BROKEN GAUGE-SYMMETRY IN MACROSCOPIC QUANTUM CIRCUITS

In this paper, we discuss the macroscopic quantum behavior of simple s uper conducting circuits. Starting from a Lagrangian for electromagnet ic field with broken gauge symmetry, we construct a quantum circuit mo del for a superconducting weak link (SQUID) ring, together with the ap propriate canonical commutation relations. We demonstrate that this mo del cm? be used to describe macroscopic excitations of the superconduc ting condensate and the localized charge states found in some ultrasma ll-capacitance weak-link devices.