2022-08-03}, journal = {Phys. Rev. Lett.}, volume = {129}, pages = {063602}, abstract = {Entanglement of light and multiple vibrations is a key resource for multichannel quantum information processing and memory. However, entanglement generation is generally suppressed, or even fully destroyed, by the dark-mode (DM) effect induced by the coupling of multiple degenerate or near-degenerate vibrational modes to a common optical mode. Here we propose how to generate optomechanical entanglement via DM breaking induced by synthetic magnetism. We find that at nonzero temperature, light and vibrations are separable in the DM-unbreaking regime but entangled in the DM-breaking regime. Remarkably, the threshold thermal phonon number for preserving entanglement in our simulations has been observed to be up to 3 orders of magnitude stronger than that in the DM-unbreaking regime. The application of the DM-breaking mechanism to optomechanical networks can make noise-tolerant entanglement networks feasible. These results are quite general and can initiate advances in quantum resources with immunity against both dark modes and thermal noise.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Entanglement of light and multiple vibrations is a key resource for multichannel quantum information processing and memory. However, entanglement generation is generally suppressed, or even fully destroyed, by the dark-mode (DM) effect induced by the coupling of multiple degenerate or near-degenerate vibrational modes to a common optical mode. Here we propose how to generate optomechanical entanglement via DM breaking induced by synthetic magnetism. We find that at nonzero temperature, light and vibrations are separable in the DM-unbreaking regime but entangled in the DM-breaking regime. Remarkably, the threshold thermal phonon number for preserving entanglement in our simulations has been observed to be up to 3 orders of magnitude stronger than that in the DM-unbreaking regime. The application of the DM-breaking mechanism to optomechanical networks can make noise-tolerant entanglement networks feasible. These results are quite general and can initiate advances in quantum resources with immunity against both dark modes and thermal noise. Close https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.063602 doi:10.1103/PhysRevLett.129.063602 Close
12.	Huan-Yu Ku, Josef Kadlec, Antonín Černoch, Marco Túlio Quintino, Wenbin Zhou, Karel Lemr, Neill Lambert, Adam Miranowicz, Shin-Liang Chen, Franco Nori, Yueh-Nan Chen Quantifying Quantumness of Channels Without Entanglement PRX Quantum, 3 , pp. 020338, 2022. Abstract \| Links \| BibTeX @article{Ku2022, title = {Quantifying Quantumness of Channels Without Entanglement}, author = {Huan-Yu Ku and Josef Kadlec and Antonín Černoch and Marco Túlio Quintino and Wenbin Zhou and Karel Lemr and Neill Lambert and Adam Miranowicz and Shin-Liang Chen and Franco Nori and Yueh-Nan Chen}, url = {https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.3.020338}, doi = {10.1103/PRXQuantum.3.020338}, year = {2022}, date = {2022-05-19}, journal = {PRX Quantum}, volume = {3}, pages = {020338}, abstract = {Quantum channels breaking entanglement, incompatibility, or nonlocality are defined as such because they are not useful for entanglement-based, one-sided device-independent, or device-independent quantum-information processing, respectively. Here, we show that such breaking channels are related to complementary tests of macrorealism, i.e., temporal separability, channel unsteerability, temporal unsteerability, and the temporal Bell inequality. To demonstrate this we first define a steerability-breaking channel, which is conceptually similar to entanglement and nonlocality-breaking channels and prove that it is identical to an incompatibility-breaking channel. A hierarchy of quantum nonbreaking channels is derived, akin to the existing hierarchy relations for temporal and spatial quantum correlations. We then introduce the concept of channels that break temporal correlations, explain how they are related to the standard breaking channels, and prove the following results. (1) A robustness-based measure for non-entanglement-breaking channels can be probed by temporal nonseparability. (2) A non-steerability-breaking channel can be quantified by channel steering. (3) Temporal steerability and nonmacrorealism can be used for, respectively, distinguishing unital steerability-breaking channels and nonlocality-breaking channels for a maximally entangled state. Finally, a two-dimensional depolarizing channel is experimentally implemented as a proof-of-principle example to demonstrate the hierarchy relation of nonbreaking channels using temporal quantum correlations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Quantum channels breaking entanglement, incompatibility, or nonlocality are defined as such because they are not useful for entanglement-based, one-sided device-independent, or device-independent quantum-information processing, respectively. Here, we show that such breaking channels