An RSFQ variable duty cycle oscillator for driving a superconductive qubit

We design an RSFQ oscillator with a variable duty cycle to drive a superconductive qubit. This design has been optimized to minimize the decoherence when coupled to the superconductive persistent current qubit. A continuous RSFQ ring oscillator reads the contents of a Non-Destructive Read Out memory cell. By using two out-of-phase counters to Set and Reset the cell, we can vary the duty cycle of the pulses read from the memory cell. This train of flux quanta is filtered, then used to drive the persistent current qubit. The precision is sufficient to measure relaxation time and possibly Rabi oscillations.