有限温度下介观无损耗传输线中电流的量子涨落

利用热场动力学的方法研究了介观无损耗传输线中电流在具有热噪声的真空态、相干态和压缩态下的量子涨落.得到了有限温度下介观无损耗传输线中电流的量子涨落与温度的关系.结果表明,介观无损耗传输线中电流的量子涨落不仅与电路的参数有关,还与传输线所处的环境温度有关.温度越高,介观无损耗传输线中的量子噪声越大.     

介观RLC电路在热相干态和热压缩态下的量子涨落

利用热场动力学的方法研究了介观RLC电路在有限温度下的相干态和压缩态中电荷和磁通量的量子涨落.结果表明,介观RLC电路中电荷和磁通量的量子涨落不仅与电路中的元件参数而且可能与环境温度和压缩参数有关,而这些量子涨落与平移参数无关.     

Fock空间中基于波色双模指数二次型算符的连续变量纠缠态的量子涨落特性

利用线性量子变换理论（LQTT）,导出在Fock空间中连续变量两体纠缠态的量子涨落计算的一般公式,并讨论此纠缠态的压缩特性。通过线性拟合的方法,得到当涨落度和纠缠熵分别出现极值时,态参数之间关系。结果显示当达到较大纠缠时,该态的压缩程度也较大,除此以外还得到了涨落度随参数和纠缠熵的变化关系。同时举例说明此公式在计算双模压缩真空态和单边双模压缩真空态的量子涨落中的应用。     

热真空下介观RLC电路的量子涨落

在真空态和热真空态下讨论了介观RLC电路的量子涨落。结果表明电荷和电流的量子力学零点涨落随着温度增加。     

量子化介观RLC并联电路在热真空态下的量子效应

根据热场动力学理论,研究了具有普遍意义的量子化介观RLC并联电路在热真空态下产生的量子效应,并分析在各支路中电流和电压的量子涨落与电路元件、环境热真空态以及时间三个方面因素的关系。结果表明,处于热真空态下的量子化介观RLC并联电路,各支路电流和电压的量子涨落均受到这三个方面因素的影响, 并且具有如下规律, 电流和电压的涨落均随时间按指数规律衰减,但衰减速度仅与电路元件的参数有关,而初始时刻涨落的大小由电路元件参数和环境热真空态的温度共同决定。     

介观RLC电路的量子化及其在有限温度下的量子效应

利用正则化变换,给出了介观RLC电路体系的量子化方案.借助数值计算的方法,研究了体系热真空态的Wigner函数随温度变化的规律,同时借助量子算符及其Weyl-Wigner对应研究了体系中电荷及自感磁通量在热真空态下的量子效应.结果表明,低温下热真空态的Wigner函数为一稳定的波包,随温度升高,波包逐渐扩散;体系中电荷及自感磁通量在热真空态下的的量子涨落除与电路参数相关外,还与温度及时间密切相关.     

有限温度下介观LC电路中的量子涨落

在有限温度下,介观电路系统实际上并不处在一个确定的量子状态,而是处在混合态.利用量子正则系综理论研究了介观LC电路在混合态下电荷和电流的量子涨落.结果表明,有限温度下介观LC电路中的量子涨落不仅与电路器件参数有关,而且与温度也有关.温度越高,电路中的量子涨落越大.该方法较热场动力学(TFD)方法更易于理解和应用.由于实际的介观电路总是处在有限温度下,所以其结论对控制介观电路中的量子涨落有一定的实际意义.     

