Coherent electron pair. Electromagnetic field
Constantin V. Usenko, Nataliia O. Cherkashyna
借助四极矩和磁矩，证明了相干电子对的相对坐标和动量具有可观量的意义。给出了标量势四极项的分布。这些分布具有非经典性质。
It is shown that relative coordinate and momentum of coherent electron pair have the meaning of observables with the help of quadrupole and magnetic moments. Distributions of quadrupole terms of scalar potential are shown. These distributions have nonclassical properties.
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Electromagnetically induced coherent backscattering
我们证明了一个强大的相干后向波振荡只使用向前传播的领域。这是通过将激光场施加到具有适当选择的失谐的超色散介质以激发对应于后向传播波的分子振动相干性来实现的。因此，物理学与超慢光的传播有许多共同之处。应用相干散射和遥感进行了讨论。
Coherent control of light field with electromagnetically induced transparency in a dark state Raman coherent tripod system
在标准$Λ$型方案中，利用相干布居俘获引起的两原子能级相干叠加，形成一个三脚架型系统。一个弱的探测脉冲扫描整个系统所示，经历一个交叉从吸收透明，然后放大。因此，探测脉冲的群速度可以被控制为以亚光速、标准速度、超光速甚至负速度传播。结果表明，光场的传播行为完全由相干叠加的初态决定和控制。
Semiclassical trajectory-coherent approximation in quantum mechanics: II. High order corrections to the Dirac operators in external electromagnetic field
得到了具有反常Pauli相互作用的Dirac算符的半经典相干态和半经典格林函数的高近似解。对于薛定谔算子和狄拉克算子，可以构造任意精度的关于h，h-->0的连续相干表示。
Coherent optical detection of highly excited Rydberg states using electromagnetically induced transparency
在室温铷原子蒸气池中，通过将5 p态与Rydberg态（ns或nd，n=26 ~ 124）耦合，观察到5s ~ 5 p跃迁的电磁感应透明（EIT）。我们证明，窄线宽的EIT共振（2 MHz）允许精确测量的d状态精细结构分裂，并连同灵敏度的里德堡态的电场，我们能够检测瞬态电场产生的动态细胞内的电荷。里德伯态通过EIT的相干耦合也可以用于交叉相位调制和光子纠缠。
We experimentally demonstrate coherent amplification of probe field in a tripod-type atoms driven by strong coupling, signal and weak probe fields. We suppress linear and nonlinear atomic absorptions for resonant and near resonant probe via double electromagnetically induced transparency (DEIT). Combining these advantages of suppressed absorption along with temperature- or atomic-density-controlled transfer of population(ToP) between hyperfine ground states, we can induce near-resonant amplification of probe through stimulated Raman scattering(SRS) pumped by low-intensity signal field. The inc…
The development of efficient protocols for pure and mixed states preparation is challenging task. Most of the theory of quantum information applications has been developed for fully coherent or completely incoherent light. However, in many situations of interest partially coherent light has been proved to be a more robust model of radiation. In this paper the underpinning theory of two photon amplitude functions for down-converted fields with partially coherent pump beams is investigated. By using the generalised Siegert relations and the coherent mode representation of the cross spectral dens…
In the present article we extend our study (BJP 45 (2015) 369) of generalized coherent states (GCS) of a one-dimensional particle considering such important physical system as a 3-dimensional charged particle in electric and magnetic fields. Constructing GCS in many-dimensional case, we meet nontrivial technical complications that make the consideration nontrivial and instructive. The GCS of a system under consideration are constructed. We study properties of these GCS such as completeness relations, minimization of uncertainty relations and so on. We point out which family of the obtained GCS…
Generation of entangled coherent states via cross phase modulation in a double electromagnetically induced transparency regime
纠缠相干态的产生是利用相干态进行量子信息处理的重要组成部分。最近，已经提出了许多方案来实现这一任务。为了产生行波纠缠相干态，交叉相位调制，优化的光学克尔效应增强在电磁诱导透明（EIT）制度的稠密介质中，似乎是非常有前途的。在这种情况下，我们提出了一个完全量化的模型，最近提出的双EIT计划[D。Petrosyan和G. Kurizki，{ \sl Phys.Rev.A} { \bf 65}，33833（2002）]：采用完全哈密顿方法执行量化步骤。这使我们能够为两个相互作用的量子光场写出有效的运动方程，表明一个场的动力学如何取决于另一个场的光子数算符。薛定谔猫态是两个不同相干态的叠加态，其制备过程被简单地揭示出来。这是基于经由两个光场（最初以相干态制备）的双EIT的非线性相互作用以及基于使用$50:50$分束器和两个光电检测器执行的检测步骤。为了显示所产生的纠缠相干态的纠缠，我们建议测量光场的联合正交方差。我们证明了纠缠相干态满足基于正交方差测量的纠缠的充分条件。我们还展示了我们的方案是如何强大的零差检测器的低检测效率。
