Scheme for Implementing an N-Qubit Phase Gate via Selective Atom--Field Interaction with Cavity Quantum Electrodynamics

A scheme for implementing a two-qubit phase gate with atoms sent through a high-Q optical cavity is proposed by choosing nonidentical coupling constants between the atoms and cavity. The atomic spontaneous emission can be suppressed due to the large atom--field detuning. Moreover, the scheme can be generalized to implement an N-qubit phase gate and the gating time
does not change with an increase of the number of qubits.