Inductive coupling of two superconducting loops with three Josephson junctions

A superconducting loop with three Josephson junctions can behave as a macroscopic quantum two-level system, which could be used as a flux qubit. Coupling of qubits is necessary to realize a quantum computer. We studied the classical states of two such loops which are inductively coupled. When the magnetic flux in each loop is near half a flux quantum, there are two classical states in which the magnetic moments of the loops are parallel and anti-parallel respectively, while the anti-parallel state is energetically favorable. The magnetic flux due to the coupled loops is calculated as a function of the frustration. (C) 2003 Elsevier Science B.V. All rights reserved.