Quantum Effects of a Dissipative Mesoscopic Circuit with Mutual Inductance

We study the quantum fluctuations of the charge and current of two L-C dissipative mcsoscopic circuit withthe mutual inductance in the vacuum state. Our results show that the system state will evolve to a squerzcd coherentstate under the effect of external source. We find that the squeezing amplitude parameter is relative to the parametersof circuit and the mutual-inductance coefficient in the existence of dissipation. Whcn the circuit has no dissipation orthere is complete coupling between two meshes, the squeezing amplitude parameter only depends on the capacitance'sratio.     

Quantum Effects of a Dissipative Mesoscopic Circuit with Mutual Inductance

We study the quantum fluctuations of the charge and current of two L-C dissipative mesoscopic circuit with the mutual inductance in the vacuum state.Our results show that the system state will evolve to a squeezed coherent state under the effect of external source.We find that the squeezing amplitude parameter is relative to the parameters of circuit and the mutual-inductance coefficient in the existence of dissipation.When the circuit has no dissipation or there is complete coupling between two meshes,the squeezing amplitude parameter only depends on the capacitance‘s ratio.     

Construction of Laguerre polynomial's photon-added squeezing vacuum state and its quantum properties

Laguerre polynomial's photon-added squeezing vacuum state is constructed by operation of Laguerre polynomial's photon-added operator on squeezing vacuum state. By making use of the technique of integration within an ordered product of operators, we derive the normalization coefficient and the calculation expression of (a^1a^+). Its statistical properties, such as squeezing, the anti-bunching effect, the sub-Poissonian distribution property, the negativity of Wigner function, etc., are investigated. The influences of the squeezing parameter on quantum properties are discussed. Numerical results show that,firstly, the squeezing effect of the 1-order Laguerre polynomial's photon-added operator exciting squeezing vacuum state is strengthened, but its anti-bunching effect and sub-Poissonian statistical property are weakened with increasing squeezing parameter;secondly, its squeezing effect is similar to that of squeezing vacuum state, but its anti-bunching effect and subPoissonian distribution property are stronger than that of squeezing vacuum state. These results show that the operation of Laguerre polynomial's photon-added operator on squeezing vacuum state can enhance its non-classical properties.     

与压缩真空库耦合的单模腔内三量子点中激子纠缠

研究了与压缩真空库场耦合的单模腔中三个量子点中激子间纠缠的动力学行为.结果表明：如果不考虑腔模与激子吸收，激子演化为纯的纠缠态.当腔场与一压缩真空库耦合时，激子间形成混合三模高斯纠缠态；在长时极限下，激子态为一稳定的混合三模高斯纠缠态.通过求解激子的特征函数，发现激子态的纯度与纠缠不仅依赖于腔场的初态，并且还与库的双光子关联强度密切相关. 关键词： 纠缠 纯度 压缩真空库 量子点     

压缩真空场与原子非线性作用系统中场熵的压缩特性

利用量子信息熵理论,研究了附加克尔介质的压缩真空场与二能级原子依赖强度耦合相互作用系统中场熵的压缩特性.讨论了初始压缩真空场的压缩度以及克尔非线性作用的强度对场熵压缩特性的影响.结果表明,无克尔介质量,场熵压缩的演化具有严格的周期性.克尔介质的非线性作用的强弱可以改变场熵压缩的周期性.在初始压缩真空场的压缩度较大(r=5)时,无论克尔介质作用的强弱如何变化,场熵始终处于被压缩状态.     

Two-mode Gaussian states as resource of secure quantum teleportation in open systems

For secure quantum teleportation (SQT) of coherent states two conditions are necessary to be fulfilled: Gaussian-state resources with two-way steering and teleportation fidelity higher than 2/3. We investigate and compare squeezed thermal states and squeezed vacuum states as initial resource states for SQT in an open quantum system, consisting of two uncoupled harmonic oscillators interacting with a thermal environment. The evolution of the open system is obtained in terms of the covariance matrix, by using the Gorini-Kossakowski-Lindblad-Sudarshan master equation. The SQT conditions are satisfied in a longer period of time in the case of initial squeezed vacuum states, therefore these states are better resource states for SQT than squeezed thermal states. We show that the admissible time for SQT decreases by increasing temperature, dissipation coefficient and average number of thermal photons, while for greater values of the squeezing parameter, SQT conditions are satisfied in a longer period of time.     

