  We present the design of a superconducting qubit that has circulating
currents of opposite sign as its two states. The circuit consists of three
nano-scale aluminum Josephson junctions connected in a superconducting loop and
controlled by magnetic fields. The advantages of this qubit are that it can be
made insensitive to background charges in the substrate, the flux in the two
states can be detected with a SQUID, and the states can be manipulated with
magnetic fields. Coupled systems of qubits are also discussed as well as
sources of decoherence.
