用于光学薛定谔猫态制备的滤波设计与滤波腔腔长测量  

Filter cavity design and length measurement for preparing Schrödinger cat state

作　　者：翟泽辉[1] 郝温静 刘建丽 段西亚 Zhai Ze-Hui;Hao Wen-Jing;Liu Jian-Li;Duan Xi-Ya(School of Physics and Electronic Engineering,Shanxi University,Taiyuan 030006,China)

机构地区：[1]山西大学物理电子工程学院,太原030006

出　　处：《物理学报》2020年第18期70-75,共6页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2016YFA0301404);国家自然科学基金(批准号:11504217)资助的课题.

摘　　要：光学薛定谔猫态不仅是量子力学基本问题的主要研究对象之一,也是连续变量量子信息的重要资源.在其实验制备中,对触发光路进行滤波操作是决定猫态的纯度、产率等重要参数的关键环节.本文介绍实验中的滤波设计以及滤波腔腔长的测量方法.依据设计要求,腔长lFC应满足条件189μm>lFC>119μm,如此短的腔长用常规方法难以较准确地测量.利用高阶横模的古依相移测得腔长为141μm,满足设计要求.该测量方法不依赖于腔内任何介质的色散等特性,具有一定的普遍性.Optical Schrodinger cat state is not only one of the basic elements of quantum mechanics,but also a pivotal resource of continuous-variable quantum information.The non-Gaussian operation in its preparation can also be a key technology in distilling continuous-variable squeezing and entanglement.In the experimental preparation,a small part of a beam of vacuum squeezing is separated and detected as the trigger of appearance of Schrodinger cat state.Filter operation in the trigger optical path is important since it affects dark counts of single photon detector,frequency mode matching of trigger mode and signal mode,and preparing rate of the Schrodinger cat state,etc.In this paper,we describe the design of optical filter in the trigger path and the measurement of the filter cavity length.According to the design,filter cavity length lFC should satisfy 189μm>lFC>119μm.This cavity length is too small to be measured with a ruler.To measure the cavity length,we introduce an optical method,in which Gouy phases of Hermite Gaussian transverse modes TEM00 and TEM10 are used.When the cavity length is scanned,resonant peaks and the corresponding scanning voltages are recorded.From theoretical derivation,the cavity length is related to the filter cavity piezo response to the scanning voltage Ψ′G,the slope rate of piezo scanning voltage U′,and the time distance between TEM00 and TEM10 resonant peaks Δt.The finally measured cavity length is lFC=(141±28)μm,which satisfies the design requirement.The measurement error mainly originates from inaccurate fitting of Ψ′G and U′,and readout error of Δt.It is shown that the error of Ψ′G is dominant since less data are used in the curve fitting.The measurement error is expected to be reduced if much more data of piezo response to scanning voltage are collected and used to fit Ψ′G with higher order polynomials.The proposed measurement method of short cavity length needs neither wide tuning laser nor any peculiar instrument,and does not depend on any dispersion property o

关 键 词：薛定谔猫态 压缩态 滤波腔 古依相移 

分 类 号：O431.2[机械工程—光学工程] TN713[理学—光学]