High Intensity Generation of Entangled Photons in a Two‐Mode Electromagnetic Field

At present, the sources of entangled photons have a low rate of photon generation. This limitation is a key component of quantum informatics for the realization of such functions as linear quantum computation and quantum teleportation. In this paper, we propose a method for high intensity generation of entangled photons in a two‐mode electromagnetic field. On the basis of exact solutions of the Schrödinger equation, when electrons interact in an atom with a strong two‐mode electromagnetic field, it is shown that there may be large quantum entanglement between photons. The quantum entanglement is analyzed on the basis of the Schmidt parameter. It is shown that the Schmidt parameter can reach very high values depending on the choice of characteristics of the two‐mode fields. We find the Wigner function for the considered case. Violation of Bell's inequalities for continuous variables is demonstrated.     

量子化电磁场中的非经典电子波包:电子与光子的纠缠

文中研究了量子化电磁场中非经典电子波包的运动。当初始光子态是Fock态时，随着电子和光子所组成系统的演化，初台可分离的电子态和光子态会互相纠缠，而且电子几率密度的时间演化呈非经典的分岔和汇合的现象。基到这些非经典特征，电子可以在光子场中被加速和减速，而系统保持能量守恒。     

Excitation of the Classical Electromagnetic Field in a Cavity Containing a Thin Slab with a Time-Dependent Conductivity

We derive an exact infinite set of coupled ordinary differential equations describing the evolution of the modes of the classical electromagnetic field inside an ideal cavity containing a thin slab with the time-dependent conductivity σ(t) and dielectric permittivity ε(t) for the dispersion-less media. We analyze this problem in connection with the attempts to simulate the so-called dynamical Casimir effect in three-dimensional electromagnetic cavities containing a thin semiconductor slab periodically illuminated by strong laser pulses. Therefore, we assume that functions σ(t) and δε(t) = ε(t) ? ε(0) are different from zero during short time intervals (pulses) only. Our main goal here is to find the conditions under which the initial nonzero classical field could be amplified after a single pulse (or a series of pulses). We obtain approximate solutions to the dynamical equations in the cases of “small” and “big” maximal values of the functions σ(t) and δε(t). We show that the single-mode approximation used in the previous studies can be justified in the case of “small” perturbations, but the initially excited field mode cannot be amplified in this case if the laser pulses generate free carriers inside the slab. The amplification could be possible, in principle, for extremely high maximum values of conductivity and the concentration of free carries (the model of an “almost ideal conductor”) created inside the slab under the crucial condition providing the negativity of the function δε(t). This result follows from a simple approximate analytical solution confirmed by exact numerical calculations. However, the evaluation shows that the necessary energy of laser pulses must be, probably, unrealistically high.     

On the Gauge Invariance of the Transition Probability of a Charged Particle in Electromagnetic Field

This paper suggests a principle to find a unitary operator U which transforms non-physical quantity,zero-potential Hamiltonian Ho, into true physical quantity UHoU for a charged particle in classical electromagneticfield, and puts forward a unified form of constructing gauge-independent transition probabilities in this case. Differentmethods correspond to different unitary operators which satisfy the above-mentioned principle.     

On the Mean Field and Classical Limits of Quantum Mechanics

The main result in this paper is a new inequality bearing on solutions of the N-body linear Schrödinger equation and of the mean field Hartree equation. This inequality implies that the mean field limit of the quantum mechanics of N identical particles is uniform in the classical limit and provides a quantitative estimate of the quality of the approximation. This result applies to the case of C^1,1 interaction potentials. The quantity measuring the approximation of the N-body quantum dynamics by its mean field limit is analogous to the Monge–Kantorovich (or Wasserstein) distance with exponent 2. The inequality satisfied by this quantity is reminiscent of the work of Dobrushin on the mean field limit in classical mechanics [Func. Anal. Appl. 13, 115–123, (1979)]. Our approach to this problem is based on a direct analysis of the N-particle Liouville equation, and avoids using techniques based on the BBGKY hierarchy or on second quantization.     

等时间间隔内光子数奇偶随机性的光量子随机源

提出一种基于等时间间隔内光子数奇偶随机性光量子随机源.将连续波激光二极管发射的光衰减成离散的单光子序列,利用雪崩光电二极管单光子探测模块来探测光子,通过测量等时间内探测到光子数的奇偶性来提取随机位.研制出了基于现场可编程门阵列的随机位提取电路,测试和分析了时间间隔大小和单光子计数模块的性能参量对所设计随机源提取随机数性能的影响.根据系统平均计数率自动设置时间间隔大小,实现了偏差小、速度快的随机位产生器.所设计随机源工作在计数率为20 Mcps,时间间隔设置为0.5μs时,可获得2 Mbit/s的随机位产生速率.运用随机性检测包ENT和STS对所获得的随机位序列进行测试,表明序列的随机性满足真随机数标准,不需要后续处理.     

Classical Quarks in Dual Electromagnetic Fields

Electromagnetic properties of quark-like particles are examined in a classical field model involving extended dual electromagnetic fields. These can have fractional charges and a confining potential that derives essentially completely from a short-range weaker potential. The combined potentials exhibit an asymptotically free spherical surface and contribute to the masses of the particles. The quarks are shown to have an intrinsic symmetry that describes their structures in hadrons. Multi-quark solutions are easily obtained for both stable and unstable particles. Each quark can undergo simple harmonic motion in a range of frequencies.     

