Quantum extension of the Jarzynski relation: analogy with stochastic dephasing

The relation between the distribution of work performed on a classical system by an external force switched on an arbitrary time scale and the corresponding equilibrium free energy difference is generalized to quantum systems. Using the adiabatic representation, we show that this relation holds for isolated systems as well as for systems coupled to a bath described by a master equation. A close formal analogy is established between the present "classical trajectory" picture over populations of adiabatic states and phase fluctuations (dephasing) of a quantum coherence in spectral line shapes, described by the stochastic Liouville equation.     

Quantum memory for images with feedback

A spatially multimode scheme of the quantum memory for light is presented that can be considered to be a thin hologram, whose long-lived spin subsystem of a multiatomic ensemble stores image peculiarities, such as the multimode superposition and entangled quantum states, which is unattainable for ordinary holography. In the recording process, the measurement of polarization parameters of the transmitted light wave and the feedback are used for the action on an ensemble of fixed atoms (obtained, for example, by means of the laser cooling). The information capacity of a quantum hologram with a feedback will considerably exceed that of a spatially singlemode quantum memory.     

由多台全站仪组成的馈源舱位姿动态测量系统

介绍了大射电望远镜 FAST光机电一体化的创新设计。给出了通过测量馈源舱不共线三点的空间坐标来解算舱体位置和姿态的方法。提出以先进的高精度动态跟踪测量仪器徕卡 TCA2 0 0 3全站仪为基本测量单元 ,组合六台TCA2 0 0 3为一套馈源舱位姿动态测量系统。由于系统的测量精度可达到 1mm,因此不仅为馈源舱的闭环控制提供了检测手段 ,而且可应用 Stewart平台精调系统所提供的舱体位姿信息进行逆运动学模型计算。     

具有位移和绝对距离测量能力的回馈干涉系统

提出一种基于半导体激光器泵浦Nd∶YAG微片激光器的回馈干涉系统，适合于非配合目标的位移和绝对距离测量。该测量系统包括移频回馈干涉光学系统，基于泵浦调制的微片激光器调频系统和相敏检波信号处理系统3部分。介绍了移频回馈干涉的原理，给出了位移测量和绝对距离测量应用的原理和测量方法，分析了测量的分辨率。实际测量了发黑工件表面的位移和绝对距离。实验结果表明，该回馈干涉系统灵敏度高，对被测表面反射率的要求很低，兼有对非配合目标的高分辨率位移测量和绝对距离测量的能力。     

Quantum dot semiconductor laser with optoelectronic feedback

The optoelectronic feedback (OEF) in quantum dot semiconductor lasers (QD SLs) is studied theoretically where a model includes wetting layer ground state and excited state for QDs are included separating electrons and holes in their dynamics. Both positive and negative OEF are studied. The time series of photon density, the phase portraits of carriers in the states are studied. The parameters affecting OEF are examined where an excitability is seen. The QD SL is found to be more sensitive to the changes in time delay compared with other SLs and a complicated routs are seen in the behavior of QD SL.     

Quantum measurement with chaotic apparatus

We study a dissipative quantum mechanical model of the projective measurement of a qubit. We demonstrate how a correspondence limit, damped quantum oscillator can realise chaotic-like or periodic trajectories that emerge in sympathy with the projection of the qubit state, providing a model of the measurement process.     

Controlling a time-delay system using multiple delay feedback control

In this paper multiple delay feedback control (MDFC) with different and independent delay times is shown to be an efficient method for stabilizing fixed points in finite-dimensional dynamical systems. Whether MDFC can be applied to infinite-dimensional systems has been an open question. In this paper we find that for infinite-dimensional systems modelled by delay differential equations, MDFC works well for stabilizing (unstable) steady states in long-, moderate- and short-time delay regions, in particular for the hyperchaotic case.     

腔光力学系统中的量子测量

腔光力学系统近年来迅猛发展, 在精密测量、量子传感等方面已展现出重要的应用价值. 特别是与微纳技术和冷原子技术结合后, 这一系统正发展成为研究量子测量与量子操控的理想平台. 本文首先综述腔光力学在量子测量, 尤其是量子测量基础理论研究方面的进展; 然后分析腔光力学系统中的量子测量原理; 最后介绍我们近来在这方面的研究进展, 并通过我们设计的一系列新颖的基于腔光力学系统的量子测量方案来具体展示该系统在量子测量、量子操控等方面的潜在应用.     

Quantum feedback control for deterministic entangled photon generation

We present quantum feedback control for deterministic entanglement generation at the single-photon level. The protocol of controlling both total photon number and phase difference is based on the cascade structure of cavities placed in an optical closed loop, quantum nondemolition measurement with cross-Kerr interactions, and Lyapunov stability for feedback design.     