Dynamical Casimir effect in dissipative superconducting circuit system

We investigate the possibility of observing in integrated solid-state systems the dynamical Casimir effect, in which photons are created out of vacuum. We use a transmission line resonator on a superconducting chip as the microwave cavity and modulate its properties by coupling it to carefully designed Josephson devices. We evaluate the effect of main decoherence sources and show that our design offers a promising system for experimentally demonstrating the dynamical Casimir effect. Moreover, we also study the squeezing properties of the created photon field and how they depend on the dissipation.     

Two-mode squeezing in a coherently driven degenerate parametric down conversion

Squeezing properties of a two-mode radiation produced by a process of driven degenerate parametric down conversion, when the cavity is coupled to two independent squeezed vacuum reservoirs employing the linearization procedure, are analyzed. The two-mode cavity and output radiations exhibit considerable squeezing even when the oscillator is coupled to a vacuum reservoir. One of the effects of coupling the cavity to the squeezed vacuum reservoirs is to increase the degree of squeezing exponentially. For the output radiation the correlation of the quadrature operators evaluated at different times also contributes to the squeezing, which is the reason for quenching of the overall noise in one of the quadrature components of the fundamental mode.     

压缩真空场与原子非线性作用系统中原子的量子特性

研究了附加克尔介质的压缩真空场与二能级原子依赖强度耦合相互作用系统中原子的反转特性,并采用密度算符间的距离研究了该模型中原子量子态的演化规律.详细地讨论了克尔非线性作用的强度以及初始压缩真空场的压缩度对原子反转和原子量子态演化的影响.     

二能级原子与压缩光场相互作用中的原子压缩效应

文中采用时间学业伦算符，考察到初始原子相干性及失谐量，研究了单个二能级原子与压缩真态辐射场相互作用中原子的偶极压缩。研究表明，对于各种不同的初始原子态，失谐量对双光子Ｊａｙｎｅｓ－Ｃｕｍｍｉｎｇｓ模型中的原子压缩行为都将产生很大的影响。通过数值计算，还讨论了初始压缩光场的压缩参数对原子压缩的影响。     

迭加态与压缩效应增强

本文运用量子力学态迭加原理,讨论由真空态和压缩态的迭加态获取更深压缩光场的可能性。结果表明,对弱场强浅压缩光场压缩加强效应非常显著;并且在迭加态中还呈现出反聚束的非经典效应。 关键词：     

动力学压缩真空中的Van der Waals力

基于参数动力学过程产生的压缩效应,利用Millonni源理论方法研究了 动力学压缩真空中Van der Waals力的性质及其与真空压缩的关系。所得结果表明：Van der Waals力的性质依赖于真空压缩的程度;在一定的临界条件下,Van der Waals力由通常的 吸引性作用转化为排斥性作用。当压缩系数为零时,所得结果与通常文献完全一致。     

压缩真空场与原子非线性作用过程中的纠缠与消纠缠

用Von Neumann熵研究了附加克尔介质的压缩真空场与二能级原子依赖强度耦合相互作用量子体系的量子纠缠特性.讨论了初始压缩真空场的压缩度以及克尔非线性作用的强度对该量子体系纠缠特性的影响.结果表明，克尔介质的非线性作用的强弱可以改变体系量子纠缠的周期性；在初始压缩度较大（r=5）时，克尔介质的非线性作用可导致原子与场持续地处于最大纠缠态，无消纠缠态或持续地处于消纠缠态. 关键词： 压缩真空态 克尔介质 依赖强度耦合J-C模型 Von Neumann熵 量子纠缠     

Phase properties of squeezed states of light

Recently introduced unitary and hermitian phase operators are used to examine the phase properties of squeezed states of light with particular reference to the squeezed vacuum. The results differ markedly from previous calculations involving the Susskind and Glogower operators. The new formalism allows the construction of a phase probability density which, on a polar diagram, is a circle for the vacuum state, becomes elliptical with gentle squeezing and collapses to a line through the origin for full squeezing. This probability density together with the calculation of expectation values of various trigonometrical functions of phase show how squeezing impresses phase information onto the vacuum.     

