Generating a Schrodinger-cat-like state via a coherent superposition of photonic operations

We propose an optical scheme to generate a superposition of coherent states with enhanced size adopting an interferometric setting at the single-photon level currently available in the laboratory. Our scheme employs a nondegenerate optical parametric amplifier together with two beam splitters so that the detection of single photons at the output conditionally implements the desired superposition of second-order photonic operations. We analyze our proposed scheme by considering realistic on-off photodetectors with nonideal efficiency in heralding the success of conditional events. A high-quality performance of our scheme is demonstrated in view of various criteria such as quantum fidelity, mean output energy, and measure of quantum interference.We thank M. S. Kim for the refined idea of feasible experimental setup, M. Paternostro for helpful suggestions, H.-J. Kim for discussion about Gaussian integration, and U. L. Andersen and C. R. Muller for providing useful information on photodetectors. H. Nha was supported by NPRP Grant No. 4-554-1-084 from Qatar National Research Fund. C.-W.L., J.L., and H.J. were supported by the World Class University (WCU) program and the KOSEF grant funded by the Korea government (MEST) (Grant No. R11-2008-095-01000-0)