List of publications

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}

@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}
}