Single Flux Quantum based electronics for control and readout of superconducting qubits.

Superconducting quantum information systems require a mix of continuous-wave AC, pulse-modulated AC, and DC signals for control and readout. There are significant advantages in terms of scaling, physical footprint, latency, signal integrity, and power consumption by moving these sources to 4 K or below, inside the cryostat. In this talk we present an experimental demonstration generating spectroscopy tones at 4 K to measure a transmon qubit’s energy level spacings at 100 mK. The spectroscopy tones are generated by a series of Josephson junctions at 4 K driven by a sigma-delta pulse stream from room temperature. This experiment was our first step in optimizing the Josephson arbitrary waveform synthesizer (JAWS) circuit for controlling quantum systems in a scalable manner. We also discuss further steps needed to generate pulsed signals for qubit preparation, cryogenic readout, and digital superconducting circuits at 4K for signal processing and feedback.