We present a self-consistent mean-field model based on a two-component Pauli-like equation that incorporates quantum and relativistic effects (up to second-order in 1/c) for both external and internal electromagnetic fields. By taking the semi-relativistic limit of the Dirac-Maxwell equations in the presence of an external electromagnetic field we obtain an analytical expression of a coherent light-induced mean-field Hamiltonian. The latter exhibits several mechanisms that involve the internal mean fields created by all the electrons and the external electromagnetic field (laser). The role pla…
Dark-State Polaritons in Electromagnetically Induced Transparency
我们确定形式稳定的耦合激发光和物质（“暗态极化激元”）与电磁感应透明中的量子场的传播。暗态极化激元的性质如群速度由光和物质成分之间的混合角决定，并且可以在脉冲传播时由外部相干场控制。特别是，光脉冲可以被减速和“捕获”，在这种情况下，它们的形状和量子态被映射到物质的亚稳态集体态上。这种可逆的相干控制技术的可能应用进行了讨论。
Electromagnetic Selection Rules and Coherent Manipulation of Quantum Skyrmion via Surface Acoustic Wave Phonons
本研究通过表面声波声子实现量子斯格明子的相干操控，揭示了电磁选择定则，并发现耦合强度随斯格明子半径线性增强，为混合量子信息处理提供了紧凑构建模块。
Spatial confinement effects on quantum field theory using nonlinear coherent states approach
通过对变形谐振子代数的研究，我们研究了一些基本的量子限制效应。在非线性相干态理论的框架内，我们证明了量子谐振子的空间限制效应可以用形变函数来表示。利用变形代数，我们构造了一个有限空间中的量子场论。特别是，我们发现，禁闭影响的一些物理性质的电磁场，它引起的非线性相互作用。此外，我们还提出了一种在有限区域内产生与电磁场相关的非线性相干态的物理方案。
In coherent control, electromagnetic vacuum fluctuations usually cause coherence loss through irreversible spontaneous emission. However, since the dissipation via emission is essentially due to correlation of the fluctuations, when emission ends in a superposition of multiple final states, correlation between different pathways may build up if the "which-way" information is not fully resolved (i.e., the emission spectrum is broader than the transition energy range). Such correlation can be exploited for spin-flip control in a $Λ$-type three-level system, which manifests itself as an all-optic…
A class of states of the electromagnetic field involving superpositions of all the excited states above a specified low energy eigenstate of the electromagnetic field is introduced. These states and the photon-added coherent states are shown to be the limiting cases of a generalized photon-added coherent states. This new class of states is nonclassical, non-Gaussian and has equal uncertainties in the field quadratures. For suitable choices of parameters, these uncertainties are very close to those of the coherent states. Nevertheless, these states exhibit sub-Poissonian photon number distribut…
A system of $N_a$ atoms of $n$-levels interacting dipolarly with $\ell$ modes of electromagnetic field is considered. The energy surface of the system is constructed from the direct product of the coherent states of U$(n)$ in the totally symmetric representation for the matter times the $\ell$ coherent states of the electromagnetic field. A variational analysis shows that the collective region is divided into $\ell$ zones, inside each of which only one mode of the electromagnetic field contributes to the ground state. In consequence, the polychromatic phase diagram for the ground state natural…
Entanglement of superposition and pair coherent states
利用叠加态纠缠研究了相干态对的纠缠特性。结果表明，在谐振子基下，对相干态的展开中只有少数几个态对纠缠有显著贡献。我们还研究了一个两对相干态叠加的情形
Integrals of motion and statistical properties of quantized electromagnetic field (e.-m. field) in time-dependent linear dielectric and conductive media are considered, using Choi-Yeon quantization, based on Caldirola-Kanai type Hamiltonian. Eigenstates of quadratic and linear invariants are constructed, the solutions being expressed in terms of a complex parametric function that obeys classical oscillator equation with time-varying frequency. The time evolutions of initial Glauber coherent states and Fock states are considered. The medium conductivity and the time-dependent electric permeabil…