are related to complementary tests of macrorealism, i.e., temporal separability, channel unsteerability, temporal unsteerability, and the temporal Bell inequality. To demonstrate this we first define a steerability-breaking channel, which is conceptually similar to entanglement and nonlocality-breaking channels and prove that it is identical to an incompatibility-breaking channel. A hierarchy of quantum nonbreaking channels is derived, akin to the existing hierarchy relations for temporal and spatial quantum correlations. We then introduce the concept of channels that break temporal correlations, explain how they are related to the standard breaking channels, and prove the following results. (1) A robustness-based measure for non-entanglement-breaking channels can be probed by temporal nonseparability. (2) A non-steerability-breaking channel can be quantified by channel steering. (3) Temporal steerability and nonmacrorealism can be used for, respectively, distinguishing unital steerability-breaking channels and nonlocality-breaking channels for a maximally entangled state. Finally, a two-dimensional depolarizing channel is experimentally implemented as a proof-of-principle example to demonstrate the hierarchy relation of nonbreaking channels using temporal quantum correlations. Close https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.3.020338 doi:10.1103/PRXQuantum.3.020338 Close
11.	Chia-Yi Ju, Adam Miranowicz, Fabrizio Minganti, Chuan-Tsung Chan, Guang-Yin Chen, Franco Nori Einstein's quantum elevator: Hermitization of non-Hermitian Hamiltonians via a generalized vielbein formalism Phys. Rev. Research, 4 , pp. 023070, 2022. Abstract \| Links \| BibTeX @article{Ju22prr, title = {Einstein's quantum elevator: Hermitization of non-Hermitian Hamiltonians via a generalized vielbein formalism}, author = {Chia-Yi Ju and Adam Miranowicz and Fabrizio Minganti and Chuan-Tsung Chan and Guang-Yin Chen and Franco Nori}, url = {https://link.aps.org/doi/10.1103/PhysRevResearch.4.023070}, doi = {10.1103/PhysRevResearch.4.023070}, year = {2022}, date = {2022-04-01}, journal = {Phys. Rev. Research}, volume = {4}, pages = {023070}, publisher = {American Physical Society}, abstract = {The formalism for non-Hermitian quantum systems sometimes blurs the underlying physics. We present a systematic study of the vielbeinlike formalism which transforms the Hilbert space bundles of non-Hermitian systems into the conventional ones, rendering the induced Hamiltonian to be Hermitian. In other words, any non-Hermitian Hamiltonian can be “transformed” into a Hermitian one without altering the physics. Thus we show how to find a reference frame (corresponding to Einstein's quantum elevator) in which a non-Hermitian system, equipped with a nontrivial Hilbert space metric, reduces to a Hermitian system within the standard formalism of quantum mechanics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close The formalism for non-Hermitian quantum systems sometimes blurs the underlying physics. We present a systematic study of the vielbeinlike formalism which transforms the Hilbert space bundles of non-Hermitian systems into the conventional ones, rendering the induced Hamiltonian to be Hermitian. In other words, any non-Hermitian Hamiltonian can be “transformed” into a Hermitian one without altering the physics. Thus we show how to find a reference frame (corresponding to Einstein's quantum elevator) in which a non-Hermitian system, equipped with a nontrivial Hilbert space metric, reduces to a Hermitian system within the standard formalism of quantum mechanics. Close https://link.aps.org/doi/10.1103/PhysRevResearch.4.023070 doi:10.1103/PhysRevResearch.4.023070 Close
10.	Yi-Hao Kang, Ye-Hong Chen, Xin Wang, Jie Song, Yan Xia, Adam Miranowicz, Shi-Biao Zheng, Franco Nori Nonadiabatic geometric quantum computation with cat-state qubits via invariant-based reverse engineering Phys. Rev. Research, 4 , pp. 013233, 2022. Abstract \| Links \| BibTeX @article{Kang2022, title = {Nonadiabatic geometric quantum computation with cat-state qubits via invariant-based reverse engineering}, author = {Yi-Hao Kang and Ye-Hong Chen and Xin Wang and Jie Song and Yan Xia and Adam Miranowicz and Shi-Biao Zheng and Franco Nori}, url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.013233}, doi = {10.1103/PhysRevResearch.4.013233}, year = {2022}, date = {2022-03-28}, journal = {Phys. Rev. Research}, volume = {4}, pages = {013233}, abstract = {We propose a protocol to realize nonadiabatic geometric quantum computation of small-amplitude Schrödinger cat qubits via invariant-based reverse engineering. We consider a system with a two-photon driven Kerr nonlinearity, which can generate a pair of dressed even and odd coherent states (i.e., Schrödinger cat states) for fault-tolerant quantum computations. An additional coherent field is applied to linearly drive a cavity mode, to induce oscillations between dressed cat states. By designing this linear drive with invariant-based reverse engineering, we show how to implement nonadiabatic