arXiv subjects

Le-Man Kuang

Publications and source records attributed to Le-Man Kuang.

At least 55 records · Page 3Linked to original sources

arXiv2021

Reversible optical-microwave quantum conversion assisted by optomechanical dynamically-dark modes

We propose a dynamically-dark-mode (DDM) scheme to realize the reversible quantum conversion between microwave and optical photons in an electro-optomechanical (EOM) model. It is shown that two DDMs appear at certain times during the dynamical evolution of the EOM model. It is demonstrated that the DDMs can induce two kinds of reversible and highly efficient quantum conversion between the microwave and optical fields, the conditional quantum conversion (CQC) and the entanglement-assisted quantum conversion (EAQC). The CQC happens at the condition of vanishing of the initial-state mean value of one of the microwave and optical fields, and only depends on the coupling ratio of the system under consideration. The EAQC occurs in the presence of the initial-state entanglement between the microwave and optical fields. It is found that the EAQC can be manipulated by engineering the initial-state entanglement and the coupling ratio. It is indicated that it is possible to realize the entanglement-enhanced (or suppressed) quantum conversion through controlling the phase of the initial-state parameter. Our work highlights the power of generating reversible and highly efficient quantum conversion between microwave and optical photons by the DDMs.

quant-ph↗

arXiv2021

Nonreciprocal optical solitons in a spinning Kerr resonator

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 optical drag effect, which is different for pump fields propagating in the spinning direction or in the direction opposite to it. We show that in a spinning Kerr resonator, different soliton states appear for the input fields in different directions. These nonreciprocal solitons are more stable against losses induced by inter-modal coupling between clockwise and counterclockwise modes of the resonator. Our work builds a bridge between nonreciprocal physics and soliton science, providing a promising route towards achieving soliton-wave optical isolators and one-way soliton communications.

physics.optics↗

arXiv2020

Nonreciprocal Optomechanical Entanglement against Backscattering Losses

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

quant-ph↗

arXiv2020

Supersensitive estimation of the coupling rate in cavity optomechanics with an impurity-doped Bose-Einstein condensate

We propose a scheme to implement a supersensitive estimation of the coupling strength in a hybrid optomechanical system which consists of a cavity-Bose-Einstein condensate system coupled to an impurity. This method can dramatically improve the estimation precision even when the involved photon number is small. The quantum Fisher information indicates that the Heisenberg scale sensitivity of the coupling rate could be obtained when the photon loss rate is smaller than the corresponding critical value in the input of either coherent state or squeezed state. The critical photon decay rate for the coherent state is larger than that of the squeezed state, and the coherent state input case is more robust against the photon loss than the squeezed state case. We also present the measurement scheme which can saturate the quantum Cramér-Rao bound.

quant-ph↗

arXiv2019

Controlling quantum coherence of a two-component Bose-Einstein condensate via an impurity atom

We propose a scheme to control quantum coherence of a two-component Bose-Einstein condensate (BEC) by a single impurity atom immersed in the BEC. We show that the single impurity atom can act as a single atom valve (SAV) to control quantum coherence of the two-component BEC. It is demonstrated that the SAV can realize the on-demand control over quantum coherence at an arbitrary time. Specially, it is found that the SAV can also control higher-order quantum coherence of two-component BEC. We investigate the long-time evolution of quantum coherence of the two-component BEC. It is indicated that the single impurity atom can induce collapse and revival phenomenon of quantum coherence of the two-component BEC. Collapse-revival configurations of quantum coherence can be manipulated by the initial-state parameters of the impurity atom and the impurity-BEC interaction strengths.

cond-mat.quant-gas↗

arXiv2019

Complementarity between micro-micro and micro-macro entanglement in a Bose-Einstein condensate with two Rydberg impurities

We theoretically study complementarity between micro-micro and micro-macro entanglement in a Bose-Einstein condensate with two Rydberg impurities. We investigate quantum dynamics of micro-micro and micro-macro entanglement in the micro-macro system. It is found that strong micro-macro entanglement between Rydberg impurities and the BEC can be generated by the use of initial micro-micro entanglement between two Rydberg impurities, which acts as the seed entanglement to create micro-macro entanglement. We demonstrate a curious complementarity relation between micro-micro and micro-macro entanglement, and find that the complementarity property can be sustained to some extend even though in the presence of the BEC decoherence.

