QUANTUM CIRCUIT-THEORY AND MEASUREMENTS ON Y-BA-CU-O GRAIN-BOUNDARY WEAK-LINK BRIDGES

The quantum system associated with a resistor-shunted weak-link juncti on circuit may be described in terms of a single Lagrangian. In this r epresentation the degrees of freedom internal to the dissipative energ y of the resistor can be systematically separated from the Hamiltonian formulation of the circuit. This allows us to solve the quantum state s of the junction while the effects of the resistor on the circuit are included as a Lagrangian multiplier. In this manner the effects of th e measuring apparatus or resistor on the quantum state of the junction may be calculable. The calculations are in very good agreement with e xperiments.