Conditions foraQND measurementofspinincold87Rb
S. R. deEchaniz, Marcin Kubasik, Herbert Crepaz, Morgan W. Mitchell, Eugene Simon Polzik · 2005
Therehasrecently beenmuchinterest incoupling light withatomicensembles todevelop a quantum interface. Several proposals havebeenpublished to utilise this kindofinterface forspinsqueezing, quantummemories, quantumteleportation, andentanglement[1].Manyofthese proposals havebeenrealised experimentally. Spinsqueezing isthesimplest ofthese applications, andhasbeendemonstrated several times. However, all ofthese realisations havebeen performed using squeezed states oflight orsamples in vapour cells withrelatively lowsignal tonoise ratio. Wepropose ascheme togenerate spin squeezing via aquantumnon-demolition (QND)measurement [2] in acoldsample of87Rbatomsusing the5S1/2(F = 1) hyperfine ground state. Inthissystem weexpect to haveamuchhigher signal tonoise ratio thaninprevious work.Suitable Zeemansubstates andoperators toperform theQND interaction inthis schemeare identified, together withthepossible sources oferror andnoise arising fromthese choices. Spinsqueezing iscreated bysending anoff-resonant pulse oflight inacoherent polarisation statethrough anatomic sample prepared inacoherent spinstate. Thelight andatomsexchange quantumfluctuations duetothedipole interaction; squeezing isthen achieved byaQND measurement ofonecomponent oftheatomic spin.Thecoupling between light and atomsinthis kindofschemes isdescribed bythefluctuation relatioils [2]