Decoherence for a two-qubit system in a spin-chain environment

The quantum coherence and correlation dynamics for a two-qubit system in the Ising spin-chain environment are studied. A sudden change of coherence is found near the critical point, which provides us with an effective way to detect the quantum phase transition. By studying the relationship between quantum discord and coherence, we find that coherence displays the behavior of classical correlation for t 〈 t0, and of quantum discord for t 〉 t0, where t0 is the time-point of a sudden transition between classical and quantum decoherence.

Teleportation of Superposition of Coherent States Using 4-Partite States and Effect of Decoherence on Fidelity

A scheme of teleporting a superposition of coherent states |α> and |-α> using a 4-partite state, a beam splitter and two phase shifters was proposed by N. Ba An (Phys. Rev. A, 68, 022321, 2003). The author concluded that the probability for successful teleportation is only 1/4 in the limit |α|→∞ and 1/2 in the limit |α|→∞. In this paper it is shown that the author’s scheme can be altered slightly so as to obtain an almost perfect teleportation for an appreciable value of |α|2. We find the minimum assured fidelity i.e., the minimum fidelity for an arbitrarily chosen information state, which we write MAF in this paper, for different cases. We also discuss the effect of decoherence on teleportation fidelity. We find that if no photons are counted in both final outputs, MAF, is still nonzero except when there is no decoherence and the initial state (the state to be teleported) is even coherent state. For non-zero photon counts, MAF decreases with increase in |α|2 for low noise. For high noise, however, it increases, attains a maximum value and then decreases with |α|2. The average fidelity depends appreciably on the initial state for low values of |α|2 only.

Nonclassicality and decoherence of the coherent superposition operation of photon subtraction and addition on the squeezed state

The statistical properties of m-coherent superposition operation（μa ＋ νa）^m on the single-mode squeezed vacuum state（M-SSVS） and its decoherence in a thermal environment are studied.Converting the M-SSVS to a squeezed Hermite polynomial excitation state,we obtain a compact expression for the normalization factor of M-SSVS,which is the Legendre polynomial of the squeezing parameter.We also derive the explicit expression of the Wigner function（WF） of the M-SSVS,and find the negative region of the WF in phase space.The decoherence effect on this state is then discussed by deriving the time evolution of the WF.Using the negativity of the WF,the loss of nonclassicality is then discussed.

Nonlocal advantage of quantum coherence and entanglement of two spins under intrinsic decoherence

We investigate the nonlocal advantage of quantum coherence(NAQC)and entanglement for two spins coupled via the Heisenberg interaction and under the intrinsic decoherence.Solutions of this decoherence model for the initial spin-1/2 and spin-1 maximally entangled states are obtained,based on which we calculate the NAQC and entanglement.In the weak region of magnetic field,the NAQC behaves as a damped oscillation with the time evolves,while the entanglement decays exponentially(behaves as a damped oscillation)for the spin-1/2(spin-1)case.Moreover,the decay of both the NAQC and entanglement can be suppressed significantly by tuning the magnetic field and anisotropy of the spin interaction to some decoherence-rate-determined optimal values.

G-CPT Symmetry of Quantum Emergence and Submergence—An Information Conservational Multiagent Cellular Automata Unification of CPT Symmetry and CP Violation for Equilibrium-Based Many-World Causal Analysis of Quantum Coherence and Decoherence

An equilibrium-based YinYang bipolar dynamic Generalization of CPT (G-CPT) symmetry is introduced based on energy/information conservational quantum emergence-submergence. As a bottleneck of quantum computing, quantum decoherence or collapse has been plaguing quantum mechanics for decades. It is suggested that the crux of the problem can trace its origin back to the incompleteness of CPT symmetry due to the lack of holistic representation for equilibrium-based bipolar coexistence. In this work, the notion of quantum emergence-submergence is coined as two opposite processes with bipolar energy/information conservation. The new notion leads to G-CPT symmetry supported by a Bipolar Quantum Cellular Automata (BQCA) interpretation of quantum mechanics. It is shown that the new interpretation further leads to the unification of electromagnetic particle-antiparticle bipolarity and gravitational action-reaction bipolarity as well as CPT symmetry and CP violation into a philosophically, geometrically and logically different quantum gravity theory. On one hand, G-CPT symmetry enables a Bipolar Quantum Agent (BQA) to emerge as a bipolar quantum superposition or entanglement coupled to a globally coherent BQCA;on the other hand, G-CP violation supports a causal theory of BQA submergence or decoupling from the global coherence. In turn, BQAs can submerge from one world but emerge in another within YinYang bipolar quantum geometry. It is suggested that all logical, physical, social, biological and mental worlds are bipolar quantum entangled under G-CPT symmetry. It is contended that G-CPT symmetry constitutes an analytical paradigm of quantum mechanics and quantum gravity—a fundamental departure from “what goes around comes around”. The new paradigm leads to a number of predictions and challenges.

