CHARGE REPRESENTATION OF A SMALL 2-DIMENSIONAL JOSEPHSON-JUNCTION ARRAY IN THE QUANTUM REGIME

Using the charge representation, we calculate the ground state energy and the critical current of a small two-dimensional Josephson junction array subject to both charge and magnetic frustration. In the quantum regime the ground state of the array is a superposition of charge sta tes, allowing a supercurrent to flow through the circuit. Both the gro und state energy and the critical current can be tuned by the two frus trations. We show that the notion of a vortex is compatible with a cha rge representation of the array.