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Le-Man Kuang

Publications and source records attributed to Le-Man Kuang.

At least 91 records · Page 5Linked to original sources
arXiv2009

A theoretical scheme of thermal-light ghost imaging by $N$th-order intensity correlation

In this paper, we propose a theoretical scheme of ghost imaging in terms of $N$th-order correlated thermal light. We obtain the Gaussian thin lens equations in the ghost imaging protocol. We show that it is possible to produce $N-1$ ghost images of an object at different places in a nonlocal fashion by means of a higher-order correlated imaging process with an $N$th-order correlated thermal source and correlation measurement. We investigate the visibility of the ghost images in the scheme, and obtain the upper bounds of the visibility for the $N$th-order correlated thermal-light ghost imaging. It is found that the visibility of the ghost images can be dramatically enhanced when the order of correlation becomes larger.

quant-ph↗
arXiv2009

Decoherence-free quantum dynamics in circuit QED system

We study decoherence in a circuit QED system consisting of a charge qubit and two superconducting transmission line resonators (TLRs). We show that in the dispersive regime of the circuit QED system one TLR can be used as an auxiliary subsystem to realize decoherence-free quantum dynamics of the bipartite target system consisting of the charge qubit and the other TLR conditioned on the auxiliary TLR initially being a proper number state. Our study gives new insight into control and manipulation of decoherence in quantum systems.

quant-ph↗
arXiv2009

Generation of entangled coherent states for distant Bose-Einstein condensates via electromagnetically induced transparency

In this paper, we propose a method to generate entangled coherent states between two spatially separated atomic Bose-Einstein condensates (BECs) via the technique of the electromagnetically induced transparency (EIT). Two strong coupling laser beams and two entangled probe laser beams are used to make two distant BECs be in EIT states and to generate an atom-photon entangled state between probe lasers and distant BECs. The two BECs are initially in un-entangled product coherent states while the probe lasers are initially in an entangled state. Entangled states of two distant BECs can be created through performing projective measurements upon the two outgoing probe lasers under certain conditions. Concretely, we propose two protocols to show how to generate entangled coherent states of the two distant BECs. One is a single-photon scheme in which an entangled single-photon state serves the quantum channel to generate entangled distant BECs. The other is a multiphoton scheme where an entangled coherent state of the probe lasers is used as the quantum channel. Additionally, we also obtain some atom-photon entangled states of particular interest such as entangled states between a pair of optical Bell (or quasi-Bell) states and a pair of atomic entangled coherent (or quasi-Bell) states.

quant-ph↗
arXiv2009

Production of genuine entangled states of four atomic qubits

We propose an optical scheme to generate genuine entangled states of four atomic qubits in optical cavities using a single-photon source, beam splitters and single photon detectors. We show how to generate deterministically sixteen orthonormal and independent genuine entangled states of four atomic qubits. It is found that the sixteen genuine entangled states form a new type of representation of the four-atomic-qubit system, i.e., the genuine entangled-state representation. This representation brings new interesting insight onto better understanding multipartite entanglement.

quant-ph↗
arXiv2009

Transferring and bounding single photon in waveguide controlled by quantum node based on atomic ensemble

We study the scattering process of photons confined in a one dimensional optical waveguide by a laser controlled atomic ensemble. The investigation leads to an alternative setup of quantum node controlling the coherent transfer of single photon in such one dimensional continuum. To exactly solve the effective scattering equations by using the discrete coordinate approach, we simulate the linear waveguide as a coupled resonator array at the high energy limit. We generally calculate the transmission coefficients and its vanishing at resonace reflects the good controllability of our scheme. We also show that there exist two bound states to describe the localize photons around the cavity.

quant-ph↗
arXiv2009

Controlling soliton excitations in Heisenberg spin chain through magic angle

We study the nonlinear dynamics of collective excitation in a $N$-site $XXZ$ quantum spin chain, which is manipulated by an oblique magnetic field. We show that, when the tilted field is applied along the magic angle $θ_{0} =\pm\arccos \sqrt{1/3}$, the anisotropic Heisenberg spin chain becomes isotropic and thus an free propagating spin wave is stimulated. And in the regime of the tilted angle larger and smaller then the magic angle, two types of nonlinear excitations appear, which are bright soliton and dark soliton.

quant-ph↗
arXiv2008

Magneto-Optical Stern-Gerlach Effect in Atomic Ensemble

We study the birefringence of the quantized polarized light in a magneto-optically manipulated atomic ensemble as a generalized Stern-Gerlach Effect of light. To explain this engineered birefringence microscopically, we derive an effective Shrödinger equation for the spatial motion of two orthogonally polarized components, which behave as a spin with an effective magnetic moment leading to a Stern-Gerlach split in an nonuniform magnetic field. We show that electromagnetic induced transparency (EIT) mechanism can enhance the magneto-optical Stern-Gerlach effect of light in the presence of a control field with a transverse spatial profile and a inhomogeneous magnetic field.

quant-ph↗
arXiv2008

Enhanced Deflection of Light Ray by Atomic Ensemble on Coherent Population Oscillation

In recent experiments[e.g., Nature Physics 2, 332 (2006)], the enhanced light deflection in an atomic ensemble due to inhomogeneous fields is demonstrated by the electromagnetically induced transparency (EIT) based mechanism. In this paper, we explore an different mechanism for the similar phenomenon of the enhanced light deflection. This mechanism is based on the coherent population oscillation, which leads to the hole burning in the absorption spectrum. The medium causing the deflection of probe light is an ensemble of two-level atoms manipulated by a strong controlled field on the two photon resonances. In the large detuning condition, the response of the medium to the pump field and signal field is obtained with steady state approximation. And it is found that after the probe field travels across the medium, the signal ray bends due to the spatial-dependent profile of the control beam.

