A qubit device based on manipulations of Andreev bound states in double-barrier Josephson junctions

A qubit system exploiting manipulations of the Andreev bound state (ABS) levels in the SINIS junction by applying appropriate bias voltages and transport currents is suggested. The parameters of the SINIS setup may be chosen in such a way that only two ABS levels are present; this is in agreement with our experimental data obtained using Nb/Al double-barrier junctions. In the qubit Hamiltonian, H, the two ABS levels are presented as the ‘↑’ and ‘↓’ spin states, while the controlling physical parameters (voltage across one of the barriers and the transport current) are mapped to the ‘magnetic fields’ Bxn and Bzn. The phase decoherence time is estimated.