Quantum theory of coherent anti-Stokes Raman scattering in an inhomogeneously broadened gaseous system

A quantum-statistical treatment of coherert anti-Stokes Raman scatterirg in a gaseous system is presented. The atomic system is described by two energy levels. Both the atomic system and the radiation fields are quartized. The effects of atomic motion ard the detuning are incorporated into the analysis. The equations of motion describing the photor statistics of pump, Stokes and anti-Stokes fields are obtained considering the process as a two-step one. The time-evolution of average photon number and the second-order coherence of the anti-Stokes fields for different initial distributions are studied. The occurrence of antibunching is investigated.     

Noise correlations in a doubly-resonant atomic optical parametric oscillator

The simultaneous generations of bright Stokes and anti-Stokes fields are realized by using only one pump field in a Doppler-broadened atomic medium confined in an optical ring cavity. A vacuum-induced absorption phenomenon is also observed in such a system. By utilizing an external Fabry-Perot cavity to separate the Stokes and anti-Stokes fields, we investigate the noise correlation and anticorrelation properties between the Stokes, anti-Stokes, and the pump fields.     

Quantum-statistics of stimulated hyper-Raman scattering in an inhomogeneously broadened system under three-photon resonance condition

A fully quantum mechanical density-matrix formalism of stimulated hyper-Raman scattering is presented. The effects of atomic motion, higher-order non-linearities and losses are included. The equations are solved exactly under the three-photon resonance condition and a situation of low losses. The photon-statistics of the Stokes field is studied in the steady-state. The coherence characteristics are studied.     

On the quantum theory of stimulated Raman scattering

A fully quantum mechanical density-matrix formalism of stimulated Raman scattering is presented. The effects of atomic motion, non-linear parameters and loss are included. The equations are solved to fourth-order in atom-field coupling constant. The steady-state Stokes-photon distribution is studied. A study of an approximate time-dependent case is also discussed. The results show that only a fraction of incident pump photons can be converted to Stokes photons.     

On the quantum theory of stimulated Raman scattering II: Effect of detuning and upper-level population

A fully quantum mechanical density-matrix formalism of stimulated Raman scattering is presented with the help of the usual two-level atomic (molecular) system. Detuning between the frequencies involved is taken into account. Both the atomic levels are considered to be populated initially. The equations are solved to fourth-order in atom-field coupling constant and various aspects of photon-statistics of Stokes field are studied. The coherence characteristics of Stokes field are obtained and an approximate time-dependent case discussed.     

Preparation and control of entangled states in the two-mode coherent fields interacting with a moving atom via two-photon process

We investigate the preparation and the control of entangled states in a system with the two-mode coherent fields interacting with a moving two-level atom via the two-photon transition. We discuss entanglement properties between the two-mode coherent fields and a moving two-level atom by using the quantum reduced entropy, and those between the two-mode coherent fields by using the quantum relative entropy. In addition, we examine the influences of the atomic motion and field-mode structure parameter $p$ on the quantum entanglement of the system. Our results show that the period and the duration of the prepared maximal atom-field entangled states and the frequency of maximal two-mode field entangled states can be controlled, and that a sustained entangled state of the two-mode field, which is independent of atomic motion and the evolution time, can be obtained, by choosing appropriately the parameters of atomic motion, field-mode structure, initial state and interaction time of the system.     

Technique of quantum memory on the basis of a photon echo in gases

The technique of quantum memory based on the use of a photon echo in gases is studied theoretically taking into account three-dimensional specific features in the propagation of light fields and the motion of atoms in a gas. Analytical solutions describing the effects of atomic motion and diffraction of light fields on the properties of the quantum state of light being reconstructed are obtained. Estimates of the parameters of light fields that are optimum for realizing the quantum memory based on a photon echo in gaseous media are presented.     

