Controlled-NOT logic gate based on conditional spectroscopy

A controlled-NOT logic gate based on conditional rotation of a target qubit by applying a microwave pulse of appropriate frequency has been demonstrated experimentally for a pair of superconducting~flux qubits [Plantenberg et. al., Nature 447, 836 (2007)] . Here we discuss a related construction appropriate for coupled phase qubits~or a phase~qubit coupled to a resonator.~Our results show that an intrinsic fidelity of more than 99{\%} is~achievable~in about 45ns.