n -qubit-controlled phase gate with superconducting quantum-interference devices coupled to a resonator

We present a way to realize an n -qubit controlled phase gate with superconducting quantum-interference devices (SQUIDs) by coupling them to a superconducting resonator. In this proposal, the two logical states of a qubit are represented by the two lowest levels of a SQUID. An intermediate level of each SQUID is utilized to facilitate coherent control and manipulation of quantum states of the qubits. It is interesting to note that an n -qubit controlled phase gate can be achieved with n SQUIDs by successively applying a π/2 Jaynes-Cummings pulse to each of the n-1 control SQUIDs before and after a π Jaynes-Cummings pulse on the target SQUID.