quant-ph↗

arXiv2019

Ultrastrong Jaynes-Cummings Model

We propose a reliable scheme to realize the ultrastrong Jaynes-Cummings (JC) model by simultaneously modulating the resonance frequencies of the two-level system and the bosonic mode in the ultrastrong quantum Rabi model. We find that in both the high- and low-frequency modulation regimes, the counter-rotating terms can be completely suppressed without reducing the coupling strength of the rotating-wave terms, and hence the ultrastrong JC Hamiltonian is achieved. The ultrastrong JC interaction can not only be used to implement ultrafast quantum operations, but also will open up a new route to the demonstration of quantum phase transition associated with the JC Hamiltonian across the deep-strong coupling point. Some discussions on the experimental implementation of this scheme with circuit-QED systems are presented.

quant-ph↗

arXiv2019

Mechanical engineering of photon blockades in a cavity optomechanical system

We propose to mechanically control photon blockades (PB) in an optomechanical system with driving oscillators. We show that by tuning the mechanical driving parameters we achieve selective single-photon blockade (1PB) or two-photon blockade (2PB) as well as simultaneous 1PB and 2PB at the same frequency. This mechanical engineering of 1PB and 2PB can be understood from the anharmonic energy levels due to the modulation of the mechanical driving. In contrast to the optomechanical systems without any mechanical driving featuring PB only for specific optical detuning, our results can be useful for achieving novel photon sources with multi-frequency. Our work also opens up new route to mechanically engineer quantum states exhibiting highly nonclassical photon statistics.

quant-ph↗

arXiv2018

Controlling decoherence speed limit of a single impurity atom in a Bose-Einstein-condensate reservoir

We study the decoherence speed limit (DSL) of a single impurity atom immersed in a Bose-Einsteincondensed (BEC) reservoir when the impurity atom is in a double-well potential. We demonstrate how the DSL of the impurity atom can be manipulated by engineering the BEC reservoir and the impurity potential within experimentally realistic limits. We show that the DSL can be controlled by changing key parameters such as the condensate scattering length, the effective dimension of the BEC reservoir, and the spatial configuration of the double-well potential imposed on the impurity. We uncover the physical mechanisms of controlling the DSL at root of the spectral density of the BEC reservoir.

quant-ph↗

arXiv2018

Generalized Ultrastrong Optomechanics

We propose a reliable scheme to realize a generalized ultrastrong optomechanical coupling in a two-mode cross-Kerr-type coupled system, where one of the bosonic modes is strongly driven. The effective optomechanical interaction takes the form of a product of the photon number operator of one mode and the quadrature operator of the other mode. The coupling strength and quadrature phase are both tunable via the driving field. The coupling strength can be strongly enhanced to reach the ultrastrong-coupling regime, where the few-photon optomechanical effects such as photon blockade and macroscopically distinct quantum superposition become accessible. The presence of tunable quadrature phase also enables the implementation of geometric quantum operations. Numerical simulations show that this method works well in a wide parameter space. We also present an analysis of the experimental implementation of this scheme.

quant-ph↗

arXiv2018

Near-Heisenberg-limited parameter estimation precision by a dipolar-Bose-gas reservoir engineering

We propose a scheme to obtain the Heisenberg-limited parameter estimation precision by immersing atoms in a thermally equilibrated quasi-one-dimensional dipolar Bose-Einstein condensate reservoir. We show that the collisions between the dipolar atoms and the immersed atoms can result in a controllable nonlinear interaction through tuning the relative strength and the sign of the dipolar and contact interaction. We find that the repulsive dipolar interaction reservoir is preferential for the spin squeezing and the appearance of an entangled non-Gaussian state. As a useful resource for quantum metrology, we also show that the non-Gaussian state results in the phase estimation precision in the Heisenberg scaling, outperforming that of the spin-squeezed state.

quant-ph↗

arXiv2016

Manipulating counter-rotating interactions in the quantum Rabi model via qubit frequency modulation

We propose a practical approach to manipulate the counter-rotating (CR) interactions in the quantum Rabi model by introducing a sinusoidal modulation to the transition frequency of the quantum two-level system in this model. By choosing appropriate modulation frequency and amplitude, enhancement and suppression of the CR interactions can be achieved in the Jaynes-Cummings regime (including both weak- and strong-coupling cases) as well as the ultrastrong-coupling regime. In particular, we calculate the output photon emission of the cavity vacuum state under enhanced CR terms. Our results show that continuous and steady photon emission from the cavity vacuum can be observed in the Jaynes-Cummings regime as a consequence of this enhancement. Our approach can be realized in superconducting quantum circuits.

