Amplification of optical Schr\"{o}dinger cat states with implementation protocol based on frequency comb

Abstract

We proposed and analyzed a scheme to generate large-size Schr\"{o}dinger cat states based on linear operations of Fock states and squeezed vacuum states and conditional measurements. By conducting conditional measurements via photon number detectors, two unbalanced Schr\"{o}dinger kitten states combined by a beam splitter can be amplified to a large-size cat state with the same parity. According to simulation results, two Schr\"{o}dinger odd kitten states of $\beta=1.06$ and $\beta=1.11$ generated from one-photon-subtracted squeezed vacuum states of $-$3 dB, are amplified to an odd cat state of $\beta=1.73$ with a fidelity of $F=99\%$. A large-size Schr\"{o}dinger odd cat state with $\beta=2.51$ and $F=97.30\%$ is predicted when the input squeezed vacuum states are increased to $-$5.91 dB. According to the analysis on the impacts of experimental imperfections in practice, Schr\"{o}dinger odd cat states of $\beta>2$ are available. A feasible configuration based on a quantum frequency comb is developed to realize the large-size cat state generation scheme we proposed.