@article{PhysRevB.109.L100507,
title = {Competing order in two-band Bose-Hubbard chains with extended-range interactions},
author = {Yuma Watanabe and Utso Bhattacharya and Ravindra W. Chhajlany and Javier Argüello-Luengo and Maciej Lewenstein and Tobias Graß},
url = {https://link.aps.org/doi/10.1103/PhysRevB.109.L100507},
doi = {10.1103/PhysRevB.109.L100507},
year = {2024},
date = {2024-03-01},
journal = {Phys. Rev. B},
volume = {109},
pages = {L100507},
publisher = {American Physical Society},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{PhysRevLett.131.220801,
title = {Multiparameter Estimation Perspective on Non-Hermitian Singularity-Enhanced Sensing},
author = {Javid Naikoo and Ravindra W. Chhajlany and Jan Kołodyński},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.131.220801},
doi = {10.1103/PhysRevLett.131.220801},
year = {2023},
date = {2023-11-29},
journal = {Phys. Rev. Lett.},
volume = {131},
pages = {220801},
publisher = {American Physical Society},
abstract = {Describing the evolution of quantum systems by means of non-Hermitian generators opens a new avenue to explore the dynamical properties naturally emerging in such a picture, e.g. operation at the so-called exceptional points, preservation of parity-time symmetry, or capitalizing on the singular behavior of the dynamics. In this Letter, we focus on the possibility of achieving unbounded sensitivity when using the system to sense linear perturbations away from a singular point. By combining multiparameter estimation theory of Gaussian quantum systems with the one of singular-matrix perturbations, we introduce the necessary tools to study the ultimate limits on the precision attained by such singularity-tuned sensors. We identify under what conditions and at what rate can the resulting sensitivity indeed diverge, in order to show that nuisance parameters should be generally included in the analysis, as their presence may alter the scaling of the error with the estimated parameter.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{PhysRevB.106.174503,
title = {Flat-band-induced superconductivity in synthetic bilayer optical lattices},
author = {Tymoteusz Salamon and Bernhard Irsigler and Debraj Rakshit and Maciej Lewenstein and Tobias Grass and Ravindra W. Chhajlany},
url = {https://link.aps.org/doi/10.1103/PhysRevB.106.174503},
doi = {10.1103/PhysRevB.106.174503},
year = {2022},
date = {2022-11-04},
journal = {Phys. Rev. B},
volume = {106},
pages = {174503},
publisher = {American Physical Society},
abstract = {Stacking two layers of graphene with a relative twist angle gives rise to Moiré patterns, which can strongly modify electronic behavior and may lead to unconventional superconductivity. A synthetic version of twisted bilayers can be engineered with cold atoms in optical lattices. Here, the bilayer structure is mimicked through coupling between atomic sublevels, and the twist is achieved by a spatial modulation of this coupling. In the present paper, we investigate the superconducting behavior of fermionic atoms in such a synthetic twisted bilayer lattice. Attractive interactions between the atoms are treated on the mean-field level, and the superconducting behavior is analyzed via the self-consistently determined pairing gap. A strong enhancement of the pairing gap is found when a quasi-flat band structure occurs at the Fermi surface, reflecting the prominent role played by the twist on the superconductivity. The tunability of interactions allows for the switching of superconducting correlations from intra (synthetic) layer to inter (synthetic) layer. This includes also the intermediate scenario, in which the competition between inter- and intra-layer coupling completely destroys the superconducting behavior, resulting in re-entrant superconductivity upon tuning of the interactions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@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}
}

@article{Lagoin2022,
title = {Extended Bose–Hubbard model with dipolar excitons},
author = {C. Lagoin and U. Bhattacharya and T. Grass and Ravindra W. Chhajlany and T. Salamon and K. Baldwin and L. Pfeiffer and M. Lewenstein and M. Holzmann and F. Dubin},
url = {https://www.nature.com/articles/s41586-022-05123-z},
doi = {10.1038/s41586-022-05123-z},
year = {2022},
date = {2022-09-14},
journal = {Nature},
volume = {609},
pages = {485–489},
abstract = {The Hubbard model constitutes one of the most celebrated theoretical frameworks of condensed-matter physics. It describes strongly correlated phases of interacting quantum particles confined in lattice potentials. For bosons, the Hubbard Hamiltonian has been deeply scrutinized for short-range on-site interactions. However, accessing longer-range couplings has remained elusive experimentally. This marks the frontier towards the extended Bose–Hubbard Hamiltonian, which enables insulating ordered phases at fractional lattice fillings. Here we implement this Hamiltonian by confining semiconductor dipolar excitons in an artificial two-dimensional square lattice. Strong dipolar repulsions between nearest-neighbour lattice sites then stabilize an insulating state at half filling. This characteristic feature of the extended Bose–Hubbard model exhibits the signatures theoretically expected for a chequerboard spatial order. Our work thus highlights that dipolar excitons enable controlled implementations of boson-like arrays with strong off-site interactions, in lattices with programmable geometries and more than 100 sites.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}