双势阱中利用量子非破坏性测量产生自旋压缩玻色-爱因斯坦凝聚态

Quantum nondemolition measuremen generated spin-squeezed Bose-Einstein condensate confined in a double-well trap

着重探究了如何在双势阱中运用量子非破坏性(Quantum Nondemolition,QND)测量产生一个自旋压缩的原子玻色-爱因斯坦凝聚态(Bose-Einstein Condensate,BEC),其中每个势阱的玻色-爱因斯坦凝聚都是由马赫-曾德干涉仪产生的相干光与原子相互作用后借助量子非破坏性测量方法来监测.用精确的波函数方法求解了该原子-光系统的动力学方程,而以往的研究多是采用Holstein-Primakoff(HP)近似.研究中发现,在零检测电流和相同的相干光束的条件下监测凝聚态,可以使测量对原子的影响最小化.在弱原子-光相互作用状态下,通过观察条件概率分布和Q函数分布发现平均自旋方向相对不受影响,而自旋方差沿光耦合的轴方向被压缩.

This paper studies the use of quantum nondemolition(QND)measurement to produce a spin squeezed atomic Bose-Einstein condensate(BEC)in a double-well trap.The spin squeezed atomic BoseEinstein condensate is performed by putting the BECs of a double well in the two arms of a Mach Zehnder interferometer and performing a QND measurement.The dynamics of the light-atom system are solved using an exact wave-function approach,in contrast to previous approaches where approximations were made using techniques like the Holstein-Primakoff approximation.The backaction of the measurement on atoms is minimized by monitoring the condensate at zero detection current and the identical coherent beams.At the weak atom-light interaction limit,we find that the average spin direction is relatively unaffected by observing the conditional probability distribution and the Q function distribution.The spin variance is squeezed along the axis of optical coupling.