We propose how to achieve nonreciprocal quantum entanglement of light and motion reveal its counterintuitive robustness against random losses. find that by splitting the counterpropagating lights a spinning resonator via Sagnac effect, photons phonons can be entangled strongly in chosen direction but fully uncorrelated other. This makes it possible both realize nonreciprocity even absence any classical also significant revival backscattering losses practical devices. Our work provides way...

We propose a single-photon router using single atom with an inversion center coupled to quantum multichannels made of coupled-resonator waveguides. show that the spontaneous emission can direct photons from one channel into another. The on-demand classical field perfectly switches off routing due interference in atomic amplitudes optical transitions. Total reflections incident are photonic bound state continuum. Two virtual channels, named scatter-free and controllable found, which coherent...

Intrinsic defects in optomechanical devices are generally viewed to be detrimental for achieving coherent amplification of phonons, and great care has thus been exercised fabricating materials with no (or a minimal number of) defects. Contrary this view, here we show that, by surpassing an exceptional point (EP), both the mechanical gain phonon can enhanced despite increasing defect losses. This counterintuitive effect, well described effective non-Hermitian phonon-defect model, provides...

Non-Hermitian spectral degeneracies, known as exceptional points (EPs), feature simultaneous coalescence of both eigenvalues and the associated eigenstates a system. A host intriguing EP effects their applications have been revealed in classical realm, such loss-induced lasing, single-mode laser, EP-enhanced sensing. Here we show that purely quantum effect, single-photon blockade, emerges Kerr microring resonator due to EP-induced asymmetric coupling between optical modes...

Entanglement between distant massive mechanical oscillators is of particular interest in quantum-enabled devices due to its potential applications distributed quantum information processing. Here we propose how achieve nonreciprocal remote entanglement two spatially separated within a cascaded optomechanical configuration, where the resonators are indirectly coupled through telecommunication fiber. We show that by selectively spinning resonators, one can break time-reversal symmetry this...

We propose and study an approach to realize quantum switch for single-photon transport in a coupled superconducting transmission line resonator (TLR) array with one controllable hopping interaction. find that the arbitrary wavevector can way this system. also how interaction between two TLRs via interference device (SQUID). When frequency of SQUID is largely detuned from those TLRs, variables be adiabatically eliminated thus obtained.

In this paper, we present a method to generate continuous-variable-type entangled states between photons and atoms in atomic Bose-Einstein condensate (BEC). The proposed involves an BEC with three internal states, weak quantized probe laser, strong classical coupling which form three-level $\ensuremath{\Lambda}$-shaped system. We consider situation where the is electromagnetically induced transparency laser being much stronger than laser. case, upper intermediate levels are unpopulated, so...

We propose an approach to enhance the mechanical effects of single photons in a two-mode optomechanical system. This is achieved by introducing resonance-frequency modulation cavity fields. When frequency and amplitude satisfy certain conditions, displacement induced could be larger than quantum zero-point fluctuation oscillating resonator. method can used create distinct superposition states.

We propose two alternative entanglement concentration protocols (ECPs) using the Faraday rotation of photonic polarization. Through single-photon input-output process in cavity QED, it is shown that maximally entangled atomic (photonic) state can be extracted from partially states. The distinct feature our we concentrate both and states via rotation, thus they may universal useful for experiment. Furthermore, as works low-$Q$ cavities only involves virtual excitation atoms, ECPs are...

We propose a spinning nonlinear resonator as an experimentally accessible platform to achieve nonreciprocal control of optical solitons. Nonreciprocity here results from the relativistic Sagnac-Fizeau drag effect, which is different for pump fields propagating in direction or opposite it. show that Kerr resonator, soliton states appear input directions. These solitons are more stable against losses induced by intermodal coupling between clockwise and counterclockwise modes resonator. Our...

