Control of multilevel voltage states in a hysteretic superconducting-quantum-interference-device ring-resonator system

In this paper we study numerical solutions to the quasiclassical equations of motion for a superconducting-quantum-interference device ring-radio frequency (rf) resonator system in the regime where the ring is highly hysteretic. In line with experiment, we show that for a suitable choice of ring circuit parameters the solutions to these equations of motion comprise sets of levels in the rf voltage-current dynamics of the coupled system. We further demonstrate that transitions, both up and down, between these levels can be controlled by voltage pulses applied to the system, thus opening up the possibility of high order (e.g., 10 state), multilevel logic and memory.