quant-ph↗

arXiv2015

Quantum speed-up of multiqubit open system via dynamical decoupling pulses

We present a method to accelerate the dynamical evolution of multiqubit open system by employing dynamical decoupling pulses (DDPs) when the qubits are initially in W-type states. It is found that this speed-up evolution can be achieved in both of the weak-coupling regime and the strong-coupling regime. The physical mechanism behind the acceleration evolution is explained as the result of the joint action of the non-Markovianity of reservoirs and the excited-state population of qubits. It is shown that both of the non-Markovianity and the excited-state population can be controlled by DDPs to realize the quantum speed-up.

quant-ph↗

arXiv2015

Enhancement of mechanical effects of single photons in modulated two-mode optomechanics

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

quant-ph↗

arXiv2015

Manipulation of tripartite-to-bipartite entanglement localization under quantum noises and its application to entanglement distribution

This paper is to investigate the effects of quantum noises on entanglement localization by taking an example of reducing a three-qubit Greenberger-Horne-Zeilinger (GHZ) state to a two-qubit entangled state. We consider, respectively, two types of quantum decoherence, i.e., amplitude-damping and depolarizing decoherence, and explore the best von Neumann measurements on one of three qubits of the triple GHZ state for making the amount of entanglement of the collapsed bipartite state be as large as possible. The results indicate that different noises have different impacts on entanglement localization, and that the optimal strategy for reducing a three-qubit GHZ state to a two-qubit one via local measurements and classical communications in the amplitude-damping case is different from that in the noise-free case. We also show that the idea of entanglement localization could be utilized to improve the quality of bipartite entanglement distributing through amplitude-damping channels. These findings might shed a new light on entanglement manipulations and transformations.

quant-ph↗

arXiv2014

Entanglement-enhanced two-photon delocalization in a coupled-cavity array

We study transport properties of two entangled photons which are initially injected into two nearest-neighbor coupling cavities in a one-dimensional coupled-cavity array (CCA). It is found that photonic transport dynamics in the two-photon CCA exhibits entanglement-enhanced two-photon delocalization (TPD) phenomenon. It is shown that the CCA can realize the localization-to-delocalization transition for two entangled photons.

quant-ph↗

arXiv2013

Quantum-discord-induced superradiance and subradiance in a system of two separated atoms

We investigate collective radiant properties of two separated atoms in X-type quantum states. We show that quantum correlations measured by quantum discord (QD) can induce and enhance superradiance and subradiance in the two-atom system even though in the absence of interatomic quantum entanglement. We also explore quantum statistical properties of photons in the superradiance and subradiance by addressing the second-order correlation function. In particular, when the initial state of the two separated atoms is the Werner state with non-zero QD, we find that radiation photons in the superradiant region exhibit the nonclassical sub-Poissonian statistics and the degree of the sub-Poissonian statistics increases with increasing of the QD amount, while radiation photons in the subradiant region have either the sub-Poissonian or super-Poissonian statistics depending on the amount of QD and the directional angle. In the subradiant regime we predict the QD-induced photon statistics transition from the super-Poissonian to sub-Poissonian statistics. These results shed a new light on applications of QD as a quantum resource.

quant-ph↗

arXiv2013

Impurity-induced Dicke quantum phase transition in an impurity-doped cavity-Bose-Einstein condensate

We present a new generalized Dicke model, an impurity-doped Dicke model (IDDM), by the use of an impurity-doped cavity-Bose-Einstein condensate. It is shown that the impurity atom can induce Dicke quantum phase transition (QPT) from the normal phase to superradiant phase at a critic value of the impurity population. It is found that the IDDM exhibits continuous Dicke QPT with an infinite number of critical points, which is significantly different from that observed in the standard Dicke model with only one critical point. It is revealed that the impurity-induced Dicke QPT can happen in an arbitrary coupling regime of the cavity field and atoms while the Dicke QPT in the standard Dicke model occurs only in the strong coupling regime of the cavity field and atoms. This opens a way to observe the Dicke QPT in the intermediate and even weak coupling regime of the cavity field and atoms.

quant-ph↗