GEOMETRY OF THE JOSEPHSON EFFECT

We investigate the geometry of the Josephson tunneling current between two superconductors separated by an insulator. We obtain the geometri c phase and the Fubini-Study metric in Feynman's treatment of the Jose phson effect. The zero-voltage Josephson tunneling current is shown to be purely a geometric quantity, proportional to the speed of transpor tation of the state vector in its projective Hilbert space, The time r ate of change of the non-cyclic geometric phase is calculated and is r elated to this speed. (C) 1997 Elsevier Science B.V.