In NMR experiments, interaction of quantized radio-frequency (rf) field leads to entanglement of nuclear spin with the electromagnetic field. In an entangled state, the nuclear spins are depolarized with no net magnetization, which cannot give a detectable signal in inductive detection. We show that when the electromagnetic field is in coherent state, inductive detection is just true. We develop the mathematics to study the evolution of a coherent rf-field with a sample of all polarized spins. We show that evolution can be solved in closed form as a separable state of rf-field and spin ensembl…
Quantitative measures of entanglement in pair coherent states
双模辐射场的成对相干态属于一类非高斯波函数态。研究了这类态的两模间的量子纠缠性质和非经典性特征。在对相干态的背景下研究了现有的不可分性判据。
High coherent solid-state qubit from a pair of quantum dots
在这篇文章中，我们提出了一个由两个耦合的量子点构建高相干固态量子比特的方案。量子信息存储在电子-空穴对态中，电子和空穴位于不同的点上，通过虚交换腔光子的有效耦合作用，实现了包含任意一对量子比特的通用量子门。
We consider the influence of a resonant control field on weak localization of light in ultracold atomic ensembles. Both steady-state and pulsed light excitation are considered. We show that the presence of a control field essentially changes the type of interference effects which occur under conditions of multiple scattering. For example, for some scattering polarization channels the presence of a control field can cause destructive interference through which the enhancement factor, normally considered to be greater than one, becomes less than one.
After reviewing parity measurement based interferometry with twin-Fock states, which allows for super-sensitivity (Heisenberg-limited) and super-resolution, we consider interferometry with two different superpositions of twin-Fock states, namely two-mode squeezed vacuum states and pair coherent states. This study is motivated by the experimental challenge of producing twin-Fock states on opposite sides of a beam splitter. We find that input two-mode squeezed states, while allowing for Heisenberg-limited sensitivity, do not yield super-resolutions, whereas we that find both are possible with in…
We study the evolution of entangled coherent states of the two quantized electromagnetic fields under dissipation. Characteristic time scales for the decay of the negativity are found in the case of large values of the phase space distance among the states of each mode. We also study how the entanglement emerges among the reservoirs.
Cluster-type entangled coherent states
提出了团簇型纠缠相干态，并讨论了它们的性质。一个腔QED产生方案，使用适当的选择原子-腔相互作用，通过失谐调整和经典外场的应用，得到的。在实现简单的原子测量之后，可以生成表示分离腔中的非局域电磁场的CTECS。
Here a special case of perturbation in quantum harmonic oscillator is studied. Here we assume the perturbed potential to be a Harmonic Oscillator that has been shifted in the position space.We construct the new creation and annihilation operators for the new Hamiltonian to find out its energy eigenstates. What is interesting about the solution of this system is that we find out that the ground state of this system is a coherent state of the ground state of the original harmonic oscillator. We know that the Hamiltonian of electromagnetic field is similar to that of the harmonic oscillator where…
Closing the gap of secure quantum key rate with the Heralded Pair-Coherent States
本文研究了量子密码协议中弱相干脉冲（WCP）和预言单光子源（HSPS）实现的量子密钥速率之间长期存在的差距。我们证明了，通过使用先驱对相干态（HPCS）光子源，这样的差距实际上可以填补在BB84和SARG量子密钥分发。这样，就得到了一个在每个传输距离上都能达到最佳密钥速率的通用光子源。
We examine entanglement between number and polarization, or between number and relative phase, for pairs of coherent states and two-mode squeezed vacuum via linear entropy and covariance criteria. We consider the embedding of the two-mode Hilbert space in a larger space to get a well-defined factorization of the number-phase variables. This can be regarded as a kind of proto-entanglement that can be extracted and converted into real particle entanglement via feasible experimental procedures. In particular this reveals interesting entanglement properties of pairs of coherent states.
