Influence of the virtual photon field on the squeezing properties of atom laser

This paper investigates the squeezing properties of an atom laser without rotating-wave approximation in the system of a binomial states field interacting with a two-level atomic Bose--Einstein condensate. It discusses the influences of atomic eigenfrequency, the interaction intensity between the optical field and atoms,parameter of the binomial states field and virtual photon field on the squeezing properties. The results show that two quadrature components of an atom laser can be squeezed periodically. The duration and the degree of squeezing an atom laser have something to do with the atomic eigenfrequency and the parameter of the binomial states field, respectively. The collapse and revival frequency of atom laser fluctuation depends on the interaction intensity between the optical field and atoms. The effect of the virtual photon field deepens the depth of squeezing an atom laser.     

虚光场效应对原子激光压缩性质的影响

在压缩真空态光场和二能级原子玻色-爱因斯坦凝聚体相互作用系统中, 应用全量子理论, 分别在旋波近似和非旋波近似下, 研究了原子激光的压缩特性以及原子本征频率、光场-原子的耦合系数、光场初始压缩因子以及虚光场对原子激光压缩特性的影响. 研究表明,原子激光的两个正交分量均可被周期性压缩,原子的本征频率决定了原子激光两个正交分量涨落的量子Rabi频率,光场与原子的耦合系数决定了原子激光正交分量涨落的崩塌-回复振荡频率,当光场初始压缩因子增大和考虑虚光场效应时,原子激光正交分量的压缩深度均加深. 关键词： 玻色-爱因斯坦凝聚 压缩真空态 原子激光 虚光场效应     

Entropy and variance squeezing of two coupled modes interacting with a two-level atom: Frequency converter type

A modified Jaynes-Cummings model which consists of a two-level atom interacting with two modes of the electromagnetic field is introduced. More precisely we have considered a Hamiltonian model that includes two types of interaction: One is the field-field (frequency converter type) and the other is the atom-field interaction. By invoking a canonical transformation an exact solution of the wave function in the Schrödinger picture is obtained. The result presented in this context is used to discuss the atomic inversion as well as the entropy squeezing and variance squeezing phenomena. We have shown that the existence of the second field coupling parameter reduces the amount of squeezing in all quadratures, while the effect of the detuning parameter would lead to the superstructure phenomenon which becomes more pronounced upon increasing the mean photon numbers, in the states which are taken to be converter states.     

Revival‐collapse phenomenon in the quadrature squeezing of the multiphoton Jaynes‐Cummings model with the binomial states

In this paper we study the interaction between a two‐level atom and a quantized single‐mode field, namely, the Jaynes‐Cummings model (JCM). The field and the atom are initially prepared in the binomial state and the excited atomic state, respectively. For this system we prove that the revival‐collapse phenomenon exhibited in the atomic inversion of the standard JCM can be numerically (naturally) manifested in the evolution of the squeezing factor of the three‐photon (standard) JCM provided that the initial photon‐number distribution of the radiation field has a smooth envelope.     

Two-photon resonance fluorescence

The excitation spectrum of a two-level atom interacting with a strong electromagnetic field is considered when the atomic transition frequency is nearly twice the frequency of the laser field. The spectral function consists of four Lorentzian lines describing: the central line peaked near the two-photon resonance, two sidebands peaked at the high and low frequency regions respectively and the one-photon frequency mode. In the limit of high photon densities, the low frequency photon mode is induced by the pump field which removes the singularity occurring at the two-photon resonance frequency.     

虚光场对光场与玻色-爱因斯坦凝聚体相互作用系统中光场压缩性质的影响

在压缩真空态光场和二能级原子玻色-爱因斯坦凝聚体相互作用系统中, 应用全量子理论, 采用非旋波近似, 研究了光场的压缩特性以及原子本征频率、原子-光场的耦合系数、光场初始压缩因子以及虚光场对系统光场压缩特性的影响. 研究表明, 光场的两个正交分量均被周期性压缩, 其压缩深度与光场初始压缩因子有关, 光场与原子的耦合系数决定了光场的量子崩塌-回复频率,虚光场效应使得光场的压缩深度增强.     

