Atomic Coherent State,Entangled State and Phase Operator for Studying Interference Between Two Bose-Einstein Condensates

For studying the interference between two Bose-Einstein condensates we introduce the atomic coherentstate(ACS)in the Schwinger bosonic realization along with the phase operator to directly calculate the interferencepattern with steady relative phase cos φ.Eigenstates of the density operator of condensates are classified as A CS is alsodemonstrated.The entangled state representation is used in some calculations.

Measuring gravitational effect of superintense laser by spin-squeezed Bose-Einstein condensates interferometer

We consider an extremely intense laser,enclosed by an atom interferometer.The gravitational potential generated from the high-intensity laser is solved from the Einstein field equation under the Newtonian limit.We compute the strength of the gravitational force and study the feasibility of measuring the force by the atom interferometer.The intense laser field from the laser pulse can induce a phase change in the interferometer with Bose-Einstein condensates.We push up the sensitivity limit of the interferometer with Bose-Einstein condensates by spin-squeezing effect and determine the sensitivity gap for measuring the gravitational effect from intense laser by atom interferometer.

Quantum Statistical Behaviors of Interaction of an Atomic Bose-Einstein Condensate with Laser

We have investigated quantum statistical behaviors of photons and atoms in interaction of an atomic Bose Einstein condensate with quantized laser field. When the quantized laser field is initially prepared in a superposition state which exhibits holes in its photon-number distribution, while the atomic field is initially in a Fock state, it is found that there is energy exchange between photons and atoms. For the input and output states, the photons and atoms may exhibit the sub-Poissonian distribution. The input and output laser fields may exhibit quadrature squeezing, but for the atomic field, only the output state exhibits quadrature squeezing. It is shown that there exists the violation of the Cauchy-Schwartz inequality, which means that the correlation between photons and atoms is nonclassical.

Optomechanical Schrödinger cat states in a cavity Bose-Einstein condensate

Schrödinger cat states,consisting of superpositions of macroscopically distinct states,provide key resources for a large number of emerging quantum technologies in quantum information processing.Here we propose how to generate and manipulate mechanical and optical Schrödinger cat states with distinguishable superposition components by exploiting the unique properties of cavity optomechanical systems based on Bose-Einstein condensate.Specifically,we show that in comparison with its solid-state counterparts,almost a 3 order of magnitude enhancement in the size of the mechanical Schrödinger cat state could be achieved,characterizing a much smaller overlap between its two superposed coherent-state components.By exploiting this generated cat state,we further show how to engineer the quadrature squeezing of the mechanical mode.Besides,we also provide an efficient method to create multicomponent optical Schrödinger cat states in our proposed scheme.Our work opens up a new way to achieve nonclassical states of massive objects,facilitating the development of fault-tolerant quantum processors and sensors.

Influence of the virtual photon field on the squeezing properties of an 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.

One-dimensional atom laser in microgravity

Using coupled Gross–Pitaevksii(GP)equations,we simulate the output of one-dimensional pulsed atom laser in space station.We get two atom laser pulses propagating in opposite directions with one pulsed RF coupling.Compared with atom laser under gravity,the laser pulse in microgravity shows much slower moving speed,which is suitable to be used for long-term investigations.We also simulate the output flux at different coupling strengths.

Model for Interaction Between Photon and Cold Atom in QED Cavity

A model has been established for the interaction between a single-mode optical field and a 2-energy-level cold atom with exact analytic solutions given. The processes of momentum and energy exchanges between the optical field and the cold atom due to the interaction between them are discussed in detail, and a formula has been given for the variation of momentum and energy exchange volumes with time t in dress state while both the effects of photon recoil and Doppler effect are taken into consideration.

原子间相互作用对V型三能级原子激光压缩性质的影响

研究了V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统中原子激光的两个正交分量的压缩性质,并与Ξ型三能级原子玻色-爱因斯坦凝聚体和双摸压缩相干态相互作用系中原子激光的压缩作了比较.结果表明:压缩相干态光场的初始压缩因子和凝聚体中原子间的相互作用强度对原子激光的两个正交分量的压缩有明显的影响,随光场压缩因子增大原子激光的压缩深度增加,而随原子间相互作用变强,对原子激光的正交分量的压缩的影响变浅.

原子BEC与二项式光场系统的压缩性质

利用格子液体方法改进了二能级原子玻色-爱因斯坦凝聚与二项式光场相互作用系统的哈密顿量,并且对系统中原子激光的压缩性质进行了研究。结果表明,原子激光具有量子Rabi振荡现象,且被周期性压缩,其量子Rabi振荡频率和最大压缩深度主要依赖于光场和原子间的相互作用强度。

玻色-爱因斯坦凝聚与二项式光场相互作用系统中的压缩特性

根据二能级原子玻色-爱因斯坦凝聚体与二项式光场耦合系统的相互作用特点,研究了二项式光场和玻色-爱因斯坦凝聚系统的耦合输出相干原子束的压缩性质.结果表明:光场的两正交分量的涨落均可压缩,压缩程度受系统参数的影响,并且随时间呈周期性变化;原子激光的两正交分量的涨落也均可压缩,改变光场与原子间的相互作用强度时,原子间的相互作用不利于原子激光压缩效应的产生,若考虑存在外场作用,则外场对压缩效应将产生明显的影响.