geometric quantum computation with cat qubits. The performance of the protocol is estimated by taking into account the influence of systematic errors, additive white Gaussian noise, 1/f noise, and decoherence including photon loss and dephasing. Numerical results demonstrate that our protocol is robust against these negative factors. Therefore, this protocol may provide a feasible method for nonadiabatic geometric quantum computation in bosonic systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose a protocol to realize nonadiabatic geometric quantum computation of small-amplitude Schrödinger cat qubits via invariant-based reverse engineering. We consider a system with a two-photon driven Kerr nonlinearity, which can generate a pair of dressed even and odd coherent states (i.e., Schrödinger cat states) for fault-tolerant quantum computations. An additional coherent field is applied to linearly drive a cavity mode, to induce oscillations between dressed cat states. By designing this linear drive with invariant-based reverse engineering, we show how to implement nonadiabatic geometric quantum computation with cat qubits. The performance of the protocol is estimated by taking into account the influence of systematic errors, additive white Gaussian noise, 1/f noise, and decoherence including photon loss and dephasing. Numerical results demonstrate that our protocol is robust against these negative factors. Therefore, this protocol may provide a feasible method for nonadiabatic geometric quantum computation in bosonic systems. Close https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.013233 doi:10.1103/PhysRevResearch.4.013233 Close
2021
9.	Fabrizio Minganti, Ievgen I Arkhipov, Adam Miranowicz, Franco Nori Continuous dissipative phase transitions with or without symmetry breaking New Journal of Physics, 23 (12), pp. 122001, 2021. Abstract \| Links \| BibTeX @article{Minganti2021b, title = {Continuous dissipative phase transitions with or without symmetry breaking}, author = {Fabrizio Minganti and Ievgen I Arkhipov and Adam Miranowicz and Franco Nori}, url = {https://doi.org/10.1088/1367-2630/ac3db8}, doi = {10.1088/1367-2630/ac3db8}, year = {2021}, date = {2021-12-22}, journal = {New Journal of Physics}, volume = {23}, number = {12}, pages = {122001}, publisher = {IOP Publishing}, abstract = {The paradigm of second-order phase transitions (PTs) induced by spontaneous symmetry breaking (SSB) in thermal and quantum systems is a pillar of modern physics that has been fruitfully applied to out-of-equilibrium open quantum systems. Dissipative phase transitions (DPTs) of second order are often connected with SSB, in close analogy with well-known thermal second-order PTs in closed quantum and classical systems. That is, a second-order DPT should disappear by preventing the occurrence of SSB. Here, we prove this statement to be wrong, showing that, surprisingly, SSB is not a necessary condition for the occurrence of second-order DPTs in out-of-equilibrium open quantum systems. We analytically prove this result using the Liouvillian theory of DPTs, and demonstrate this anomalous transition in a paradigmatic laser model, where we can arbitrarily remove SSB while retaining criticality, and on a Z2-symmetric model of a two-photon Kerr resonator. This new type of PT cannot be interpreted as a ‘semiclassical’ bifurcation, because, after the DPT, the system steady state remains unique.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close The paradigm of second-order phase transitions (PTs) induced by spontaneous symmetry breaking (SSB) in thermal and quantum systems is a pillar of modern physics that has been fruitfully applied to out-of-equilibrium open quantum systems. Dissipative phase transitions (DPTs) of second order are often connected with SSB, in close analogy with well-known thermal second-order PTs in closed quantum and classical systems. That is, a second-order DPT should disappear by preventing the occurrence of SSB. Here, we prove this statement to be wrong, showing that, surprisingly, SSB is not a necessary condition for the occurrence of second-order DPTs in out-of-equilibrium open quantum systems. We analytically prove this result using the Liouvillian theory of DPTs, and demonstrate this anomalous transition in a paradigmatic laser model, where we can arbitrarily remove SSB while retaining criticality, and on a Z2-symmetric model of a two-photon Kerr resonator. This new type of PT cannot be interpreted as a ‘semiclassical’ bifurcation, because, after the DPT, the system steady state remains unique. Close https://doi.org/10.1088/1367-2630/ac3db8 doi:10.1088/1367-2630/ac3db8 Close
