Microwave Circulation in an Extended Josephson Junction Ring

Circulators are nonreciprocal devices that enable directional signal routing. Nonreciprocity, which requires time-reversal symmetry breaking, can be produced in waveguides in which the propagation medium moves relative to the waveguide at a moderate fraction of the wave speed. Motivated by this effect, here we propose a design for nonreciprocal microwave transmission based on an extended, annular Josephson junction, in which the propagation medium consists of a train of moving fluxons. We show how to harness this to build a high-quality resonant microwave circulator, and we theoretically evaluate the anticipated performance of such a device.