Superconducting persistent-current qubit

We present the design of a superconducting qubit that has circulating curre nts of opposite sign as its two states. The circuit consists of three nanos cale aluminum Josephson junctions connected in a superconducting loop and c ontrolled by magnetic fields. The advantages of this qubit are that it can be mode insensitive to background charges in the substrate, the flux in the two states: can be detected with a superconducting quantum interference de vice, and the states can he manipulated with magnetic fields. Coupled syste ms of qubits are also discussed as well as sources of decoherence. [S0163-1 829(99)00746-8].