8.	Fabrizio Minganti, Ievgen I Arkhipov, Adam Miranowicz, Franco Nori Liouvillian spectral collapse in the Scully-Lamb laser model Physical Review Research, 3 (4), pp. 043197, 2021. Abstract \| Links \| BibTeX @article{Minganti2021, title = {Liouvillian spectral collapse in the Scully-Lamb laser model}, author = {Fabrizio Minganti and Ievgen I Arkhipov and Adam Miranowicz and Franco Nori}, url = {https://doi.org/10.1103/physrevresearch.3.043197}, doi = {10.1103/physrevresearch.3.043197}, year = {2021}, date = {2021-12-21}, journal = {Physical Review Research}, volume = {3}, number = {4}, pages = {043197}, publisher = {American Physical Society (APS)}, abstract = {Phase transitions of thermal systems and the laser threshold were first connected more than forty years ago. Despite the nonequilibrium nature of the laser, the Landau theory of thermal phase transitions, applied directly to the Scully-Lamb laser model (SLLM), indicates that the laser threshold is a second-order phase transition, associated with a U(1) spontaneous symmetry breaking (SSB). To capture the genuine nonequilibrium phase transition of the SLLM (i.e., a single-mode laser without a saturable absorber), here we employ a quantum theory of dissipative phase transitions. Our results confirm that the U(1) SSB can occur at the lasing threshold but, in contrast to the Landau theory and semiclassical approximation, they signal that the SLLM “fundamental” transition is a different phenomenon, which we call Liouvillian spectral collapse; that is, the emergence of diabolic points of infinite degeneracy. By considering a generalized SLLM with additional dephasing, we witness a second-order phase transition, with a Liouvillian spectral collapse, but in the absence of symmetry breaking. Most surprisingly, the phase transition corresponds to the emergence of dynamical multistability even without SSB. Normally, bistability is suppressed by quantum fluctuations, while in this case, the very presence of quantum fluctuations enables bistability. This rather anomalous bistability, characterizing the truly dissipative and quantum origin of lasing, can be an experimental signature of our predictions, and we show that it is associated with an emergent dynamical hysteresis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Phase transitions of thermal systems and the laser threshold were first connected more than forty years ago. Despite the nonequilibrium nature of the laser, the Landau theory of thermal phase transitions, applied directly to the Scully-Lamb laser model (SLLM), indicates that the laser threshold is a second-order phase transition, associated with a U(1) spontaneous symmetry breaking (SSB). To capture the genuine nonequilibrium phase transition of the SLLM (i.e., a single-mode laser without a saturable absorber), here we employ a quantum theory of dissipative phase transitions. Our results confirm that the U(1) SSB can occur at the lasing threshold but, in contrast to the Landau theory and semiclassical approximation, they signal that the SLLM “fundamental” transition is a different phenomenon, which we call Liouvillian spectral collapse; that is, the emergence of diabolic points of infinite degeneracy. By considering a generalized SLLM with additional dephasing, we witness a second-order phase transition, with a Liouvillian spectral collapse, but in the absence of symmetry breaking. Most surprisingly, the phase transition corresponds to the emergence of dynamical multistability even without SSB. Normally, bistability is suppressed by quantum fluctuations, while in this case, the very presence of quantum fluctuations enables bistability. This rather anomalous bistability, characterizing the truly dissipative and quantum origin of lasing, can be an experimental signature of our predictions, and we show that it is associated with an emergent dynamical hysteresis. Close https://doi.org/10.1103/physrevresearch.3.043197 doi:10.1103/physrevresearch.3.043197 Close
7.	Kateřina Jirákov á, Antonín Č, Karel Lemr, Karol Bartkiewicz, Adam Miranowicz Experimental hierarchy and optimal robustness of quantum correlations of two-qubit states with controllable white noise Physical Review A, 104 (6), pp. 062436, 2021. Abstract \| Links \| BibTeX @article{Jirakova2021b, title = {Experimental hierarchy and optimal robustness of quantum correlations of two-qubit states with controllable white noise}, author = {Kate{ř}ina Jirákov á and Antonín Č and Karel Lemr and Karol Bartkiewicz and Adam Miranowicz}, url = {https://doi.org/10.1103/physreva.104.062436}, doi = {10.1103/physreva.104.062436}, year = {2021}, date = {2021-12-21}, journal = {Physical Review A}, volume = {104}, number = {6}, pages = {062436}, publisher = {American Physical Society (APS)}, abstract = {We demonstrate a hierarchy of various classes of quantum correlations on experimentally prepared two-qubit Werner-like states with controllable white noise. Werner states, which are white-noise-affected Bell states, are prototypal examples for studying such a hierarchy as a function of the amount of white noise. We experimentally generate Werner states and their generalizations, i.e., partially entangled pure states affected by white noise. These states enable us to study the hierarchy of the following classes of correlations: separability, entanglement, steering in three- and two-measurement scenarios, and Bell nonlocality. We show that the generalized Werner states (GWSs) reveal fundamentally different aspects of the hierarchy compared to the Werner states. In particular, we find five different parameter regimes of the GWSs, including those steerable in a two-measurement scenario but not violating Bell inequalities. This regime cannot be observed for the usual Werner states. Moreover, we find threshold curves separating different regimes of the quantum correlations and find the optimal states which allow for the largest amount of white noise which does not destroy their specific quantum correlations (e.g., unsteerable entanglement). Thus, we could identify the optimal Bell-nondiagonal GWSs which are, for this specific meaning, more robust against the white noise compared to the Bell-diagonal GWSs (i.e., Werner states).