Anisotropic harmonic oscillator in a static electromagnetic field
研究了非相对论带电粒子在各向异性谐振子势和均匀静态电磁场中的运动。几种配置的电磁场被认为是。在大多数情况下，薛定谔方程是解析解。明确地得到了能级和波函数。在某些情况下，得到的基态不是最小波包，尽管它是高斯型的。详细讨论了相干态和压缩态及其时间演化。
U(2) invariant squeezing properties of pair coherent states
用U（2）不变方法研究了对相干态的压缩特性。这种方法有助于全面分析双模态的压缩特性。我们使用Sp（4，R）的最大紧致子群U（2）来混合模式，从而使我们能够搜索所有可能的平方以进行压缩。对相干态的方差矩阵原来是解析对角化的，给我们一个处理它的最小本征值，通过它，我们能够牵制这些状态的压缩特性。为了明确地说明U（2）变换所起的作用，我们将我们的结果与先前对相干态压缩的分析联系起来。
Dark pair coherent states of the motion of a trapped ion
本文提出了一个在二维阱中产生离子运动振动对相干态的方案。在我们的方案中，被囚禁的离子在离子阱的X-Y平面内被三束沿不同方向的激光束双色激发。我们表明，如果初始振动状态是由一个双模Fock态，最终的稳定状态，由离子发射的荧光的消光表示，是一个纯态。处于平衡态的离子的运动状态实现了高关联对相干态的运动状态。
Generation of coherent superposition of Fock states in a cavity. Entanglement of atomic coherent states
构造了一种制备相干叠加电磁场Fock态的方案。利用腔场与四能级原子的强相互作用，在腔内产生叠加态。我们证明了仅仅通过改变光场的相对延迟就可以产生所需的任意叠加的腔Fock态的可能性。然后，作为我们模型的另一个应用，我们研究了使用与腔场和激光场的不同相互作用序列来产生中性四能级原子纠缠的方法。
A simple framework for Dirac spinors is developed that parametrizes admissible quantum dynamics and also analytically constructs electromagnetic fields, obeying Maxwell's equations, which yield a desired evolution. In particular, we show how to achieve dispersionless rotation and translation of wave packets. Additionally, this formalism can handle control interactions beyond electromagnetic. This work reveals unexpected flexibility of the Dirac equation for control applications, which may open new prospects for quantum technologies.
