Pulse-generator-based bias-level sensors for reciprocal quantum logic

Abstract

Pulse-generator-based reciprocal quantum logic (RQL) bias-level sensors are fabricated on an RQL integrated circuit (IC) to sample AC or DC bias values provided to operational RQL circuitry on the RQL IC. The bias-level sensors include pulse generators having strengthened or weakened bias taps (transformer couplings to RQL AC clock resonators or DC bias lines) as compared to bias taps of Josephson transmission lines in the operational RQL circuitry, or Josephson junctions (JJs) with larger or smaller critical currents as compared to JJs in the operational RQL circuitry. Pulse generators with weakened bias taps or larger JJs can have lower limits of their operational ranges placed near an optimal bias point at the centroid of the operating region of the operational RQL circuitry. The bias-level sensors can be staged by relative strength to indicate whether a provided bias value is an improvement when varied over a range.