Quantum phase gate based on multiphoton process in multimode cavity QED

We propose a scheme for implementing a two-qubit quantum phase gate in which the photonic qubits encoded on the cavity modes and a three-level V-type atom passes through the cavity. The location of the resonance is predicted from the use of the theory of multiphoton resonance. Further, we investigate the influence of variations in parameters such as the coupling strengths and detunings on the gate fidelity. We also use the wave-function and the density matrix approaches to analyze theoretically and numerically the effects of decoherence in the implementation of the gate.