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Shang-Bin Li

Publications and source records attributed to Shang-Bin Li.

At least 19 recordsLinked to original sources

Signature candidate of quantum chaos far from the semiclassical regime

We numerically investigated the entanglement product in the simplest coupled kicked top model with the spin $j=1$. Different from the dynamical pattern of entanglement in the semiclassical regime, two similar initial states may have discordant entanglement oscillations. A candidate of the quantum signature of this classical chaotic system was proposed. The potential antimonotonic relation between the rank correlation coefficient qualifying the concordant of two entanglement evolutions and the stationary entanglement was preliminarily revealed.

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Competition of different evaluation schemes in the continuous variable game

An asymmetric generalization of classical Cournot's duopoly game was introduced and the simulation scheme of its quantized version was analyzed. In this scheme, the player assigned by a 'classical' measurement scheme always wins the player assigned by a quantum measurement scheme. It was shown that the fluctuation causes the disadvantage game rule of the 'quantum' player.

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Simulation of continuous variable quantum games without entanglement

A simulation scheme of quantum version of Cournot's Duopoly is proposed, in which there is a new Nash equilibrium that may be also Pareto optimal without any entanglement involved. The unique property of this simulation scheme is decoherence-free against the symmetric photon loss. Furthermore, we analyze the effects of the asymmetric information on this simulation scheme and investigate the case of asymmetric game caused by asymmetric photon loss. A second-order phase transition-like behavior of the average profits of the firm 1 and firm 2 in Nash equilibrium can be observed with the change of the degree of asymmetry of the information or the degree of "virtual cooperation". It is also found that asymmetric photon loss in this simulation scheme plays a similar role with the asymmetric entangled states in the quantum game. PACS numbers: 02.50.Le, 03.67.-a

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Mean parity of single quantum excitation of some optical fields in thermal environments

The mean parity (the Wigner function at the origin) of excited binomial states, excited coherent states and excited thermal states in thermal channel is investigated in details. It is found that the single-photon excited binomial state and the single-photon excited coherent state exhibit certain similarity in the aspect of their mean parity in the thermal channel. We show the negative mean parity can be regarded as an indicator of nonclassicality of single-photon excitation of optical fields with a little coherence, especially for the single-photon excited thermal states.

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Squeezing induced transition of long-time decay rate

We investigate the nonclassicality of several kinds of nonclassical optical fields such as the pure or mixed single photon-added coherent states and the cat states in the photon-loss or the dephasing channels by exploring the entanglement potential as the measure. It is shown that the long-time decay of entanglement potentials of these states in photon loss channel is dependent of their initial quadrature squeezing properties. In the case of photon-loss, transition of long-time decay rate emerges at the boundary between the squeezing and non-squeezing initial non-gaussian states if log-negativity is adopted as the measure of entanglement potential. However, the transition behavior disappears if the concurrence is adopted as the measure of entanglement potential. For the case of the dephasing, distinct decay behaviors of the nonclassicality are also revealed.

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Maximally entangled mixed states of two atoms trapped inside an optical cavity

In some off-resonant cases, the reduced density matrix of two atoms symmetrically coupled with an optical cavity can very approximately approach to maximally entangled mixed states or maximal Bell violation mixed states in their evolution. The influence of phase decoherence on the generation of maximally entangled mixed state is also discussed. PACS numbers: 03.67.-a, 03.65.Ud

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Stationary entanglement and nonlocality of two qubits or qutrits collectively interacting with the thermal environment: The role of Bell singlet state

We investigate the stationary entanglement and stationary nonlocality of two qubits collectively interacting with a common thermal environment. We assume two qubits are initially in Werner state or Werner-like state, and find that thermal environment can make two qubits become stationary nonlocality. The analytical relations among average thermal photon number of the environment, entanglement and nonlocality of two qubits are given in details. It is shown that the fraction of Bell singlet state plays a key role in the phenomenon that the common thermal reservoir can enhance the entanglement of two qubits. Moreover, we find that the collective decay of two qubits in a thermal reservoir at zero-temperature can generate a stationary maximally entangled mixed state if only the fraction of Bell singlet state in the initial state is not smaller than 2/3. It provides us a feasible way to prepare the maximally entangled mixed state in various physical systems such as the trapped ions, quantum dots or Josephson Junctions. For the case in which two qutrits collectively coupled with the thermal reservoir at zero-temperature, we find that the collective decay can induce the entanglement of two qutrits initially in the maximally mixed state. The collective decay of two qutrits can also induce distillable entanglement from the initial conjectured negative partial transpose bound entangled states.

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Nonclassicality of single quantum excitation of a thermal field in thermal environments

The nonclassicality of single photon-added thermal states in the thermal channel is investigated by exploring the volume of the negative part of the Wigner function. The Wigner functions become positive when the decay time exceeds a threshold value $γ{t}_c$, which only depends on the effective temperature or mean thermal photon number of the thermal channel, but not depends on the effective temperature of the initial thermal state. This phenomenon is similar with the case of single quantum excitation of classical coherent states in thermal channel. Furthermore, we firstly demonstrate $γ{t}_c$ is the same for arbitrary pure or mixed nonclassical optical fields with zero population in vacuum state. PACS numbers: 42.50.Dv, 03.65.Yz, 05.40.Ca

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Nonclassicality of quantum excitation of classical coherent fields in thermal environments