Decoherence of Entangled States Calculated by a Systematic Approximate Method

在这篇论文，协调状态的近似(CA ) 方法被用来处理二个二状态的系统的纠缠的状态的 decoherence 的问题。作为讨论的底，一个二状态的系统的驱散起初被调查了。CA 计算的 Theimproved 结果在纸被给。CA 什么时候被用于结合的 twotwo 状态系统的驱散的问题，被显示出正确来临行为和可伸缩的法律被获得了环境。整个进化过程和纠缠的状态的 decoherence 的计算结果也显示出可伸缩的法律，正确来临行为，和富有的现象。

A Quantum Dynamical Mode for the Control of Decoherence

We present a quantum measurement model where the meter is taken to be a squeezed reservoir. We realize decoherence in macroscopic limits using Bogoliubov transformation, and this kind of system-meter coupling has a dramatic influence on decoherence.

Topological Effect of Reduced Quantum Trajectory in Coherence and Decoherence

The topological expression of the reduced quantum trajectory is given by using φ-mapping topologicalcurrent theory.The topological expression is used in study of the coherence and the decoherence.We find the expressionof vorticity for decoherence has a similar form as that for coherence.A topological reason leading to the decoherenceis given and a new parameter is defined to indicate the coherence degree.The parameter is different from the dampingfactor because it relates to the topological structure of the reduced quantum trajectory.

Intensity-independent molecular rotational decoherence lifetimes measured with mean wavelength shifts of femtosecond pulses

We report on an experimental investigation on the dynamic decoherence process of molecular rotational wavepackets during femtosecond laser filamentation based on time-dependent mean wavelength shifts of a weak probe pulse. Details of periodic revival structures of transient alignment can be readily obtained from the measured shifted spectra due to the periodic modulation of the molecular refractive index. Using the method, we measured decoherence lifetimes of molecular rotational wavepackets in N2and O2under different experimental conditions. Our results indicate that decoherence lifetimes of molecular rotational wavepackets are primarily determined by the relative population of rotational states in the wave packet and intermolecular collisions,rather than the focusing intensity.

Coherence rotation in dissipative reaction ^(19)F+^(51)V

Excitation functions of the projectile-like fragments in the dissipative reaction 19F+ 51V have been measured at θ1 =21.7°, 36.1° and 40.5°. The incident energies are from 102.25 to 109.50 MeV in 250 keV steps. The energy coherence width Γ and the rotation angular velocities ω of the corresponding dinuclear systems are extracted. The coherence rotation and its importance in the reaction process are discussed.

Stick-slip nonuniform rotation distortion correction in distal scanning optical coherence tomography catheters

We present a robust and fiducial-marker-free algorithm that can identify and correct stick-slip distortion caused by nonuniform rotation(or beam scanning)in distally scanned catheters for endoscopic optical coherence tomography(OCT)images.This algorithm employs spatial fre-quency analysis to select and remove distortions.We demonstrate the feasibility of this algorithm on images acquired from ex vivo rat colon with a distally scanned DC motor-based endoscope.The proposed algorithm can be applied to general endoscopic OCT images for correcting non-uniform rotation distortion.

非平衡等离子体流场相干反斯托克斯拉曼散射光谱计算及振转温度测量

高温非平衡问题是高超声速流动中最基本的科学问题之一,而热力学非平衡特性的准确表征是理解高温非平衡问题和高超声速空气动力学的基础,如何准确可靠地表征流场的热力学非平衡特性是解决高超声速飞行器在稀薄流域高温非平衡问题的关键.本文基于相干反斯托克斯拉曼散射基本原理,开发了面向非平衡流场的振转温度反演算法,并在宽温度范围静态环境开展验证.搭建了非平衡等离子体流场相干反斯托克斯拉曼散射测温实验平台并开展实验验证,结果表明微波等离子体处于热力学非平衡状态,并且振动温度和转动温度与微波功率成正比,而热力学非平衡度与微波功率成反比,当微波功率从80W增加至180 W时,等离子体电子数密度增加,中性粒子通过与电子碰撞获得能量使振动温度从(2201±43)K增加至(2452±56)K、转动温度从(382±20)K增加至(535±49)K;而处于振动激发态的分子通过振动-平动弛豫过程(对于N2分子弛豫速率与温度成正比)将部分振动能转化为平动能,导致振动温度与转动温度的差异降低,等离子体热力学非平衡度从0.83降低至0.78.

一种基于波束重置提高测角精度的方法

针对雷达天线转动时波束对回波信号产生调制,导致多脉冲积累雷达比幅测角时测量精度下降的问题,分析了测角精度恶化产生的机理,提出了基于波束重置提高测角精度的方法,并进行了仿真分析和试验验证.仿真和试验结果表明,该方法可行有效;当积累脉冲数较多时,与传统方法相比,本文提出的方法测量精度更高,适用范围更广.

