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Comparison between non-Markovian dynamics with and without rotating wave approximation

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Chinese Physics B 2013年第3期22卷 129-136页

作者：唐宁徐甜甜曾浩生 key laboratory of low-dimensional quantum structures and quantum control of ministry of education and Department of Physics Hunan Normal University

In the limit of weak coupling between a system and its reservoir,we derive the time-convolutionless（TCL） nonMarkovian master equation for a two-level system interacting with a zero-temperature structured environment with no rotating wave approximation（NRWA）.By comparing the dynamics with RWA,we demonstrate the impact of RWA on the system dynamics,as well as the effects of non-Markovianity on the preservation of atomic coherence,squeezing,and entanglement.

关键词： open quantum system rotating wave approximation non-Markovianity

A practical two-way system of quantum key distribution with untrusted source

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Chinese Physics B 2011年第10期20卷 40-45页

作者：陈明娟刘翔 key laboratory of low-dimensional quantum structures and quantum control of ministry of education and Department of Physics Hunan Normal University

The most severe problem of a two-way ＂plug-and-play＂（p ＆： p） quantum key distribution system is that the source can be controlled by the eavesdropper. This kind of source is defined as an ＂untrusted source＂. This paper discusses the effects of the fluctuation of internal transmittance on the final key generation rate and the transmission distance. The security of the standard BB84 protocol, one-decoy state protocol, and weak＋vacuum decoy state protocol, with untrusted sources and the fluctuation of internal transmittance are studied. It is shown that the one-decoy state is sensitive to the statistical fluctuation but weak＋vacuum decoy state is only slightly affected by the fluctuation. It is also shown that both the maximum secure transmission distance and final key generation rate are reduced when Alice＇s laboratory transmittance fluctuation is considered.

关键词： statistic fluctuation untrusted source quantum key distribution

Distribution of non-Markovian intervals for open qubit systems

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Chinese Physics B 2011年第11期20卷 47-52页

作者：郑艳萍唐宁王国友曾浩生 key laboratory of low-dimensional quantum structures and quantum control of ministry of education and Department of PhysicsHunan Normal University

We study the non-Markovianity of open qubit systems using the measure N proposed by Breuer, Laine and Piilo [Phys. Rev. Lett. 103 210401 （2009）]. We find that for the three types of quantum noises, amplitude-damping, dephasing and depolarizing noises, there exist some non-Markovian time intervals whose distribution is independent of the selection of the pair of initial states. Therefore, the maximization in the definition of measure N can be actually removed without influencing the detection of non-Markovianity.

关键词： open quantum system non-Markovianity non-Markovian interval

Chaotic matter shock wave of an open system

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Chinese Physics B 2010年第12期19卷 60-67页

作者：邓艳海文华荣识广钟宏华 Department of Physics and key laboratory of low-dimensional quantum structures and quantum control of ministry of education Hunan Normal University

We investigate a one-dimensional open Bose-Einstein condensate with attractive interaction, by considering the effect of feeding from nonequilibrium thermal cloud and applying the time-periodic inverted-harmonic potential. Using the direct perturbation method and the exact shock wave solution of the stationary Gross Pitaevskii equation, we obtain the chaotic perturbed solution and the Melnikov chaotic regions. Based on the analytical and the numerical methods, the influence of the feeding strength on the chaotic motion is revealed. It is shown that the chaotic regions could be enlarged by reducing the feeding strength and the increase of feeding strength plays a role in suppressing chaos. In the case of ＂nonpropagated＂ shock wave with fixed boundary, the number of condensed atoms increases faster as the feeding strength increases. However, for the free boundary the metastable shock wave with fixed front density oscillates its front position and atomic number aperiodically, and their amplitudes decay with the increase of the feeding strength.

关键词： Bose-Einstein condensate feeding strength shock wave chaos

Entanglement-Enhanced Two-Photon Delocalization in a Coupled-Cavity Array

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Chinese Physics Letters 2015年第4期32卷 17-20页

作者：唐世清袁季兵汪新文匡乐满 key laboratory of low-dimensional quantum structures and quantum control of ministry of education and Department of PhysicsHunan Normal University

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

关键词： TPD Entanglement-Enhanced Two-Photon Delocalization in a Coupled-Cavity Array CCA

Properties on the distant distribution of entanglement for arbitrary two-qubit pure states via noisy quantum channels

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Chinese Physics B 2009年第4期18卷 1357-1361页

作者：王琼李际新曾浩生 key laboratory of low-dimensional quantum structures and quantum control of ministry of education and Department of Physics Hunan Normal University

This paper investigates the change of entanglement for transmitting an arbitrarily entangled two-qubit pure state via one of three typical kinds of noisy quantum channels： amplitude damping quantum channel, phase damping quantum channel and depolarizing quantum channel. It finds, in all these three cases, that the output distant entanglement （measured by concurrence） reduces proportionately with respect to its initial amount, and the decaying ratio is determined only by the noisy characteristics of quantum channels and independent of the form of initial input state.

关键词： entanglement distribution quantum noisy channel concurrence

Reduction of entropic uncertainty in entangled qubits system by local PT-symmetric operation

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Chinese Physics B 2015年第9期24卷 106-110页

作者：张诗阳方卯发张延亮郭有能赵艳君唐武伟 key laboratory of low-dimensional quantum structures and quantum control of ministry of education and Department of PhysicsHunan Normal University

We investigate the quantum-memory-assisted entropic uncertainty for an entangled two-qubit system in a local quantum noise channel with PT-symmetric operation performing on one of the two particles. Our results show that the quantum-memory-assisted entropic uncertainty in the qubits system can be reduced effectively by the local PT-symmetric operation. Physical explanations for the behavior of the quantum-memory-assisted entropic uncertainty are given based on the property of entanglement of the qubits system and the non-locality induced by the re-normalization procedure for the non-Hermitian PT-symmetric operation.

关键词： entropic uncertainty relation PT-symmetric operation quantum entanglement

The squeezing dynamics of two independent atoms by detuning in two non-Markovian environments

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Chinese Physics B 2013年第12期22卷 82-86页

作者：邹红梅方卯发杨百元 key laboratory of low-dimensional quantum structures and quantum control Ministry of Education and Department of Physics Hunan Normal University

The squeezing dynamics of two independent two-level atoms off-resonantly coupled to two non-Markovian reservoirs is studied by the time-convolutionless master-equation approach. We find that the squeezing of two atoms is dependent on both detuning and the non-Markovian effect. Our results show that, in the non-Markovian regime, the bigger the detuning and the stronger the non-Markovian effect are, the larger the strength of the squeezing is. And the squeezing of two atoms can be effectively protected for a long time when both the non-Markovian effect and detuning are present simultaneously. The physical mechanism is that the detuning not only can promote the feedback of information from the environment into the atomic system but also can greatly suppress the atomic decay in the non-Markovian regime.

关键词： non-Markovian effect detuning squeezing two-level atom

Resonant frequencies of massless scalar field in rotating black-brane spacetime

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Chinese Physics B 2008年第6期17卷 1985-1989页

作者：荆继良潘启沅 key laboratory of low dimensional quantum structures and quantum control Ministry of Education Institute of Physics Hunan Normal University

This paper investigates the resonant frequencies of the massless scalar field in the near extremal Kerr-like black-brane spacetime. It is shown that the different angular quantum number will present different resonant frequencies. It is also shown that the real part of the resonant frequencies increases as the compact dimensions parameter μi increases, but the magnitude of the imaginary part decreases as μi increases.

关键词： resonant frequency black brane scalar field