quant-ph↗
arXiv2008

Quantum logic gates with controllable and selective interaction for superconducting charge qubits via a nanomechanical resonator

In this paper, we propose a scheme to implement two-qubit logic gates with a controllable and selective interaction in a scalable superconducting circuit of charge qubits. A nanomechanical resonator is used as a data bus to connect qubits. It is indicated that a controllable interaction between qubits can be obtained by making use of the data bus. It is shown that a selective interaction between qubits can be realized when many qubits are involved in the system under our consideration.

quant-ph↗
arXiv2005

Implementation of non-local operations for arbitrary high-dimensional systems with qubit quantum channel

We propose a method to implement a kind of non-local operations between spatially separated two systems with arbitrary high-dimensions by using only low-dimensional qubit quantum channels and classical bit communications. The result may be generalized straightforwardly to apply for multiple systems, each of them with arbitrary dimensions. Compared with existed approaches, our method can economize classical resources and the needed low-dimensional quantum channels may be more easily established in practice. We also show the construction of the non-local quantum XOR gate for qutrit systems in terms of the obtained non-local operations as well as some single qutrit local gates.

quant-ph↗
arXiv2005

Quantum entanglement and quantum nonlocality for $N$-photon entangled states

Quantum entanglement and quantum nonlocality of $N$-photon entangled states $|ψ_{N m}> =\mathcal{N}_{m}[\cosγ|N-m>_{1}|m>_{2} +e^{iθ_{m}}\sinγ|m>_{1}|N-m>_{2}]$ and their superpositions are studied. We indicate that the relative phase $θ_{m}$ affects quantum nonlocality but not quantum entanglement for the state $|ψ_{N m}>$. We show that quantum nonlocality can be controlled and manipulated by adjusting the state parameters of $|ψ_{N m}>$, superposition coefficients, and the azimuthal angles of the Bell operator. We also show that the violation of the Bell inequality can reach its maximal value under certain conditions. It is found that quantum superpositions based on $|ψ_{N m}>$ can increase the amount of entanglement, and give more ways to reach the maximal violation of the Bell inequality.

quant-ph↗
arXiv2004

Coherent manipulation of motional states of trapped ions

The beam splitter and phase shifter, which are the key elements in the experiments of light interference, are realized in the motion of trapped ions. Some applications, such as the creation of quantum motional states and the realization of Mach-Zehnder interferometer, are illustrated. Several detection methods of motional states used in the interferometer are also discussed.

quant-ph↗
arXiv2004

Proposal for optically realizing quantum game

We present a proposal for optically implementing the quantum game of the two-player quantum prisoner's dilemma involving nonmaximally entangled states by using beam splitters, phase shifters, cross-Kerr medium, photon detector and the single-photon representation of quantum bits.

quant-ph↗
arXiv2004

Thermal entanglement in superconducting quantum-interference-device qubits coupled to cavity field

In this paper, we investigate thermal entanglement in a superconducting-quantum-interference-device qubit coupled to a cavity field. We show that the entanglement can be manipulated by varying temperature and an effective controlling parameter $B$ which depends on the external field and characteristic parameters of the system. We find that there exists a critical value of the controlling parameter $B_c$. Under a fixed temperature, increasing $B$ can increase entanglement in the regime of $B B_c$.

cond-mat.mes-hall↗
arXiv2004

Quantum dynamics of two capacitively coupled superconducting islands via Josephson junctions

In this paper, we consider a system consisting of two capacitively coupled superconducting islands via Josephson junctions. We show that it can be reduced to two coupling harmonic oscillators under certain conditions, and solved exactly in terms of a displacing transformation, a beam-splitter-like transformation, and a squeezing transformation. It is found that the system evolves by a rotated-squeezed-coherent state when the system is initially in a coherent state. Quantum dynamics of the Cooper pairs in the two superconducting islands is investigated. It is shown that the number of the Cooper pairs in the two islands evolves periodically.

cond-mat.mes-hall↗
arXiv2004

Quantum dense coding in multiparticle entangled states via local measurements

In this paper, we study quantum dense coding between two arbitrarily fixed particles in a (N+2)-particle maximally-entangled states through introducing an auxiliary qubit and carrying out local measurements. It is shown that the transmitted classical information amount through such an entangled quantum channel usually is less than two classical bits. However, the information amount may reach two classical bits of information, and the classical information capacity is independent of the number of the entangled particles in the initial entangled state under certain conditions. The results offer deeper insights to quantum dense coding via quantum channels of multi-particle entangled states.

quant-ph↗
arXiv2004

Entanglement Preserving in Quantum Copying of Three-qubit Entangled State

We study the degree to which quantum entanglement survives when a three-qubit entangled state is copied by using local and non-local processes, respectively, and investigate iterating quantum copying for the three-qubit system. There may exist inter-three-qubit entanglement and inter-two-qubit entanglement for the three-qubit system. We show that both local and non-local copying processes degrade quantum entanglement in the three-particle system due to a residual correlation between the copied output and the copying machine. We also show that the inter-two-qubit entanglement is preserved better than the inter-three-qubit entanglement in the local cloning process. We find that non-local cloning is much more efficient than the local copying for broadcasting entanglement, and output state via non-local cloning exhibits the fidelity better than local cloning.

quant-ph↗