Quantum Decoherence of Charge Qubit Coupled to Nonlinear Nanomechanical Resonator

When the nonlinearity of nanomechanical resonator is not negligible,the quantum decoherence of charge qubit is studied analytically.Using nonlinear Jaynes–Cummings model,one explores the possibility of being quantum data bus for nonlinear nanomechanical resonator,the nonlinearity destroys the dynamical quantum information-storage and maintains the revival of quantum coherence of charge qubit.With the calculation of decoherence factor,we demonstrate the influence of the nonlinearity of nanomechanical resonator on engineered decoherence of charge qubit.     

Quantum Decoherence of Charge Qubit Coupled to Nonlinear Nanomechanical Resonator

When the nonlinearity of nanomechanical resonator is not negligible, the quantum decoherence of charge qubit is studied analytically. Using nonlinear Jaynes-Cummings model, one explores the possibility of being quantum data bus for nonlinear nanomechanical resonator, the nonlinearity destroys the dynamical quantum information-storage and maintains the revival of quantum coherence of charge qubit. With the calculation of decoherence factor, we demonstrate the influence of the nonlinearity of nanomechanical resonator on engineered decoherence of charge qubit.     

活塞驱动的指数形谐振管内的非线性振荡

本文通过理论分析和推导得到了活塞驱动的指数形谐振管内气体的压力和压比的近似表达式。对指数形谐振管的各种驱动幅值,计算了管端压比随形状参数m的变化曲线,获得最大压比时的谐振管形状参数。本文的研究结果可用于活塞驱动的指数形谐振管内非线性振荡的分析和大声幅谐振管的设计。     

Bell States and Two-Qubit Logic Gate with Superconducting Charge Qubits Coupling to a Nanomechanical Resonator

We propose a scheme for generating Bell states involving two SQUID-based charge qubits by coupling them to a nanomechanical resonator. We also show that it is possible to implement a two-qubit logic gate between the two charge qubits by choosing carefully the interaction time.     

两个正交子能级的V型三能级系统的粒子数振荡特性

研究了线偏振脉冲光场激发下,半导体量子点中两个正交子能级上的粒子数振荡特性.利用旋转波近似方法给出了共振激发和无衰减时粒子数运动方程的解析解.引入了该系统的等效跃迁偶极矩和等效脉冲面积，并给出了其关系表达式.理论分析表明，该体系中的子能级上粒子数振荡的振幅和频率都可以通过改变激发场的偏振角和系统的初态条件进行调控. 关键词： Rabi振荡 旋转波近似 三能级系统     

Quantum Thermalization and Thermal Entanglement in the Open Quantum Rabi Model

Quantum thermalization and thermal entanglement in the open quantum Rabi model (QRM), in which a two-level system and a single-mode bosonic field are coupled to either two individual heat baths or a common heat bath, are studied. By treating the QRM as an effective multilevel system and deriving global quantum master equations in the eigenstate representation of the QRM, the physical conditions for quantum thermalization of the QRM is studied. It is found that, in the individual heat-bath case, the QRM can only be thermalized when either the two heat baths have the same temperature or the QRM is only coupled to one of the two baths. In the common heat-bath case, differently, the QRM can always be thermalized. Thermal entanglement of the QRM in both the resonant- and non-resonant coupling cases is also studied. The logarithmic negativity for the thermal state of the QRM is obtained in a wide parameter space, ranging from the low- to high-temperature limits, and from the weak- to deep-strong-coupling regimes. This work paves the way toward the study of quantum effects in nonequilibrium ultrastrongly-coupled light-matter systems.     

方波电场驱动下的Rabi振荡

研究了方波电场驱动下的双Bloch带的紧束缚模型.借助Fourier分析,得到了在弱耦合极限下Rabi振荡及Rabi频率的解析解;这些结果均由电子的数值演化所证实.     

Study of Nonpolaritons in a Kerr Nonlinear Optical Resonator

We find that in a Kerr nonlinear optical resonator, the photon system possesses a new kind of quasiparticle, the nonpolariton. The existence of nonpolaritons should be testified by observing the energy density dependence of the velocity and squeezing of nonpolaritons. As we have investigated, the transition energy density of a Kerr nonlinear optical resonator is larger than that of a normal state.     

Entanglement Dynamics of Strongly-AC-Driven Superconducting Qubits in Circuit QED

We study the entanglement dynamics between two strongly-AC-driven superconducting charge qubits coupled collectively to a zero temperature, dissipative resonator and find an unusual feather that the competing of creation and annihilation of entanglement can lead to entanglement increasing, sudden death and revival. We also calculate the dependence of the death time on the initial state of the system.     

