Three-qubit quantum-gate operation with an SQUID in a cavity

We propose a method of realizing a three-qubit quantum gate with a superconducting quantum interference device (SQUID) in a cavity. In this proposal, the gate operation involves the SQUID ground-states and the Fock states of cavity modes b and ĉ. The two field-modes act as the controlling qubits, and the two SQUID states form the target qubit. Since only the metastable lower levels are involved in the gate operation, the gate is not affected by the SQUID decay rates.