Loss-induced transparency (LIT), featuring the revival of optical intensity by adding loss, has been demonstrated in classical optics. However, a fundamental question remained unexplored, i.e., during process LIT, whether quantum correlations photons can also be revived or even tuned increasing loss. Here we find that, accompanying LIT nonlinear optical-molecule system, purely effect as photon blockade (PB) indeed with help In particular, critical point emerges system: below point, loss...

We propose a theoretical scheme for quantum sensing of temperature close to absolute zero in quasi-one-dimensional Bose-Einstein condensate (BEC). In our scheme, single-atom impurity qubit is used as sensor. investigate the sensitivity sensor estimating BEC. demonstrate that can saturate Cram\'er-Rao bound by means measuring coherence probe qubit. study performance using signal-to-noise ratio (QSNR). It indicated there an optimal encoding time at which QSNR reach its maximum full-temperature...

Abstract Parity‐time (PT) symmetric systems with gain‐loss balanced structures can have entirely real eigenenergy spectra despite their non‐Hermitian nature, leading to peculiar discoveries such as single‐mode lasers, wireless power transfer, and non‐reciprocal light propagation. Recently, the study of PT‐symmetry has extended quantum realm, inspiring a search for PT‐symmetric effects well unique applications. Here, entanglement sensing system two qubits are studied Ising‐type interaction....

Abstract The ability to engineer entangled states that involve macroscopic objects is of particular importance for a wide variety quantum‐enabled technologies, ranging from quantum information processing sensing. Here how achieve coherent manipulation and enhancement entanglement in hybrid optomechanical system, which consists Fabry–Pérot cavity with two movable mirrors, an optical parametric amplifier (OPA), injected squeezed vacuum reservoir proposed. It shown the advantages this system...

We present a theoretical treatment of macroscopic quantum self-trapping (MQST) and coherent atomic tunneling in zero-temperature two-species Bose-Einstein condensate system the presence nonlinear self-interaction each species, interspecies interaction, Josephson-like interaction. It is shown that interactions can dramatically affect MQST tunneling, lead to collapses revivals (CR) population imbalance between two condensates. The competing effects species interaction quenching suppression CR...

We study analytically the dynamic behaviors of quantum correlation measured by discord between two uncoupled qubits, which are immersed in a common Ohmic environment. show that noninteracting qubits can be greatly amplified or protected for certain initially prepared $X$-type states time evolution. Especially, it is found there does exist stable amplification case identical and different with large detuning. It also indicated general sudden change evolution at critic point $t_c$, protection...

The cross-Kerr nonlinearity (XKNL) effect can induce efficient photon interactions in principle with which photonic multiqubit gates be performed using far fewer physical resources than linear optical schemes. Unfortunately, it is extremely challenging to generate giant nonlinearities. In recent years much effort has been made perform via weak XKNLs. However, the required strengths are still difficult achieve an experiment. We here propose XKNL-based scheme for realizing a two-photon...

Ultrastrong optomechanical interaction is a significant element for the study of fundamentals and applications physics, but its realization remains big challenge in field optomechanics. In this work, we propose reliable scheme to realize generalized ultrastrong optomechanical-like coupling cross-Kerr-type coupled two-bosonic-mode system, which one two bosonic modes strongly driven. The takes form product excitation number operator mode rotated quadrature other mode. Here, both strength phase...

We propose a reliable scheme to realize the ultrastrong Jaynes-Cummings (JC) model by simultaneously modulating resonance frequencies of two-level system and bosonic mode in quantum Rabi model. find that both high- low-frequency modulation regimes, counter-rotating terms can be completely suppressed without reducing coupling strength rotating-wave terms, hence JC Hamiltonian is achieved. The interaction not only used implement ultrafast operations such as state transfer logic gates but also...

In this paper, we investigate the effect of different optical field initial states on performance Tavis-Cummings (T-C) quantum battery. solving dynamical evolution system, found a fast way to solve Bethe ansatz equation. We find that stored energy and average charging power T-C battery are closely related probability distribution state in number states. define quantity called number-state energy. With prescribed quantity, only need know obtain at any time. propose an equal expected value...