Influence of Cavity Decay on Phase Distribution and Rabi Flopping in Cavity QED

The quantum mechanical phase distribution and the quantum oscillations of population are studied for a cavity field togetherwith a driven classical field. The atom is sent through the cavity and driven by a classical field. Also the time evolution of the system including decay is obtained. The graph showing the Rabi oscillations for this system is changed into a bit pattern from the system without decay. The phase probability function is also affected due to the presence of cavity decay.     

双激子和浸润层泄漏以及俄歇俘获对量子点Rabi振荡衰减的影响

研究了脉冲激光激发下半导体量子点激子Rabi振荡中多能级过程引起的退相干特性.运用多能级粒子数运动方程组，分别计算和分析了三种多能级过程(双激子、浸润层泄漏以及俄歇俘获过程)对量子点中Rabi振荡衰减的影响.分析表明，双激子的影响在激发脉冲的脉宽较长时(>5ps)可以忽略；浸润层的泄漏虽然使得激子基态上粒子数振荡的振幅随着激发场的增强而减小，但是同时也导致了振荡平均值的减小；分析和讨论了两种俄歇俘获方式对激子振荡和复合发光的影响. 关键词： Rabi振荡 半导体量子点 退相干 俄歇俘获     

囚禁离子非线性Rabi模型量子场熵演化特性

本文研究了基于单个囚禁离子与两束激光场相互作用的非线性Rabi模型中的纠缠动力学.利用Von-Neumann熵来表征纠缠度.通过数值模拟,详细讨论了Lamb-Dicke参数对量子场熵的影响.在单光子非线性Rabi模型中,随着Lamb-Dicke参数和初始平均光子数的增加,场熵的平均值并不单调增加.在双光子非线性Rabi模型中,场熵的时间演化是周期性振荡的.随着Lamb-Dicke参数的增加,场熵的周期振荡逐渐消失.对于较小的Lamb-Dicke参数,纠缠和退纠缠周期性地出现.     

Non-Markovian Master Equation for Distant Resonators Embedded in a One-Dimensional Waveguide

We develop a master equation approach to describe the dynamics of distant resonators coupled through a one-dimensional waveguide. Our method takes into account the back-actions of the reservoirs, and enables us to calculate the exact dynamics of the complete system at all times. We show that such system can cause nonexponential and long-lived photon decay due to the existence of a relaxation effect. The physical origin of non-Markovianity in our model system is the finite propagation speed resulting in time delays in communication between the nodes, and strong decay rate of the emitters into the waveguide. When the distance satisfies the standing wave condition, we find that when the time delay is increased, the dark modes formation is no longer perfect, and the average photon number of dark mode decreases in steady time limit.     

New Criteria on Oscillatory and Asymptotic Behavior of Third-Order Nonlinear Dynamic Equations with Nonlinear Neutral Terms

In the paper, we provide sufficient conditions for the oscillatory and asymptotic behavior of a new type of third-order nonlinear dynamic equations with mixed nonlinear neutral terms. Our theorems not only improve and extend existing theorems in the literature but also provide a new approach as far as the nonlinear neutral terms are concerned. The main results are illustrated by some particular examples.     

Nonlinear Neutral Delay Differential Equations of Fourth-Order: Oscillation of Solutions

The objective of this paper is to study oscillation of fourth-order neutral differential equation. By using Riccati substitution and comparison technique, new oscillation conditions are obtained which insure that all solutions of the studied equation are oscillatory. Our results complement some known results for neutral differential equations. An illustrative example is included.     

Tunneling dynamics of a few bosons with both two-and three-body interactions in a double-well potential

We investigate the tunneling dynamics of a few bosons with both two-and three-body interactions in a doublewell potential. Uncorrelated tunneling of Rabi oscillation with the minimum period can happen only when the two-and three-body interactions satisfy a critical condition, i.e., the effective interaction energy is minimized. When the atomic interactions are slightly away from the critical condition in the weak interaction regime, the uncorrelated tunneling exhibits collapse-revival character. When the atomic interactions are strong and far away from the critical condition, the correlated tunneling with Rabi oscillation occurs. The tunneling period(the period of collapse-revival) increases(decreases) when the rate between the two-body and three-body interactions is away from the corresponding critical condition or when the number of bosons increases. Further, the tunneling properties are understood with the help of the energy spectrum of the system. Eventually, the effect of the initial configuration on the tunneling dynamics of a few bosons for both odd and even numbers of bosons is studied, which results in intriguing consequences.     

Realization of Perfect Teleportation with W-States in Cavity QED

We put forward an experimentally feasible protocol for realizing a perfect teleportation by using a class of W-state in QED. The simple way of generating the entangled channel and distinguishing the measurement bases is the distinct feature of our scheme. In addition, the probability of teleportation is up to 100%. The scheme can be implemented by the present cavity QED techniques.