Expanding possibilities for quantum state engineering

Abstract

Abstract Generation of the states with fidelity as close as possible to high-amplitude Schrödinger cat states (SCSs) is studied. The input state in the main mode is exclusively mixed with the Fock states on successive beam splitters after which a number of auxiliary modes emerge. Subsequently, all the modes are properly displaced. The resulting state is projected onto the vacuum states of every auxiliary mode for conditional generation of the target states in the main mode. We demonstrate a possibility to generate Schrödinger cat qudits (SCQs) which may approximate SCSs of large size β ranging from β = 2 to β = 3 with high fidelity close to 0.99 . The method is based on the use of the concept of SCQs being the best approximation of the SCSs in the finite Hilbert space with basic displaced number states characterized by the displacement amplitude α . Different states (e.g. number state or coherent state or superposed state) are selected as the input to the optical scheme. In particular, we show that an input Schrödinger kitten state (i.e. small-size SCS) can give rise to an output SCS of larger size. We also test the proposed approach in a realistic scenario.