双模压缩真空态与运动原子相互作用系统的场熵演化特性

利用全量子理论,研究了双模压缩真空场与运动原子相互作用系统的场熵演化特性,讨论了不同初始状态态下原子的运动速度、模场结构对场熵的影响。结果表明,场熵通过时间因子sin2(εpgt/2)度与场模结构参数,原子运动和场模结构引起了附加的“熵振荡”。     

含原子运动的Jaynes-Cummings模型中的量子态保真度

研究了相干光场作用下的含原子运动的Jaynes-Cummings模型中体系量子态保真度,讨论了不同的原子初态条件下,原子的运动和场模结构对体系中的量子态保真度的影响。结果表明：在一定的条件下,原子运动的速度和场模结构参数可调制相互作用体系的量子态保真度。     

Radiative asymptotic behavior of stimulated Raman scattering

This paper uses an integrable model to study an asymptotic solution describing the transformation of energy occurring in stimulated Raman scattering. The model allows for motion of populations and for the nonlinear Stark effect. Initial conditions leading to a radiative solution are discussed. The boundary conditions reflect the injection into the medium of high-power pulses of constant-amplitude pump and Stokes fields. It is shown that the radiative asymptotic behavior of this problem in the limit of weak medium excitation and in the limit of rapidly varying intense fields is determined by the kernels of Marchenko equations that are proportional to functions depending only on a self-similar variable. Analytic solutions are found for these cases. Detailed numerical calculations carried out for weak fields corroborate the analytic results. The role of the soliton part of the continuous spectrum of the problem is also studied. It is found that a high-power soliton of the Stokes field can be generated at the leading edge of a wave packet. Zh. éksp. Teor. Fiz. 115, 1168–1195 (April 1999)     

Stokes identification in an atomic ensemble using a filtering system

Polarization filtering and atomic cell filtering are applied in the identification of Stokes signals in an atomic ensemble, and reduce the noise to a level of 10^ - 5 and 10^ - 4 respectively. Good Stokes signals are then obtained. In this article the two filtering systems and the final Stokes output are presented, and the optimization of the polarization filtering system is highlighted.     

失谐对开放的四能级系统无粒子数反转激光的影响

提出开放的四能级双驱动场无反转激光系统的理论模型,由电偶极和旋转波近似得到其密度矩阵方程,讨论无反转激光产生的物理机制,利用数值计算结果分析探测场和驱动场失谐对系统无反转激光增益和粒子数差的影响.     

Cooperative scattering effect between Stokes and anti-Stokes field stimulated by a stream of atoms

This paper is devoted to the study of the cooperative two-photon scattering processes between two resonator modes stimulated by an excited atomic beam. It has been proved that these collective scattering phenomena between the Stokes and anti-Stokes resonator modes are taking place due to the energy transfer between these fields. The statistical properties of the Stokes and anti-Stokes photons have been described using the photon correlation functions. The numerical solution of this equation describes the statistical transformation of n-Stokes photons into anti-Stokes photons.     

All-optical switching and storage in a four-level tripod-type atomic system

The optical behavior of a four-level tripod-type atomic system in a ring resonator driven by a cavity field and two external coherent fields is studied. It is shown that the atomic response exhibits an ultra-sensitive switch from high absorption to nearly transparency by changing the value of one of the control fields. The optical bistable response can be controlled by means of the external fields. The system can flip from the lower to the upper branch of the hysteresis curve without changing the incident probe. Switching and information storage of a light signal are predicted under appropriate triggering of the auxiliary external optical signals.     

Non-inertial electromagnetic effects in matter. Gyromagnetic effect

Non-inertial electromagnetic effects in matter, i.e. electromagnetic fields created by a non-inertial motion of material bodies, are discussed within the Drude–Lorentz (plasma) model of matter polarization. It is shown that an oscillatory motion of a point-like body, or wavelike motion in an extended body gives rise to electromagnetic fields with the same frequency as the frequency of the original motion, while shock-like movements of a point-like body generate electromagnetic fields with the characteristic (atomic scale) frequency of the bodies. The polarization of a rigid body induced by rotations is discussed in various circumstances. A uniform rotation produces a static electric field in a dielectric and a stationary current (and a static magnetic field) in a conductor. The latter corresponds to the gyromagnetic effect (while the former may be called the gyroelectric effect). Both fields are computed for a sphere and the gyromagnetic coefficient is derived. A non-uniform rotation induces emission of electromagnetic fields. The equations of motion for the polarization are linearized for slight non-uniformities of the angular velocity and solved both for a dielectric and a conducting sphere. The electromagnetic field emitted by a dielectric spherically shaped body in (a slightly) non-uniform rotation has the characteristic (atomic scale) frequency of the body (slightly shifted by the uniform part of the angular frequency). In the same conditions, a conducting sphere emits an electromagnetic field whose frequency is double the uniform part of the angular frequency.     