振幅薛定谔猫态下介观耗散传输线的压缩特性

在介观耗散传输线量子化的基础上，研究了振幅薛定谔猫态下该传输线的压缩特性．结果表明，传输线中电流及单位长度传输线电感上电压的量子噪声的压缩性质不仅取决于振幅薛定谔猫态，也与传输线的分布参数和位置有关．平均光子数为1时，量子噪声可得到最大压缩。     

三网孔介观电容耦合电路的量子效应

本文将三网孔介观电容耦合电路系统看作一个正则系综，通过计算正则系综的密度矩阵方程得出有限温度下耦合电路中电荷和磁通量的量子涨落．高频下，电路中电荷的量子涨落类似于低温下的情形，表现为典型的量子噪音；磁通量的量子涨落则不单是零点的量子涨落，总是和温度有关；绝对零度下，输入、输出网孔中电荷和磁通量不确定度的乘积保持相等．     

数-相量子化及介观电路在自由热态下的量子效应

利用数-相量子化方案,将介观LC电路等效为一个谐振子.通过相干态表象和算符正规乘积形式,简捷地给出了自由热态的Wigner函数,同时借助于量子算符及其Weyl-Wigner对应研究了体系中电荷数及相位差在自由热态下的量子效应.结果表明,体系中电荷数及相位差在自由热态下的量子涨落不仅和电路中器件的参数有关,而且还和温度有关,且储存于电感中的平均能量和电容中的平均能量分别相等.这一研究结果支持了介观电路数-相量子化新方案,对介观电路的量子化和电路的量子效应的研究具有很好的理论指导意义.     

Quantum fluctuations of mesoscopic damped mutual capacitance coupled double resonance RLC circuit in thermal excitation state

With the rapid development of microelectronics and na- nometer techniques, the trend of the miniaturization of cir- cuits and devices becomes stronger and stronger. The quan- tum effects of mesoscopic system have become one hotspot in condensed matter phy…     

A Method of Calibration of Terahertz Wave Brightness Under Nonlinear-Optical Detection

A new method is proposed for calibration of the terahertz wave spectral brightness. The method is based on the use of quantum and thermal field fluctuations as intrinsic references under nonlinear-optical detection. Both effective brightness of the thermal fluctuations and temperature of the laser-pumped nonlinear-optical crystal can be measured absolutely within the calibration procedure also. It is shown that the accuracy of the terahertz wave brightness calibration is strongly dependent on the value of the terahertz wave losses in the nonlinear-optical crystal. The scheme of quasi-phase matched terahertz wave detection in periodically poled lithium niobate is considered. Dispersion of the absorption coefficient in the terahertz frequency range is measured by a three-frequency interference method under spontaneous parametric down-conversion for nominally pure and Mg-doped lithium niobate crystals. The influence of the terahertz radiation losses in Mg-doped lithium niobate crystals is estimated.     

有限温度下生物细胞中电流电压的量子涨落

在介观生物细胞等效电路量子化的基础上通过热正则Bogoliuov变换，研究了有限温度下介观生物细胞中电流和电压的量子涨落。结果表明，介观生物细胞中电流电压的量子涨落不仅与其等效电路的参数有关，还与温度有关，且随时间衰减。     

The classical and quantum theory of thermal magnetic noise, with applications in spintronics and quantum microscopy

Thermal fluctuations generate magnetic noise in the vicinity of any conductive and/or magnetically permeable solid. This magnetic noise plays a fundamental role in the design of spintronic devices: namely, it sets the time scale during which electron spins retain their coherence. This paper presents a rigorous classical and quantum analysis of thermal magnetic noise, together with practical engineering examples. Starting with the fluctuation-dissipation theorem and Maxwell's equations, a closed-form expression for the spectral density of thermal magnetic noise is derived. Quantum decoherence, as induced by thermal magnetic noise, is analyzed via the independent oscillator heat bath model of Ford et al. The resulting quantum Langevin equations yield closed-form expressions for the spin relaxation times. For realistic experiments in spintronics, magnetic resonance force microscopy, Bose-Einstein condensates, atomic physics, and solid-state quantum computing, the predicted relaxation rates are rapid enough that substantial experimental care must be taken to minimize them. At zero temperature, the quantum entanglement between a spin state and a thermal reservoir is computed. The same Hamiltonian matrix elements that govern fluctuation and dissipation are shown to also govern entanglement and renormalization, and a specific example of a fluctuation-dissipation-entanglement theorem is constructed. We postulate that this theorem is independent of the detailed structure of thermal reservoirs, and therefore expresses a general thermodynamic principle.