Atomic-dipole squeezing for arbitrarily prepared atom and field in multi-photon interaction

Summary The atomic-dipole squeezing condition for arbitrarily prepared atomic and field states in multi-photon Jaynes-Cummings model was derived. Three special cases were discussed. For the field initially in a vacuum state and a certain eigenstate of the Susskind-Glogower phase operator, the analytical dipole squeezing conditions were obtained and the maximum squeezing values were calculated. For a squeezed vacuum input field, the dipole squeezing behaviours under the influence of the field squeezing parameterr and the phased atom were numerically treated.     

低分析频率压缩光的实验制备

基于PPKTP晶体的阈值以下光学参量振荡(OPO)过程,制备了共振于铷原子D1线795 nm的压缩真空态光场,研究了分析频率处于千赫兹范围的主要噪声来源,特别是795 nm激光及其二次谐波397.5 nm激光在晶体内吸收引起的非线性损耗增加和系统热不稳定的问题(397.5 nm激光处于PPKTP晶体透光范围边缘,具有高于其他波长数倍的吸收系数).以795 nm和1064 nm为例,分析了非线性损耗及晶体内热效应对压缩度的影响.受限于以上因素,795 nm压缩光很难得到1064 nm波段同样的压缩度.探测系统中的噪声耦合则限制了压缩频带.实验上对分析频率为千赫兹的经典噪声进行了有效控制,通过使用真空注入的OPO、垂直偏振及反向传输的腔长锁定光、低噪声的平衡零拍探测器、高稳定度的实验系统及量子噪声锁定等方法,最终在2.6—100 kHz的分析频段得到了约2.8 dB的795 nm压缩真空.该压缩光可用作磁场测量系统的探测光以提高测量灵敏度.     

Quantum Properties of the State via Operation of Superposition of Photon Subtraction Two Times and Photon Addition Two Times on Two Modes Squeezing Vacuum State

Superposition of photon subtraction two times and photon addition two times excited two modes squeezing vacuum state (SPSAESVT) is introduced, which is generated by operation of superposition of annihilation operator and creation operator on two modes squeezed vacuum state. Non-classical properties of SPSAESVT, such as squeezing effect, anti-bunching effect, the violation of Cauchy-Schwartze inequality and the entanglement property between two modes, are investigated. Using numerical methods, the influences of the superposition coefficient of operators and that of squeezing parameter on its non-classical properties are discussed. The results show that SPSAESVT does not display antibunching effect, but it displays squeezing effect, and there are the violation of Cauchy-Schwartze inequality and the entanglement between two modes. Further, its squeezing effect is not affected by the superposition coefficient of the operators, but there is a nonlinear relationship both between the violation of Cauchy-Schwartze inequality and the superposition coefficient, and between the entanglement property and the superposition coefficient. As squeezing parameter increases, its squeezing effect and entanglement property are strengthened, but the violation of Cauchy-Schwartze inequality is weakened.     

Quantum entanglement and nonlocality properties of two-mode Gaussian squeezed states

Quantum entanglement and nonlocality properties of a family of two-mode Gaussian pure states have been investigated. The results show that the entanglement of these states is determined by both the two-mode squeezing parameter and the difference of the two single-mode squeezing parameters. For the same two-mode squeezing parameter, these states show larger entanglement than the usual two-mode squeezed vacuum state. The violation of Bell inequality depends strongly on all the squeezing parameters of these states and disappears completely in the limit of large squeezing. In particular, these states can exhibit much stronger violation of local realism than two-mode squeezed vacuum state in the range of experimentally available squeezing values.     

多光子非线性过程中的振幅平方压缩

本文研究了多光子非线性光学过程中的振幅平方压缩,证明了K光子么正算符Sk(z)(K>2)对非真空相干态的作用在—级近似下会产生振幅平方压缩.以及Sk(z)(K>2,K≠4)对真空态的作用不会产生振幅平方压缩.发现4个光子么正算符S4(z)对真空态的作用可以产生振幅平方压缩,这表明振幅平方压缩是一种独立于二阶压缩、反聚束以及亚泊松统计分布的新的光场非经典效应.     

Polarization squeezing with cold atoms

We study the interaction of a nearly resonant linearly polarized laser beam with a cloud of cold cesium atoms in a high finesse optical cavity. We show theoretically and experimentally that the cross-Kerr effect due to the saturation of the optical transition produces quadrature squeezing on both the mean field and the orthogonally polarized vacuum mode. An interpretation of this vacuum squeezing as polarization squeezing is given and a method for measuring quantum Stokes parameters for weak beams via a local oscillator is developed.