We present an approach to realize universal two-bit quantum gates using two SQUID flux qubits. In this approach the basic unit consists of two inductively coupled SQUIDs with realistic device parameters. Quantum logical gates are implemented by applying resonant microwave pulse to the qubits. This procedure is demonstrated by realizing a controlled-NOT (CNOT) gate and the maximally entangled states of the coupled qubits through highly accurate numerical solution of the time-dependent Schrodinger equation of the system. This coupling scheme is simple and can be readily extended to many-qubit circuits required for scalable quantum information processing.
Zhou, ZY; Chu, SI; Han, SY. Quantum entanglement and controlled logical gates using coupled SQUID flux qubits. IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY. June 2005. 15(2, Part 1): 833-836.