A General Theory of Non-Abelian Electrodynamics

The general theory of gauge fields is used to develop a theory of electrodynamics in which the fundamental structure is non-Abelian and in which the internal gauge field symmetry is O(3), based on the existence of circular polarization and the third Stokes parameter. The theory is used to provide an explanation for the Sagnac effect with platform at rest and in motion. The Sagnac formula is obtained by considering the platform in motion to be a gauge transformation. The topological phases can be described straightforwardly with non Abelian electrodynamics, which produces a novel magnetic field component for all types of radiation, a component which is proportional to the third Stokes parameter. The theory provides a natural explanation for the inverse Faraday effect without phenomenology.     

Quantum entanglement in the system of a moving V-type three-level atom interacting with the SU（1,1）-related coherent fields

In a system with a moving V-type three-level atom interacting with the SU(1,1)-related coherent fields, we investigate the entanglement between the moving three-level atom and the SU(1,1)-related coherent fields by using the quantum-reduced entropy, and that between the SU(1,1)-related coherent fields by using the quantum relative entropy of entanglement. It is shown that the two kinds of entanglement are dependent on the atomic motion and exhibit the periodic evolution with a period of 2π/p. The maximal atom--field qutrit entanglement state can be prepared, and the entanglement preservation of the SU(1,1)-related coherent fields can be realized in the interacting process via the appropriate selection of system parameters and interaction time.     

利用高阶拉盖尔-高斯横模精确测量法布里-珀罗腔内原子的运动轨迹

研究了冷原子与法布里-珀罗腔内拉盖尔-高斯横模强耦合相互作用体系的透射光谱, 分析了透射光谱与原子在腔中运动轨迹的关系. 结果表明, 与厄米特-高斯横模相比, 拉盖尔-高斯横模的腔场与原子的最大耦合系数几乎不随阶数的增加而变化, 使得探测光谱的对比度受模式阶数的影响较小. 在拉盖尔-高斯横模场分布的圆环边缘附近, 原子运动轨迹的微小偏移会引起透射光谱的很大变化, 因此在这些位置可以实现原子运动轨迹的高精度探测.     

Observation of the Rabi oscillation of light driven by an atomic spin wave

Coherent conversion between a Raman pump field and its Stokes field is observed in a Raman process with a strong atomic spin wave initially prepared by another Raman process operated in the stimulated emission regime. The oscillatory behavior resembles the Rabi oscillation in atomic population in a two-level atomic system driven by a strong light field. The Rabi-like oscillation frequency is found to be related to the strength of the prebuilt atomic spin wave. High conversion efficiency of 40% from the Raman pump field to the Stokes field is recorded and it is independent of the input Raman pump field. This process can act as a photon frequency multiplexer and may find wide applications in quantum information science.     

Coherent polarization driven by external electromagnetic fields

The coherent interaction of the electromagnetic radiation with an ensemble of polarizable, identical particles with two energy levels is investigated in the presence of external electromagnetic fields. The coupled non-linear equations of motion are solved in the stationary regime and in the limit of small coupling constants. It is shown that an external electromagnetic field may induce a macroscopic occupation of both the energy levels of the particles and the corresponding photon states, governed by a long-range order of the quantum phases of the internal motion (polarization) of the particles. A lasing effect is thereby obtained, controlled by the external field. Its main characteristics are estimated for typical atomic matter and atomic nuclei. For atomic matter the effect may be considerable (for usual external fields), while for atomic nuclei the effect is extremely small (practically insignificant), due to the great disparity in the coupling constants. In the absence of the external field, the solution, which is non-analytic in the coupling constant, corresponds to a second-order phase transition (super-radiance), which was previously investigated.