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We demonstrate a hierarchy of various classes of quantum correlations on experimentally prepared two-qubit Werner-like states with controllable white noise. Werner states, which are white-noise-affected Bell states, are prototypal examples for studying such a hierarchy as a function of the amount of white noise. We experimentally generate Werner states and their generalizations, i.e., partially entangled pure states affected by white noise. These states enable us to study the hierarchy of the following classes of correlations: separability, entanglement, steering in three- and two-measurement scenarios, and Bell nonlocality. We show that the generalized Werner states (GWSs) reveal fundamentally different aspects of the hierarchy compared to the Werner states. In particular, we find five different parameter regimes of the GWSs, including those steerable in a two-measurement scenario but not violating Bell inequalities. This regime cannot be observed for the usual Werner states. Moreover, we find threshold curves separating different regimes of the quantum correlations and find the optimal states which allow for the largest amount of white noise which does not destroy their specific quantum correlations (e.g., unsteerable entanglement). Thus, we could identify the optimal Bell-nondiagonal GWSs which are, for this specific meaning, more robust against the white noise compared to the Bell-diagonal GWSs (i.e., Werner states). Close https://doi.org/10.1103/physreva.104.062436 doi:10.1103/physreva.104.062436 Close
6.	Hai Xu, Deng-Gao Lai, Yi-Bing Qian, Bang-Pin Hou, Adam Miranowicz, Franco Nori Optomechanical dynamics in the PT- and broken-PT-symmetric regimes Physical Review A, 104 (5), pp. 053518, 2021. Abstract \| Links \| BibTeX @article{Xu2021, title = {Optomechanical dynamics in the PT- and broken-PT-symmetric regimes}, author = {Hai Xu and Deng-Gao Lai and Yi-Bing Qian and Bang-Pin Hou and Adam Miranowicz and Franco Nori}, url = {https://doi.org/10.1103/physreva.104.053518}, doi = {10.1103/physreva.104.053518}, year = {2021}, date = {2021-11-04}, journal = {Physical Review A}, volume = {104}, number = {5}, pages = {053518}, publisher = {American Physical Society (APS)}, abstract = {We theoretically study the dynamics of an optomechanical system, consisting of a passive optical mode and an active mechanical mode, in the PT- and broken-PT-symmetric regimes. By fully analytical treatments for the dynamics of the average displacement and particle numbers, we reveal the phase diagram under different conditions and the various regimes of both PT symmetry and stability of the system. We find that by appropriately tuning either mechanical gain or optomechanical coupling, both phase transitions of the PT symmetry and stability of the system can be flexibly controlled. As a result, the dynamical behaviors of the average displacement, photons, and phonons are radically changed in different regimes. The presented physical mechanism is general and this method can be extended to a general model of dissipative and amplified coupled systems. Our study shows that PT-symmetric optomechanical devices can serve as a powerful tool for the manipulation of mechanical motion, photons, and phonons.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We theoretically study the dynamics of an optomechanical system, consisting of a passive optical mode and an active mechanical mode, in the PT- and broken-PT-symmetric regimes. By fully analytical treatments for the dynamics of the average displacement and particle numbers, we reveal the phase diagram under different conditions and the various regimes of both PT symmetry and stability of the system. We find that by appropriately tuning either mechanical gain or optomechanical coupling, both phase transitions of the PT symmetry and stability of the system can be flexibly controlled. As a result, the dynamical behaviors of the average displacement, photons, and phonons are radically changed in different regimes. The presented physical mechanism is general and this method can be extended to a general model of dissipative and amplified coupled systems. Our study shows that PT-symmetric optomechanical devices can serve as a powerful tool for the manipulation of mechanical motion, photons, and phonons. Close https://doi.org/10.1103/physreva.104.053518 doi:10.1103/physreva.104.053518 Close
