Information-theoretical approach to Josephson tunneling

A simplified Hamiltonian model of pair tunneling between two weakly coupled superconductors is used to obtain the ac Josephson current. A closed operator algebra is defined through commutation with the Hamiltonian. With the use of information theory, we find a subalgebra (quasi-angular-momentum operators) that allows us to obtain naturally the dependence of the Josephson current on the phase, as well as a geometric interpretation of the phase. The quasi-spin algebra permits us to find a consistent solution for the imbalance of charge without resorting to further constraints.