Optoelectronic instrumentation enhancement using data mining feedback for a 3D measurement system

3D measurement by a cyber-physical system based on optoelectronic scanning instrumentation has been enhanced by outliers and regression data mining feedback. The prototype has applications in (1) industrial manufacturing systems that include: robotic machinery, embedded vision, and motion control, (2) health care systems for measurement scanning, and (3) infrastructure by providing structural health monitoring. This paper presents new research performed in data processing of a 3D measurement vision sensing database. Outliers from multivariate data have been detected and removal to improve artificial intelligence regression algorithm results. Physical measurement error regression data has been used for 3D measurements error correction. Concluding, that the joint of physical phenomena, measurement and computation is an effectiveness action for feedback loops in the control of industrial, medical and civil tasks.     

Quantum heat switch with multiple qubits

We further elaborate on the device proposed by Karimi et al. [15], in which coupled superconducting qubits can play the role of a quantum heat switch. In the present paper we analyze the performances of the switch if the number of qubits increases considering in details the cases of three and four qubits. To this aim we study the effect of the number of qubits on the transmitted power between baths. As the number of qubits increases, the transmitted power between baths increases as well.     

Sinusoidal phase-modulating laser diode interferometer insensitive to intensity modulation for real-time displacement measurement with feedback control system

In sinusoidal phase modulating laser diode (LD) interferometer, the injection current of the LD is sinusoidally modulated to realize the modulation of the wavelength. However, the light intensity of LD is also modulated, which affects the measurement accuracy. An all-fiber sinusoidal phase modulating LD interferometer for real-time displacement measurement is proposed where the influence of the intensity modulation is eliminated with a new algorithm. It is made clear that an optimal depth of the sinusoidal phase modulation (SPM) exists in the algorithm. Moreover, the SPM depth is locked at the optimal value by controlling the injection current with a feedback control system. The feasibility of the proposed interferometer for displacement measurement is verified by experiments.     

Quantum estimation of detection efficiency with no-knowledge quantum feedback

We investigate that no-knowledge measurement-based feedback control is utilized to obtain the estimation precision of the detection efficiency. We show that no-knowledge measurement is the optimal way to estimate the detection efficiency.The higher precision can be achieved for the lower or larger detection efficiency. It is found that no-knowledge feedback can be used to cancel decoherence. No-knowledge feedback with a high detection efficiency can perform well in estimating frequency and detection efficiency parameters simultaneously; simultaneous estimation is better than independent estimation given by the same probes.     

Quantum measurement as a communication with nature

It is assumed that experiments yield results that are not isomorphic with reality, but represent a distorted image of reality. Reality is related to observation via a communication channel of finite capacity. Quantum uncertainties are due to the bound on the amount of information available. Use is made of recent results from information and communication theories.     

Quantum measurement and pure dephasing

The prerequisite of quantum measurement is a transformation of an initially off-diagonal density matrix _ρmα;nβ describing an interacting measured object and measuring device into a diagonal density matrix _{ρmα;mαδmnδαβ} . The latter density matrix describes a proper mixture of states having definitem-values. On the other hand, the irreversible relaxation (towards the thermodynamic equilibrium) is also characterized by transformation of an initially off-diagonal matrix into a diagonal one. It has been shown that the process of irreversible relaxation can be used to perform quantum measurement, provided the duration Δt of the measurement is much larger thanT ₂, the phase relaxation time, and much smaller thanT ₁, the population relaxation time:T ₂ ≪ Δt ≪T ₁. Agedanken experiment describing this kind of measurement is provided. Aπ/2-pulse transforms an initials _z = −1/2 state into superposition ofs _z = ±1/2 states. The irreversible relaxation leads to the proper mixture ofs _z = 1/2 ands _z = −1/2 state. Results of the measurements are verified by the second electromagnetic pulse.     

逐圈测量系统在合肥光源数字反馈调试中的应用

 使用逐圈测量系统作为观测手段,通过对逐圈测量系统采集所得数据进行分析,判断了数字反馈系统调试过程中的反馈效果。在改变六极铁电流以逐步改变储存环的色品值的过程中,通过逐圈测量系统观察了束流不稳定性,计算得到振荡增长时间和阻尼时间分别为0.258 ms和1.172 ms。并测量和计算了工作点、相空间等束流特性参数,分析了束流靠近和穿越5/9共振线的完整过程。     

逐圈测量系统在合肥光源数字反馈调试中的应用

使用逐圈测量系统作为观测手段,通过对逐圈测量系统采集所得数据进行分析,判断了数字反馈系统调试过程中的反馈效果。在改变六极铁电流以逐步改变储存环的色品值的过程中,通过逐圈测量系统观察了束流不稳定性,计算得到振荡增长时间和阻尼时间分别为0.258 ms和1.172 ms。并测量和计算了工作点、相空间等束流特性参数,分析了束流靠近和穿越5/9共振线的完整过程。