Methods and circuits for reading and writing pi-state-induced circulating currents into superconducting circuits containing magnetic josephson junctions

Abstract

A write circuit for an MJJ-based memory circuit includes first and second current sources configured to generate first and second currents, respectively. The first current imparting an easy axis magnetic field component on an MJJ in a selected memory cell during a write operation. The second current inducing a third current in the selected memory cell that passes through the MJJ, the third current being a seed current for setting a π-state current of the MJJ in a superconducting loop of the selected memory cell. The first current source is configured such that, during the write operation, the MJJ cell transitions: (i) from a π-state, in which a clockwise or counter-clockwise current circulates in the superconducting loop, to a zero-state, in which no current circulates in the superconducting loop, back to the π-state; or (ii) from the zero-state to the π-state; or (iii) from the π-state to the zero-state.