Generating and breeding optical Schrodinger's cat states

摘要

Superpositions of macroscopically distinct quantum states, introduced in Schrodinger's famous Gedankenexperiment, are an epitome of quantum "strangeness" and a natural tool for determining the validity limits of quantum physics. The optical incarnation of Schrodinger's cat— the superposition of two opposite-amplitude coherent states — is also the backbone of quantum information processing in the continuous-variable domain. Here we implement two protocols for producing and amplifying optical Schrodinger's cats. In the first protocol we remotely prepare a high-efficiency Schr?dinger cat state by applying the remote state preparation to a NOON state prepared between two parties that are separated by a lossy medium. The second protocol consists in bringing the initial states into interference on a beamsplitter and a subsequent heralding quadrature measurement in one of the output channels. The latter technique enables implementation in an iterative manner, in principle allowing creation of Schrodinger's cat states of arbitrarily high amplitude.