Implementation of Nonlocal Controlled-NOT Gate via a Cavity Input-Output Process

Abstract

Quantum entanglement, which is a novel feature distinguishing quantum mechanics from classical physics, has been widely used in quantum information processing [1{7] and quantum computing [8,9]. In recent years, people have paid much attention to the quantum logic gate and have devoted themselves to the implementation of the quantum logic gate with di erent physical systems, such as cavity quantum electrodynamics (QED) [10], linear optics [11], ion trap [12], nuclear magnetic resonance (NMR) [13], etc. It is well known that quantum information can be encoded in the states of atom, ion and photon. However, compared with the atom and the ion, the photon has some special advantages; for example, it weakly interacts with the environment and the operational convenience of single-qubit and two-qubit logic gates in linear optical ways can be realized. All these features make the photon more appropriate as an ideal carrier for quantum information and more appropriate for use as ying qubits that interact with stationary qubits (atom or ion). Recently, Duan and Kimble proposed a scheme to implement a two-photon quantum controlled phase ip (CPF) gate via a cavity input-output process [14]. In