5.	Ying Li, Ya-Feng Jiao, Jing-Xue Liu, Adam Miranowicz, Yun-Lan Zuo, Le-Man Kuang, Hui Jing Vector optomechanical entanglement Nanophotonics, 11 (1), pp. 67–77, 2021. Abstract \| Links \| BibTeX @article{Li2021, title = {Vector optomechanical entanglement}, author = {Ying Li and Ya-Feng Jiao and Jing-Xue Liu and Adam Miranowicz and Yun-Lan Zuo and Le-Man Kuang and Hui Jing}, url = {https://doi.org/10.1515/nanoph-2021-0485}, doi = {10.1515/nanoph-2021-0485}, year = {2021}, date = {2021-11-02}, journal = {Nanophotonics}, volume = {11}, number = {1}, pages = {67--77}, abstract = {The polarizations of optical fields, besides field intensities, provide more degrees of freedom to manipulate coherent light–matter interactions. Here, we propose how to achieve a coherent switch of optomechanical entanglement in a polarized-light-driven cavity system. We show that by tuning the polarizations of the driving field, the effective optomechanical coupling can be well controlled and, as a result, quantum entanglement between the mechanical oscillator and the optical transverse electric mode can be coherently and reversibly switched to that between the same phonon mode and the optical transverse magnetic mode. This ability to switch optomechanical entanglement with such a vectorial device can be important for building a quantum network being capable of efficient quantum information interchanges between processing nodes and flying photons.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close The polarizations of optical fields, besides field intensities, provide more degrees of freedom to manipulate coherent light–matter interactions. Here, we propose how to achieve a coherent switch of optomechanical entanglement in a polarized-light-driven cavity system. We show that by tuning the polarizations of the driving field, the effective optomechanical coupling can be well controlled and, as a result, quantum entanglement between the mechanical oscillator and the optical transverse electric mode can be coherently and reversibly switched to that between the same phonon mode and the optical transverse magnetic mode. This ability to switch optomechanical entanglement with such a vectorial device can be important for building a quantum network being capable of efficient quantum information interchanges between processing nodes and flying photons. Close https://doi.org/10.1515/nanoph-2021-0485 doi:10.1515/nanoph-2021-0485 Close
4.	Deng-Gao Lai, Wei Qin, Bang-Pin Hou, Adam Miranowicz, Franco Nori Significant enhancement in refrigeration and entanglement in auxiliary-cavity-assisted optomechanical systems Phys. Rev. A, 104 , pp. 043521, 2021. Abstract \| Links \| BibTeX @article{Lai2021, title = {Significant enhancement in refrigeration and entanglement in auxiliary-cavity-assisted optomechanical systems}, author = {Deng-Gao Lai and Wei Qin and Bang-Pin Hou and Adam Miranowicz and Franco Nori}, url = {https://journals.aps.org/pra/abstract/10.1103/PhysRevA.104.043521}, doi = {10.1103/PhysRevA.104.043521}, year = {2021}, date = {2021-10-22}, journal = {Phys. Rev. A}, volume = {104}, pages = {043521}, abstract = {We propose how to achieve significantly enhanced quantum refrigeration and entanglement by coupling a pumped auxiliary cavity to an optomechanical cavity. We obtain both analytical and numerical results and find optimal-refrigeration and -entanglement conditions under the auxiliary-cavity-assisted (ACA) mechanism. Our method leads to a significant amplification in the net refrigeration rate and reveals that the ACA entanglement has a much stronger noise robustness in comparison with the unassisted case. By appropriately designing the ACA mechanism, an effective mechanical susceptibility can be well adjusted, and a genuine tripartite entanglement of cooling-cavity photons, auxiliary-cavity photons, and phonons can be generated. Specifically, we show that both optomechanical refrigeration and entanglement can be greatly enhanced for the blue-detuned driving of the auxiliary cavity but suppressed for the red-detuned case. Our work paves a way towards further quantum control of macroscopic mechanical systems and the enhancement and protection of fragile quantum resources.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose how to achieve significantly enhanced quantum refrigeration and entanglement by coupling a pumped auxiliary cavity to an optomechanical cavity. We obtain both analytical and numerical results and find optimal-refrigeration and -entanglement conditions under the auxiliary-cavity-assisted (ACA) mechanism. Our method leads to a significant amplification in the net refrigeration rate and reveals that the ACA entanglement has a much stronger noise robustness in comparison with the unassisted case. By appropriately designing the ACA mechanism, an effective mechanical susceptibility can be well adjusted, and a genuine tripartite entanglement of cooling-cavity photons, auxiliary-cavity photons, and phonons can be generated. Specifically, we show that both optomechanical refrigeration and entanglement can be greatly enhanced for the blue-detuned driving of the auxiliary cavity but suppressed for the red-detuned case. Our work paves a way towards further quantum control of macroscopic mechanical systems and the enhancement and protection of fragile quantum resources. Close https://journals.aps.org/pra/abstract/10.1103/PhysRevA.104.043521 doi:10.1103/PhysRevA.104.043521 Close
