Scalable quantum computation via a coherent state input–output process in a low-Q cavity in the atom–cavity intermediate coupling region

Abstract

We propose a basic scheme to construct a hybrid controlled phase-flip (CPF) gate between a flying pulse qubit and a stationary atomic qubit, assisted by a cavity input–output process for a low-Q cavity in the atom–cavity intermediate coupling region. The qubits can be encoded on the coherent states and ground states of the single-trapped L-level atom, respectively. We present a theoretical model of the hybrid CPF gate, whose basic strategy is to control the reflectivity of the input coherent optical pulse to obtain a phase shift conditioned by the different internal atomic states by adjusting the parameters of the cavity quantum electrodynamics (CQED) system. The resulting basic scheme can be used to construct nonlocal gates between remote atomic qubits confined in spatially separated cavities, and also for the generation of an atomic cluster state. The performance and experimental feasibilities of the proposed scheme indicate that it is robust against practical noise and feasible with current technologies. Thus, our scheme is applicable for use in large-scale quantum computation.