利用V型三能级原子玻色-爱因斯坦凝聚体与双模压缩光场相互作用制备双模原子激光

研究了V型三能级原子的玻色-爱因斯坦凝聚体(BEC)与双模压缩相干态光场相互作用系统的量子动力学行为,分析了利用V型三能级原子BEC与双模压缩相干态光场相互作用制备双模原子激光的可能性。结果表明:在光场作用下,V型三能级原子BEC中被激发到非俘获态的原子,仍保持其相干态的特性,从而在理论上证明了利用V型三能级原子BEC与双模压缩相干态光场相互作用可以产生双模原子激光.

玻色-爱因斯坦凝聚原子与Schrdinger猫态相互作用系统中的压缩特性

利用全量子理论,研究了玻色-爱因斯坦凝聚原子与Schrdinger猫态相互作用系统中,光场和原子激光的压缩特性。结果表明:在系统中,偶相干态、奇相态分别与玻色-爱因斯坦凝聚原子相互作用,偶相干态、奇相态光场和原子激光均不呈现压缩效应。而Yurke-Stoler相干态光场和原子激光呈现压缩效应。在强场(|α|=1)情况下,三种不同光场的两种压缩现象均不产生。光场和原子激光的压缩特性主要受初始光强和耦合常数的影响。

多能级原子系统暗压缩态的制备

基于二能级原子暗压缩态的制备方案,对多能级原子系统暗压缩态的产生机理进行研究,并提出一个如何在多能级原子系统中制备压缩态的方案。结果表明,在Lamb-Dicke近似下,考虑边带冷却效应就可以将多能级原子冷却至最低最子态;通过选择合适的入射光中心频率,利用多能级原子系统同样可以激光冷却被俘获的原子,并导致暗压缩态的出现。

原子间相互作用对原子激光压缩性质的影响

研究了原子间相互作用对光场与原子玻色 爱因斯坦凝聚体相互作用系统中耦合输出的相干原子束压缩性质的影响 .结果表明 :原子激光的两正交分量的涨落均可压缩 ,玻色 -爱因斯坦凝聚体中原子间的相互作用不利于原子激光的压缩 .

原子间相互作用对光场和原子激光压缩性质的影响

对文献中给出的光场与二能级原子玻色-爱因斯坦凝聚体(BEC)相互作用系统的哈密顿量进行分析,表明文献中对原子间相互作用部分的处理有不合理之处,文献中的处理过高估计了原子间相互作用的贡献,从而对该哈密顿量作出了改进.用改进的哈密顿量解析地求解了非旋波近似下光子和原子算符的运动方程,并结合BEC的有关实验条件对哈密顿量中的有关参数作出了估计,研究了光场与原子玻色-爱因斯坦凝聚体相互作用系统中,光场和耦合输出相干原子束的压缩性质.结果表明:光场两正交分量的涨落均随时间按余弦规律周期性地变化,原子激光的两正交分量的涨落均可压缩.

原子间相互作用对双模原子激光压缩性质的影响

研究了由单模压缩相干态光场与Ξ型三能级原子玻色爱因斯坦凝聚体(BEC)相互作用系统中耦合输出的双模原子激光的压缩特性,重点讨论了玻色爱因斯坦凝聚体原子间相互作用对原子激光压缩性质的影响,并讨论了原子激光压缩对光场初始压缩因子的依赖关系。结果表明:由光场诱导的双模原子激光呈现周期性的压缩,原子间的相互作用和光场初始压缩因子对原子的压缩性质具有重要影响。原子间的相互作用影响原子激光压缩的振荡频率而不会影响其压缩深度,而初始光场的压缩因子则对原子激光压缩深度产生调制作用,且初始光场的压缩因子越大,则原子激光压缩的时间越短。

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.

V型三能级原子双模光场系统中光场压缩性质

本文利用格子液体方法对文献中给出的V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统的哈密顿量进行分析,发现文献中对原子间相互作用部分的处理有不合理之处,从而对该哈密顿量作出了改进并研究了V型三能级原子双模光场系统中光场压缩性质.结果表明:光场两正交分量交替呈现周期性压缩现象,其压缩深度与光场初始压缩因子密切相关,而压缩时间与双模光场的频率有关.

■型三能级原子玻色-爱因斯坦凝聚体对光场压缩性质的影响

利用格子液体方法对■型三能级原子玻色-爱因斯坦凝聚体与单模压缩相干态光场相互作用系统的哈密顿量进行了改进,并且研究了■型三能级原子单模光场系统中光场压缩性质.结果表明:光场两正交分量交替呈现周期性压缩,其最大压缩深度由光场与原子间的相互作用强度和光场初始压缩因子决定,而压缩时间与光场的圆频率有关.

二能级原子玻色-爱因斯坦凝聚体与双模光场相互作用系统中原子激光的压缩性质

利用格子液体方法对二能级原子玻色-爱因斯坦凝聚体与双模光场相互作用系统的哈密顿量进行了改进,并且研究了系统中原子激光的压缩性质.结果表明:原子激光的两个正交分量均可被周期性压缩,其最大压缩深度主要依赖于光场初始压缩因子,而崩塌-回复振荡频率和量子Rabi振荡频率主要分别由光场与原子间的相互作用强度和光场圆频率决定.