3.	Wei Qin, Adam Miranowicz, Hui Jing, Franco Nori Generating Long-Lived Macroscopically Distinct Superposition States in Atomic Ensembles Phys. Rev. Lett., 127 , pp. 093602, 2021. Abstract \| Links \| BibTeX @article{Qin2021, title = {Generating Long-Lived Macroscopically Distinct Superposition States in Atomic Ensembles}, author = {Wei Qin and Adam Miranowicz and Hui Jing and Franco Nori}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.093602}, doi = {10.1103/PhysRevLett.127.093602}, year = {2021}, date = {2021-08-23}, journal = {Phys. Rev. Lett.}, volume = {127}, pages = {093602}, abstract = {We propose to create and stabilize long-lived macroscopic quantum superposition states in atomic ensembles. We show that using a fully quantum parametric amplifier can cause the simultaneous decay of two atoms and, in turn, create stabilized atomic Schrödinger cat states. Remarkably, even with modest parameters these intracavity atomic cat states can have an extremely long lifetime, up to 4 orders of magnitude longer than that of intracavity photonic cat states under the same parameter conditions, reaching tens of milliseconds. This lifetime of atomic cat states is ultimately limited to several seconds by extremely weak spin relaxation and thermal noise. Our work opens up a new way toward the long-standing goal of generating large-size and long-lived cat states, with immediate interests both in fundamental studies and noise-immune quantum technologies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose to create and stabilize long-lived macroscopic quantum superposition states in atomic ensembles. We show that using a fully quantum parametric amplifier can cause the simultaneous decay of two atoms and, in turn, create stabilized atomic Schrödinger cat states. Remarkably, even with modest parameters these intracavity atomic cat states can have an extremely long lifetime, up to 4 orders of magnitude longer than that of intracavity photonic cat states under the same parameter conditions, reaching tens of milliseconds. This lifetime of atomic cat states is ultimately limited to several seconds by extremely weak spin relaxation and thermal noise. Our work opens up a new way toward the long-standing goal of generating large-size and long-lived cat states, with immediate interests both in fundamental studies and noise-immune quantum technologies. Close https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.093602 doi:10.1103/PhysRevLett.127.093602 Close
2.	Ievgen I Arkhipov, Fabrizio Minganti, Adam Miranowicz, Franco Nori Generating high-order quantum exceptional points in synthetic dimensions Physical Review A, 104 (1), pp. 012205, 2021. Abstract \| Links \| BibTeX @article{Arkhipov2021b, title = {Generating high-order quantum exceptional points in synthetic dimensions}, author = {Ievgen I Arkhipov and Fabrizio Minganti and Adam Miranowicz and Franco Nori}, url = {https://doi.org/10.1103/physreva.104.012205}, doi = {10.1103/physreva.104.012205}, year = {2021}, date = {2021-07-08}, journal = {Physical Review A}, volume = {104}, number = {1}, pages = {012205}, publisher = {American Physical Society (APS)}, abstract = {Recently, there has been intense research in proposing and developing various methods for constructing high-order exceptional points (EPs) in dissipative systems. These EPs can possess a number of intriguing properties related to, e.g., chiral transport and enhanced sensitivity. Previous proposals to realize non-Hermitian Hamiltonians (NHHs) with high-order EPs have been mainly based on either direct construction of spatial networks of coupled modes or utilization of synthetic dimensions, e.g., mapping of spatial lattices to time or photon-number space. Both methods rely on the construction of effective NHHs describing classical or postselected quantum fields, which neglect the effects of quantum jumps and which, thus, suffer from a scalability problem in the quantum regime, when the probability of quantum jumps increases with the number of excitations and dissipation rate. Here, by considering the full quantum dynamics of a quadratic Liouvillian superoperator, we introduce a simple and effective method for engineering NHHs with high-order quantum EPs, derived from evolution matrices of system operator moments. That is, by quantizing higher-order moments of system operators, e.g., of a quadratic two-mode system, the resulting evolution matrices can be interpreted as alternative NHHs describing, e.g., a spatial lattice of coupled resonators, where spatial sites are represented by high-order field moments in the synthetic space of field moments. Notably, such a mapping allows correct reproduction of the results of the Liouvillian dynamics, including quantum jumps. As an example, we consider a U(1)-symmetric quadratic Liouvillian describing a bimodal cavity with incoherent mode coupling, which can also possess anti−PT symmetry, whose field moment dynamics can be mapped to an NHH governing a spatial network of coupled resonators with high-order EPs.