Influence of a Classical Homogeneous Gravitational Field on Dissipative Dynamics of the Phase Damped Jaynes–Cummings Model under the Markovian Approximation

In this paper, we study the dissipative dynamics of the phase damped Jaynes–Cummings model under the Markovian approximation in the presence of a classical homogeneous gravitational field. The model consists of a moving two-level atom simultaneously exposed to the gravitational field and a single-mode traveling radiation field in the presence of a phase damping mechanism. We first present the master equation for the reduced density operator of the system under the Markovian approximation in terms of a Hamiltonian describing the atom-field interaction in the presence of a homogeneous gravitational field. Then, by making use of the super-operator technique, we obtain an exact solution of the master equation. Assuming that initially the radiation field is prepared in a Glauber coherent state and the two-level atom is in the excited state, we investigate the influence of gravity on the temporal evolution of collapses and revivals of the atomic population inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting statistics and quadrature squeezing of the radiation field in the presence of phase damping.     

Quantum Mechanics of Two-Field Parametric Frequency Converter Interacting with a Single Atom

In this communication we deal with a new model Hamiltonian representing the interaction between a two-level atom and two electromagnetic field modes in a cavity. The interaction between the modes has been taken into account and considered to be of a parametric frequency converter type. The model can be regarded as a generalization of two different systems: the Jaynes–Cummings model (atom–field interaction) and the two-mode frequency converter model (field–field interaction). Under a certain condition an exact solution for the equations of motion in the Heisenberg picture is given. The wavefunction in the Schrödinger picture is also constructed and used to discuss some statistical properties related to the model. We assume that the fields are initially in coherent states. We discuss atomic inversion, photon number distribution, squeezing and other phenomena. We show in all cases that the system is very sensitive to any variation in the mean photon numbers.     

压缩态光场变耦合系数双光子J-C模型性质

讨论了初始光场为压缩态、原子-光场耦合系数随时间变化情形下双光子过程J-C模型的量子统计性质。具体研究了双光子过程中原子布居数反转、光场的压缩等随时间的演化性质,讨论了初始光场的压缩系数、压缩相位及耦合系数变化快慢对这些性质的影响。研究结果表明,初始光场的压缩系数增大,崩塌和回复的频率增大,回复值减小。当原子-光场耦合系数变化缓慢时,崩塌和回复现象被延迟。而光场逐渐失去压缩性质;而当耦合系数变化较快时,崩塌和回复现象被加速,而光场压缩量将产生振荡,压缩效应将反复出现。     

非线性光子晶体中原子辐射光场的非经典性质

讨论了非线性光子晶体微腔中二能级原子在相干场驱动下腔场的频谱特性及光子的统计性质.研究结果表明,当光子晶体的态密度很大时,如果腔场模与原子共振荧光Mollow峰的中心峰共振,则腔场的涨落压缩到量子散弹噪声之下,且与线性光子晶体微腔的情况相比其谱线峰值变大.当驱动场频率较大时光子服从亚Poisson分布,且非常接近Poisson分布. 关键词： 光子晶体 参量振荡 非弹性谱 二阶相关函数     

非线性光子晶体中原子辐射光场的非经典性质

讨论了非线性光子晶体微腔中二能级原子在相干场驱动下腔场的频谱特性及光子的统计性质.研究结果表明,当光子晶体的态密度很大时,如果腔场模与原子共振荧光Mollow峰的中心峰共振,则腔场的涨落压缩到量子散弹噪声之下,且与线性光子晶体微腔的情况相比其谱线峰值变大.当驱动场频率较大时光子服从亚Poisson分布,且非常接近Poisson分布.     

The squeezing properties in the Jaynes-Cummings model with arbitrary intensity-dependent coupling

Summary We have studied the squeezing properties of the atom and the radiation field in arbitrary intensity-dependent-coupling Jaynes-Cummings model when it is restricted to the following initial condition: the atom in its coherent state and the field in the vacuum state. The influence of virtual-photon processes on the atomic squeezing predicted by the Jaynes-Cummings model (JCM) has been examined. The relationship between the field and atomic squeezing in the resonant multi-photon JCM has been discussed. The symmetry between the field and atomic squeezing (SFAS) has been exposed in the resonant vacuum one-photon JCM, and the influence of non-resonant interaction and virtual-photon processes on the SFAS has also been discussed.     