Scale effect removal and range migration correction for hypersonic target coherent detection

The detection of hypersonic targets usually confronts range migration(RM)issue before coherent integration(CI).The traditional methods aiming at correcting RM to obtain CI mainly considers the narrow-band radar condition.However,with the increasing requirement of far-range detection,the time bandwidth product,which is corresponding to radar’s mean power,should be promoted in actual application.Thus,the echo signal generates the scale effect(SE)at large time bandwidth product situation,influencing the intra and inter pulse integration performance.To eliminate SE and correct RM,this paper proposes an effective algorithm,i.e.,scaled location rotation transform(ScLRT).The ScLRT can remove SE to obtain the matching pulse compression(PC)as well as correct RM to complete CI via the location rotation transform,being implemented by seeking the actual rotation angle.Compared to the traditional coherent detection algorithms,Sc LRT can address the SE problem to achieve better detection/estimation capabilities.At last,this paper gives several simulations to assess the viability of ScLRT.

Physics of quantum coherence in spin systems

Quantum computation provides a great speedup over its classical counterpart in solving some hard problems. The advantages of quantum computation come from the coherent superposition principle of quantum mechanics. Spin system is one of the most significant candidates to realize quantum computation. In this review, we focus on the recent experimental progress related to quantum coherence and some fundamental concepts such as the uncertainty principle in the spin systems.We shall first briefly introduce the quantum description of qubit, coherence, and decoherence. Based on this picture,preserving quantum coherence and detection of weak magnetic fields are presented. We also discuss the realization of precise quantum coherent control, adiabatic quantum factorization algorithm, and two aspects of uncertainty relations.

Classical-driving-assisted coherence dynamics and its conservation

We investigate the quantum coherence and quantum entanglement dynamics of a classical driven single atom coupled to a single-mode cavity. It is shown that the transformation between the atomic coherence and the atom-field entanglement exists, and can be improved by adjusting the classical driving field. The joint evolution of two identical single-body systems is also studied. The results show the quantum coherence transfers among composite subsystems, and the coherence conservation of composite subsystems is obtained. Moreover, the classical driving field can be used to suppress the decay of the coherence and entanglement, owing to considering the leaky cavity. The non-Markovian dynamics of the system is also discussed finally.

Organizing and Disorganizing Resonances of Microtubules, Stem Cells, and Proteins Calculated by a Quantum Equation of Coherence

Conformational states of microtubules and proteins have typical spatial-spectral arrangements of atoms, called spatial coherence, that are characteristic for building, homeostasis, decay, and apoptosis. Microtubules show a principle of a self-organizing-synergetic structure called a Fröhlich-Bose-Einstein state. The spatial coherence of this state can be described by a toroidal quantum equation of coherence. In this space, microtubules and proteins have typical discrete frequency patterns. These frequencies comply with two proposed quantum wave equations of respective coherence (regulation) and decoherence (deregulation), that describe quantum entangled and disentangled states. The proposed equation of coherence shows the following typical scale invariant distribution of energy: En = ħωref 2q3m. The proposed model supports quantum entanglement and is in line with the earlier published models of Fröhlich, Davydov, and Chern. A meta-analysis shows a semi-harmonic scale-invariant pattern for microtubules, stem cells, proteins, and EEG- and MEG-patterns. A fit has been found for about 50 different organizing frequencies and 5 disorganizing frequencies of measured microtubule frequencies that fit with the calculated values of the proposed quantum equations, which are positioned in a nested toroidal geometry. All measured and analysed frequencies of microtubules comply with the same energy distribution found for Bose-Einstein condensates. The overall results show a presence of an informational quantum code, a direct relation with the eigenfrequencies of microtubules, stem cells, DNA, and proteins, that supplies information to realize biological order in life cells and substantiates a collective Fröhlich-Bose-Einstein type of behaviour and further support the models of Tuszynski, Hameroff, Bandyopadhyay, Del Giudice and Vitiello, Katona, Pettini, and Pokorny.

Coherent population trapping magnetometer by differential detecting magneto–optic rotation effect

A pocket coherent population trapping（CPT） atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated.Using the differential detecting magneto–optic rotation effect,a CPT spectrum with the background canceled and a high signal-to-noise ratio is obtained.The experimental results reveal that the sensitivity of the proposed scheme can be improved by half an order,and the ability to detect weak magnetic fields is extended one-fold.Therefore,the proposed scheme is suited to realize a pocket-size CPT magnetometer.

Theoretical study of micro-optical structure fabrication based on sample rotation and two-laser-beam interference

A method for fabricating a micro-optical structure based on sample rotation and two-laser-beam interference is proposed. The rotation process is analyzed using the coordinate transformation in matrix presentation and the theoretical expressions of the optical field distributions corresponding to different sample rotations. By rotating the samples and changing the laser wavelength, various special micro-optical structures can be obtained, such as equally spaced concentric rings and irregular trapezoidal lattices; these structures are demonstrated by simulating the corresponding optical field distributions. The proposed approach may be developed into a low-cost laser interference lithography technology for the fabrication of various micro-optical structures.

The limit properties of spatial coherence of seismic ground motion

The limit properties of spatial coherence of seismic ground motion are studied based on the differential relation between rotation and translation in elastic theory, the results show that the empirical mathematical model of spatial coherence must satisfy some functional characteristics. It is also indicated that the key problem to estimate rotational power spectrum densities is to obtain precisely the two order derivative of spatial coherence.