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Recently, there has been intense research in proposing and developing various methods for constructing high-order exceptional points (EPs) in dissipative systems. These EPs can possess a number of intriguing properties related to, e.g., chiral transport and enhanced sensitivity. Previous proposals to realize non-Hermitian Hamiltonians (NHHs) with high-order EPs have been mainly based on either direct construction of spatial networks of coupled modes or utilization of synthetic dimensions, e.g., mapping of spatial lattices to time or photon-number space. Both methods rely on the construction of effective NHHs describing classical or postselected quantum fields, which neglect the effects of quantum jumps and which, thus, suffer from a scalability problem in the quantum regime, when the probability of quantum jumps increases with the number of excitations and dissipation rate. Here, by considering the full quantum dynamics of a quadratic Liouvillian superoperator, we introduce a simple and effective method for engineering NHHs with high-order quantum EPs, derived from evolution matrices of system operator moments. That is, by quantizing higher-order moments of system operators, e.g., of a quadratic two-mode system, the resulting evolution matrices can be interpreted as alternative NHHs describing, e.g., a spatial lattice of coupled resonators, where spatial sites are represented by high-order field moments in the synthetic space of field moments. Notably, such a mapping allows correct reproduction of the results of the Liouvillian dynamics, including quantum jumps. As an example, we consider a U(1)-symmetric quadratic Liouvillian describing a bimodal cavity with incoherent mode coupling, which can also possess anti−PT symmetry, whose field moment dynamics can be mapped to an NHH governing a spatial network of coupled resonators with high-order EPs. Close https://doi.org/10.1103/physreva.104.012205 doi:10.1103/physreva.104.012205 Close
1.	Ye-Hong Chen, Wei Qin, Xin Wang, Adam Miranowicz, Franco Nori Shortcuts to Adiabaticity for the Quantum Rabi Model: Efficient Generation of Giant Entangled Cat States via Parametric Amplification Phys. Rev. Lett., 126 , pp. 023602, 2021. Abstract \| Links \| BibTeX @article{PhysRevLett.126.023602, title = {Shortcuts to Adiabaticity for the Quantum Rabi Model: Efficient Generation of Giant Entangled Cat States via Parametric Amplification}, author = {Ye-Hong Chen and Wei Qin and Xin Wang and Adam Miranowicz and Franco Nori}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.126.023602}, doi = {10.1103/PhysRevLett.126.023602}, year = {2021}, date = {2021-01-14}, journal = {Phys. Rev. Lett.}, volume = {126}, pages = {023602}, publisher = {American Physical Society}, abstract = {We propose a method for the fast generation of nonclassical ground states of the Rabi model in the ultrastrong and deep-strong coupling regimes via the shortcuts-to-adiabatic (STA) dynamics. The time-dependent quantum Rabi model is simulated by applying parametric amplification to the Jaynes-Cummings model. Using experimentally feasible parametric drive, this STA protocol can generate large-size Schrödinger cat states, through a process that is ∼10 times faster compared to adiabatic protocols. Such fast evolution increases the robustness of our protocol against dissipation. Our method enables one to freely design the parametric drive, so that the target state can be generated in the lab frame. A largely detuned light-matter coupling makes the protocol robust against imperfections of the operation times in experiments.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We propose a method for the fast generation of nonclassical ground states of the Rabi model in the ultrastrong and deep-strong coupling regimes via the shortcuts-to-adiabatic (STA) dynamics. The time-dependent quantum Rabi model is simulated by applying parametric amplification to the Jaynes-Cummings model. Using experimentally feasible parametric drive, this STA protocol can generate large-size Schrödinger cat states, through a process that is ∼10 times faster compared to adiabatic protocols. Such fast evolution increases the robustness of our protocol against dissipation. Our method enables one to freely design the parametric drive, so that the target state can be generated in the lab frame. A largely detuned light-matter coupling makes the protocol robust against imperfections of the operation times in experiments. Close https://link.aps.org/doi/10.1103/PhysRevLett.126.023602 doi:10.1103/PhysRevLett.126.023602 Close