Entangled anddisentangled evolution forasingle atomina driven cavity
Perry R. Rice, Julio R. Gea-Banacloche, Luis A. Orozco
Abstract
Foranatominadriven cavity wefind states that arehighly entangled, andthat spontaneous emission cantransiently increase entanglement. Wepropose a correlation function measurement anddiscuss timeevolution ofentanglement. C2003Optical Society ofAmerica OCIScodes:270.5580 Quantum Electrodynamics, 270.5290 Photon Statistics Inarecent, beautiful experiment, Auffeves andcoworkers (1) haveverfied theprediction (2)that, fora two-level atominteracting with asingle modeoftheelectromagnetic field, inacoherent state with a moderately large number ofphotons, thenatural evolution ofthesystem leads toasuperposition state inwhich twodifferent states oftheatomarecorrelated with twodistinguishable states ofthefield, in whatisoften referred toasaSchrodinger cat.Suchsuperpositions ofcorrelated states, ifpure, are naturally entangled states. Interestingly, thepossibility ofpreparing suchentangled superpositions in theabove system (which isdescribed bytheso-called Jaynes-Cummings model, orJCM)arises from theexistence, inthis model, ofspecial trajectories along whichthejoint evolution offield andatomis toagoodapproximation unentangled, i.e., factorizable. Itisthecoherent superposition ofsuch trajectories that results inanentangled state.