A solid-state quantum computing qubit includes a multi-terminal junction coupled
to a superconducting loop where the superconducting loop introduces a phase shift
to the superconducting order parameter. The ground state of the supercurrent in
the superconducting loop and multi-terminal junction is doubly degenerate, with
two supercurrent ground states having distinct magnetic moments. These quantum
states of the supercurrents in the superconducting loop create qubits for quantum
computing. The quantum states can be initialized by applying transport currents
to the external leads. Arbitrary single qubit operations may be performed by varying
the transport current and/or an externally applied magnetic field. Read-out may
be performed using direct measurement of the magnetic moment of the qubit state,
or alternatively, radio-frequency single electron transistor electrometers can
be used as read-out devices when determining a result of the quantum computing.
Further, qubits as described above can form arrays of qubits for performing controlled
quantum computing calculations. In one example, an array of qubits can be utilized
as a random number generator.