Entropy squeezing of an atom with a k-photon in the Jaynes--Cummings model

The entropy squeezing of an atom with a k-photon in the Jaynes-Cummings model is investigated. For comparison, we also study the corresponding variance squeezing and atomic inversion. Analytical results show that entropy squeezing is preferable to variance squeezing for zero atomic inversion. Moreover, for initial conditions of the system the relation between squeezing and photon transition number is also discussed. This provides a theoretical approach to finding out the optimal entropy squeezing.     

频率变化场与原子相互作用系统中原子的信息熵压缩

利用J-C模型,考虑场频率随时间以正弦函数形式作小量变化,在旋波近似下,研究了二能级原子与单模辐射场相互作用系统中原子的信息熵压缩特性.利用数值计算方法给出原子的信息熵压缩因子随时间的演化曲线.研究结果表明:原子的信息熵仅在演化的初期呈现压缩效应,初始的原子分布角、光场强度和场频率随时间的变化对原子的信息熵压缩有明显影响.场频率随时间的变化对原子的信息熵压缩因子的演化具有调制作用,随场频率变化的幅值增大,调制作用增强,压缩效应减弱.     

动态Stark效应对双光子过程中原子和场的动力学行为的影响

采用单模量子化光场和有效二能级的多能级原子组成的模型,研究了动态Stark效应对该系统原子和压缩态光场的双光子过程动力学行为的影响。动态Stark效应将使原子反转Rabi振荡的再生(revival)幅度降低,周期缩短,原子和场的能量交换加快;也有利于光子反聚束效应加强和亚泊松光子统计分布变窄,但却使光场压缩特性减弱,甚至消失。     

Interactions of a two-level atom and a field with a time-varying frequency without rotating-wave approximation

The interactions between a two-level atom and a field with a time-varying frequency without rotating-wave approximation have been investigated. The frequency of the field varies in the form of rectangle. The dynamic behaviors of the atomic population inversion, photon anti-bunching and atomic dipole squeezing are investigated numerically as function of time. A number of novel phenomena are discovered and discussed.     

非共振Jaynes-Cummings模型中强相干光的长时间挤压行为

利用Jaynes-Cummings(缩写为J-C)模型研究了失谐情况下强相干光的长时间挤压行为,其中原子与光场的作用包括单光子跃迁和双光子跃迁两种情况。给出大N极限下挤压度的解析表达式。研究结果表明:对单光子跃迁,失谐(非共振)时的挤压行为定性上与共振时相似,小的失谐对挤压只有小的影响,双光子跃迁时情况不同,失谐起着重要作用。共振时不出现挤压,失谐时才出现挤压,被压缩的不确定度准周期地出现极小,在大N极限下,此极小值系列并趋于零。     

非共振双光子Jaynes—Cummings模型中原子的偶极压缩

考虑到失谐量和初始原子相干性，研究了双光子Ｊａｙｎｅｓ－Ｃｕｍｍｉｎｇｓ模型中原子的压缩行为。研究表明，失谐量对场－原子相互作用中的原子压缩行为的影响很大，通过数值计算，还讨论了初始平均光子数与原子压缩的关系。     

非共振双光子Jaynes-Cummings模型中原子的偶极压缩

考虑到失谐量和初始原子相干性，研究了双光子Ｊａｙｎｅｓ－Ｃｕｍｍｉｎｇｓ模型中原子的压缩行为。研究表明，失谐量对场－原子相互作用中的原子压缩行为的影响很大。通过数值计算，还讨论了初始平均光子数与原子压缩的关系。     

二项式光场与级联三能级原子在非旋波近似下相互作用的量子特性

利用全量子理论,在非旋波近似下,对与级联型三能级原子相互作用的二项式光场的光场压缩效应和原子布居几率进行了精确求解.讨论了二项式光场参量η对光场压缩效应的影响,同时也讨论了二项式态光场的最大光子数M对原子布居几率的影响.数值计算结果表明:随着二项式光场参量η的增大,光场压缩效应的持续时间先增大后减小.在非旋波近似下,由于虚光子的影响,光场压缩效应的演化曲线出现了"小锯齿状"的振荡;随着二项式光场的最大光子数M的增大,原子布居几率回复塌缩周期逐渐增大,并且原子布居几率在塌缩区不能完全塌缩,而是出现了"小锯齿状"的振荡.另外文中也讨论了非旋波项对系统量子特性的影响.