The nonclassicality of photon-added coherent fields in the thermal channel is investigated by exploring the volume of the negative part of the Wigner function which reduces with the dissipative time. The Wigner functions become positive when the decay time exceeds a threshold value. For the case of the single photon-added coherent state, we derive the exact threshold values of decay time in the thermal channel. For arbitrary partial negative Wigner distribution function, a generic analytical relation between the mean photon number of heat bath and the threshold value of decay time is presented. Finally, the possible application of SPACSs in quantum computation has been briefly discussed. OCIS codes: 270.0270, 270.2500, 000.5490

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Nonclassicality of quantum excitation of classical coherent field in photon loss channel

We investigate the nonclassicality of photon-added coherent states in the photon loss channel by exploring the entanglement potential and negative Wigner distribution. The total negative probability defined by the absolute value of the integral of the Wigner function over the negative distribution region reduces with the increase of decay time. The total negative probability and the entanglement potential of pure photon-added coherent states exhibit the similar dependence on the beam intensity. The reduce of the total negative probability is consistent with the behavior of entanglement potential for the dissipative single-photon-added coherent state at short decay times.

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Generation of maximally entangled mixed states of two atoms via on-resonance asymmetric atom-cavity couplings

A scheme for generating the maximally entangled mixed state of two atoms on-resonance asymmetrically coupled to a single mode optical cavity field is presented. The part frontier of both maximally entangled mixed states and maximal Bell violating mixed states can be approximately reached by the evolving reduced density matrix of two atoms if the ratio of coupling strengths of two atoms is appropriately controlled. It is also shown that exchange symmetry of global maximal concurrence is broken if and only if coupling strength ratio lies between $\frac{\sqrt{3}}{3}$ and $\sqrt{3}$ for the case of one-particle excitation and asymmetric coupling, while this partial symmetry-breaking can not be verified by detecting maximal Bell violation.

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Diffusion and entanglement of a kicked particle in an infinite square well under frequent measurements

We investigate the dynamics of a kicked particle in an infinite square well undergoing frequent measurements of energy. For a large class of periodic kicking force, constant diffusion is found in such a non-KAM system. The influence of phase shift of the kicking potential on the short-time dynamical behavior is discussed. The general asymptotical measurement-assisted diffusion rate is obtained. The entanglement between the particle and the measuring apparatus is investigated. There exist two distinct dynamical behaviors of entanglement. The bipartite entanglement grows with the kicking steps and it gains larger value for the more chaotic system. However, the pairwise entanglement between the system of interest and the partial spins of the measuring apparatus decreases with the kicking steps. The relation between the entanglement and quantum diffusion is also analyzed. PACS numbers: 05.45.Mt, 03.65.Ta

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Robust and fragile Werner states in the collective dephasing

We investigate the concurrence and Bell violation of the standard Werner state or Werner-like states in the presence of collective dephasing. It is shown that the standard Werner state and certain kinds of Werner-like states are robust against the collective dephasing, and some kinds of Werner-like states is fragile and becomes completely disentangled in a finite-time. The threshold time of complete disentanglement of the fragile Werner-like states is given. The influence of external driving field on the finite-time disentanglement of the standard Werner state or Werner-like states is discussed. Furthermore, we present a simple method to control the stationary state entanglement and Bell violation of two qubits. Finally, we show that the theoretical calculations of fidelity based on the initial Werner state assumption well agree with previous experimental results.

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Entanglement and quantum phase transition in quantum mixed spin chains

The ground entanglement and thermal entanglement in quantum mixed spin chains consisting of two integer spins 1 and two half integer spins 1/2 arrayed as ${1/2}-{1/2}-1-1$ in a unit cell with antiferromagnetic nearest-neighbor couplings $J_1$($J_2$) between the spins of equal (different) magnitudes, are investigated by adopting the log-negativity. The ground entanglement transition found here is closely related with the valence bond state transition, and the thermal entanglement near the critical point is calculated and shown that two distinct behaviors exist in the nearest neighbor same kind of spins and different kind of spins, respectively. The potential application of our results on the quantum information processing is also discussed.

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Entanglement of pair cat states and teleportation

The entanglement of pair cat states in the phase damping channel is studied by employing the relative entropy of entanglement. It is shown that the pair cat states can always be distillable in the phase damping channel. Furthermore, we analyze the fidelity of teleportation for the pair cat states by using joint measurements of the photon-number sum and phase difference.

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Quantum control of entanglement and information of two solid state qubits: remote control of dephasing

We investigate the scheme for controlling information characterized by Von-Neumann entropy and the stationary state entanglement characterized by concurrence of two solid state qubits in the collective dephasing channel. It is shown that the local maximal value of the stationary state concurrence always corresponds to the local minimal value of information. We also propose a scheme for remotely controlling the entanglement of two solid state qubits against the collective dephasing. This idea may open a door to remotely suppress the detrimental effects of decoherence.

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Stationary state entanglement and total correlation of two qubits or qutrits

We investigate the mutual information and entanglement of stationary state of two locally driven qubits under the influence of collective dephasing. It is shown that both the mutual information and the entanglement of two qubits in the stationary state exhibit damped oscillation with the scaled action time $γ{T}$ of the local external driving field. It means that we can control both the entanglement and total correlation of the stationary state of two qubits by adjusting the action time of the driving field. We also consider the influence of collective dephasing on entanglement of two qutrits and obtain the sufficient condition that the stationary state is entangled.

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