Abstract

The basic elements necessary for a practical quantum computer may be realizable by superconducting integrated electronics. Superconducting Josephson junction circuits that may serve as the qubits in a possible quantum computer have been proposed and evidence for quantum coherent behavior in two different superconducting qubit circuits has been reported. In such circuits the qubit states correspond to the two possible "flux states" of a superconducting loop containing one or more Josephson junctions. Estimates of decoherence times are promising, milliseconds or longer, and experimental measurement of decoherence times are ongoing. On-chip qubit control circuits that employ Rapid Single Flux Quantum (RSFQ) Josephson electronics are being developed and promise to allow control of qubits at the picosecond level of timing accuracy. Likewise, RSFQ circuit structures to mediate the interaction of Josephson qubits have been conceptualized. Two further advantages of superconductors are that superconductors are ideal magnetic shields and the nonlinear nature of Josephson junctions enables excellent qubit isolation and electronically controllable interactions with flux based qubits. Perhaps most important is that if the basic elements of a quantum computer can be demonstrated in superconducting integrated circuit technology then familiar microelectronic fabrication methods will enable us to scale the technology up to large complex circuits.

© 2001 Optical Society of America