原子系综中光学腔增强的Duan-Lukin-Cirac-Zoller写过程激发实验

原子系综中的Duan-Lukin-Cirac-Zoller(DLCZ)过程是产生光与原子(量子界面)量子关联和纠缠的重要手段.当一束写光与原子发生作用时,将会产生斯托克斯(Stokes)光子的自发拉曼散射,并同时产生一个自旋波(spin-wave)存储在原子系综中,上述过程即为DLCZ量子记忆产生过程.这一过程被广泛地研究.本文将87Rb原子系综放入驻波腔,并使Stokes光子与光学腔共振,我们观察到有腔且锁定的情况下Stokes光子产生概率比无腔时增大了8.7倍.在此条件下研究了Stokes光子产生概率和写光功率的关系,Stokes光子产生概率随写光功率线性增大.

Optical cavity enhancement experiment of Duan-Lukin-Cirac-Zoller writing excitation process in atomic ensemble

The Duan-Lukin-Cirac-Zoller(DLCZ)process in the atomic ensemble is an important means to generate quantum correlation and entanglement between photons and atoms(quantum interface).When a write pulse acts on atoms,the DLCZ quantum memory process will be generated,which has been extensively studied.In the process a spontaneous Raman scattering(SRS)of a Stokes photon is generated,and a spin-wave excitation stored in the atomic ensemble is created at the same time.The higher probability of the generation of Stokes photons will cause more noise and reduce entanglement.On the contrary,the low generation probability of Stokes photons affects the success probability of entanglement distribution on a quantum repeater.How to increase generation probability of Stokes photons without causing more noise is an urgent problem to be resolved.In this work,a 87Rb atomic ensemble is placed in a standing wave cavity which resonates with the Stokes photon.This cavity has a trip length of 0.6 m and a free spectral range(FSR)of 256 MHz.The optical loss of all the optical elements in this cavity is 9%,of which 4%loss originates from the other optical elements and 5%loss from the vacuum chamber of the magneto-optical trap(MOT).The fineness of the cavity with the cold atoms is measured to be~19.1.By calculating the total probability of Stokes photon emission out of the cavity,we derive the enhancement factor of this standing wave cavity when the cavity loss is l.When this cavity is locked with PDH frequency locking technique,we observe that the production probability of the Stokes photons is 8.7 times higher than that without cavity due to the optical cavity enhancement effect.Under this condition,the relationship between the generation probability of Stokes photons and the power of write beam is studied.The write excitation probability changes linearly with the power of write beam.This work provides an experimental solution to reducing the noise caused by time multimode operation in DLCZ scheme.