Creation of charged massless fermion pair by a photon in external constant crossed electromagnetic field is considered. For this we use the expression of elastic scattering amplitude (EAS) of photon in the one-loop approximation of massive quantum electrodynamics obtained earlier and calculate its massless limit. We assume that the imaginary part of EAS of photon describes the total probability of charged massless fermion pair creation in external electromagnetic field. Photon emission by a charged massless fermion is also studied in constant crossed electromagnetic field. We obtain the total …
Schwinger pair production in some of space-dependent electromagnetic fields is studied analytically by using worldline instantons formalism for scalar quantum electrodynamics. With the increase of the modified Keldysh parameter $γ_{keb}$, the pair production rate decreases, the region of instanton paths expands regardless of the electromagnetic field form. We also find that all of the paths of the instantons for various electromagnetic fields are exactly in the same plane while with the different elliptical shapes. Moreover, the magnitudes of the normalized instantons action with different ext…
Accelerated charges emit electromagnetic radiation. According to classical electrodynamics if the charges move along sufficiently close trajectories they emit coherently, i.e., their emitted energy scales quadratically with their number rather than linearly. By investigating the emission by a two-electron wave packet in the presence of an electromagnetic plane wave within strong-field QED, we show that quantum effects deteriorate the coherence predicted by classical electrodynamics even if the typical quantum nonlinearity parameter of the system is much smaller than unity. We explain this resu…
We consider the electromagnetic field generated by a coherent conductor in which electron transport is described quantum mechanically. We obtain an input-output relation linking the quantum current in the conductor to the measured electromagnetic field. This allows us to compute the outcome of measurements on the field in terms of the statistical properties of the current. We moreover show how under ac-bias the conductor acts as a tunable medium for the field, allowing for the generation of single- and two-mode squeezing through fermionic reservoir engineering. These results explain the recent…
Coulomb impurities in graphene driven by ultrashort electromagnetic pulses: Excitation, ionization, and pair creation
本研究针对带隙单层石墨烯中带电杂质形成的二维人工相对论性原子，建立超短电磁脉冲诱导电子跃迁的理论，借助非微扰骤扰近似推导并分析了激发、电离及电子-空穴对产生概率的解析表达式。
Quantum metamaterials: Electromagnetic waves in a Josephson qubit line
我们考虑经典电磁波通过传输线的传播，传输线由超导谐振器中的相同超导电荷量子比特形成。由于量子位可以在量子态的相干叠加，我们表明，这样的系统表现出有趣的新效果，如一个"呼吸"的光子晶体与振荡带隙，和"量子阿基米德螺旋"的传输，在任意控制的速度，约瑟夫森等离子体波通过传输线。这些效应的关键成分是约瑟夫森传输线的光学性质由量子比特的量子相干态控制。
Coherent Driving of a Quantum System with Modulated Free-Space Electrons
本研究实验证明空间调制自由空间电子束的电磁近场可驱动自旋系统，实现自由电子与束缚电子的共振相互作用，直接观察到电子束近场与自旋态的相位相干耦合，为纳米技术先进光谱工具提供新可能。
Non-canonical quantization of electromagnetic fields and the meaning of $Z_3$
非正则量子化基于正则对易关系的某些可约表示。介绍了电磁非正则量子场的相对论形式。显式地给出了庞加莱群在场和态水平上的酉表示。介绍了多光子和相干态。在适当定义的热力学极限下，相干态光子的统计是泊松分布。构造了具有正确的$S$矩阵的辐射场。$S$矩阵由非正则相干态位移算符给出，这是一个自动消除红外灾难的事实。这一点，加上早期的结果消除真空和紫外线无限，表明非正则量子化导致有限场论。重整化常数$Z_3$是与非正则真空的波函数有关的参数。
Coherent States of Non-Null Torus Knots
本文研究非零纽结经典解对应的量子电磁场相干态，推导位移算符并验证相干态性质，计算场期望值、能量密度等可观测量，建立真空拓扑电磁系统的量子-经典对应。
Coherent shift of localized bound pair in Bose Hubbard model
基于Bethe近似的精确结果，证明了具有任意在位相互作用U的玻色哈伯德模型中存在稳定的束缚对波包.在大U区，发现入射的单粒子可以相干地通过BP波包，并在波包的位置上产生相干位移，从而提出了一种构造BP电荷量子比特的简单方案，实现了在一维波导中控制一个且仅一个光子相干输运的量子开关.
The pair coherent state is a state of a two-mode radiation field which is known as a state with non-Gaussian wave function. In this paper, the upper and lower bounds for D-concurrence (a new entanglement measure) have been studied over this state and calculated.
Covariant Wave Function Reduction and Coherent Decays of Kaon Pair
最近发展的相对论协变公式的波函数减少说明Lipkin的建议，研究CP破坏的相干衰变的K介子对。协变的结果与文献中提出的幅度方法一致。
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