Multi-Terminal Superconducting Phase Qubit

Abstract

Mesoscopic multi-terminal Josephson junctions are novel devices that provide weak coupling between several bulk superconductors through a common normal layer. Because of the nonlocal coupling of the superconducting banks, a current flow between two of the terminals can induce a phase difference and/or current flow in the other terminals. This "phase dragging" effect is used in designing a new type of superconducting phase qubit, the basic element of a quantum computer. Time-reversal symmetry breaking can be achieved by inserting a pi-phase shifter into the flux loop. Logical operations are done by applying currents. This removes the necessity for local external magnetic fields to achieve bistability or controllable operations.