Realization of quantum gates with multiple control qubits or multiple target qubits in a cavity
We propose a scheme to realize a three-qubit controlled phase gate and a multi-qubit controlled NOT gate of one qubit simultaneously controlling n-target qubits with a four-level quantum system in a cavity. The implementation time for multi-qubit controlled NOT gate is independent of the number of qubit. Three-qubit phase gate is generalized to n-qubit phase gate with multiple control qubits. The number of steps reduces linearly as compared to conventional gate decomposition method. Our scheme can be applied to various types of physical systems such as superconducting qubits coupled to a resonator and trapped atoms in a cavity. Our scheme does not require adjustment of level spacing during the gate implementation. We also show the implementation of DeutschJoza algorithm. Finally, we discuss the imperfections due to cavity decay and the possibility of physical implementation of our scheme.
multi-qubit quantum gates cavity qed solid-state qubit superconducting quantum interference devices (squids) superconducting resonator