Partially Classical States of a Boson Field

Employing positive-definiteness arguments we analyse Boson field states, which combine classical and quantum mechanical features (signal and noise), in a constructive manner. Mathematically, they constitute Bauer simplexes within the convex, weak-*-compact state space of the C*-Weyl algebra, defined by a presymplectic test function space (smooth one-Boson wave functions) and are affinely homeomorphic to a state space of a classical field. The regular elements are expressed in terms of weak distributions (probability premeasures) on the dual test function space. The Bauer simplex arising from the bare vacuum is shown to generalize the quantum optical photon field states with positive P-functions.     

Regular Electric Field in Electromagnetic Coupled to a Scalar Field

In the framework of an electromagnetic field coupled nonminimally with a scalar field in flat spacetime, the existence of a non-singular electric field is proved for a point electric charge or electric monopole. In analogy with the Maxwell-dilaton system introduced by Gibbons and Wells, first, a Maxwell-anti-dilaton system is constructed where the radial electric field of a static electric monopole is coupled to an anti-dilaton. The field equations are solved analytically for the electric and dilaton fields and observe the nonsingular electric field. Also, the self-energy of the electric monopole is found to be finite. Furthermore, the formalism to a Maxwell-scalar field is generalized where a mechanism is introduced upon which the coupled regular-electric field and scalar field is obtained. The formalism shows that for a given regular electric field there are two supersymmetric coupling functions corresponding to a scalar and a phantom field.     

On Cluster Properties of Classical Ferromagnets in an External Magnetic Field

Correlation functions of ferromagnetic spin systems satisfying a Lee-Yang property are studied. It is shown that, for classical systems in a non-vanishing uniform external magnetic field h, the connected correlation functions decay exponentially in the distances between the spins, i.e., the inverse correlation length (“mass gap”), m(h), is strictly positive. Our proof is very short and transparent and is valid for complex values of the external magnetic field h, provided that \(\mathrm {Re}\, h \not = 0\). It implies a mean-field lower bound on m(h), as \(h \searrow 0\), first established by Lebowitz and Penrose for the Ising model. Our arguments also apply to some quantum spin systems.     

双模压缩场与V型原子相互作用光场的性质

研究了双模压缩真空场与V型三能级运动原子的相互作用,得到光场二阶相干度和模间相干度的解析表达式;通过数值计算分析了原子运动速度、场模结构参数和平均光子数对光场二阶相干度和模间相干度的影响.结果表明:平均光子数的增加使得二阶相干度和模间相干度显著增大;而原子运动速度、模场结构参数的增加虽然对光子聚束效应和反聚束效应的强度影响不大,却使其演化周期大大减小.     

Anisotropic Harmonic Oscillator in a Static Electromagnetic Field

A nonrelativistic charged particle moving in an anisotropic harmonic oscillator potential plus a homogeneousstatic electromagnetic field is studied. Several configurations of the electromagnetic field are considered. The Schrodingerequation is solved analytically in most of the cases. The energy levels and wave functions are obtained explicitly. Insome of the cases, the ground state obtained is not a minimum wave packet, though it is of the Gaussian type. Coherentand squeezed states and their time evolution axe discussed in detail.     

A Simulation of Near Field Optics by Three Dimensional Volume Integral Equation of Classical Electromagnetic Theory

A numerical simulation code for three dimensional problems of near-field optics has been developed using the volume integral equation with the moment method. The object is assumed to be continuous and macroscopic dielectric and can be treated by macroscopic Maxwell#x0027;s equations. The code can treat the large-scale moment method matrix that is obtained by the discretization of the volume integral equation. The resultant matrix equation is solved by an iteration method called the generalized minimum residual method with reasonable computational cost for simple problems of near field optics. Simulation of a simplified model of a scanning near-field optical microscope has been performed and basic polarization characteristics of the system have been investigated in detail. The code is also applied to the collection-mode of a photon scanning tunneling microscope, where the incident wave is the evanescent wave, and basic relation between near-field and far field i.e., output image, is recognized.     

Vacuum Birefringence in a Field of a Plane Electromagnetic Wave

Optics and Spectroscopy - The process of vacuum birefringence in a strong electromagnetic field is investigated, in which a probe photon changes its polarization when passing through a...     

Non-Wiener Dynamics of Open Systems for Nonzero Number Density of Surrounding Photons

Journal of Experimental and Theoretical Physics - We propose a collective decay model for a localized ensemble of identical atoms in a vacuum broadband electromagnetic field with a nonzero photon...     

Anisotropic Harmonic Oscillator in a Static Electromagnetic Field

A nonrelativistic charged particle moving in an anisotropic harmonic oscillator potential plus a homogeneous static electromagnetic field is studied. Several configurations of the electromagnetic field are considered. The Schrödinger equation is solved analytically in most of the cases. The energy levels and wave functions are obtained explicitly. In some of the cases, the ground state obtained is not a minimum wave packet, though it is of the Gaussian type. Coherent and squeezed states and their time evolution are discussed in detail.