Quantum--Classical Interface Based on Single Flux Quantum Digital Logic

Understand

We describe an approach to the integrated control and measurement of a large-scale superconducting multiqubit circuit using a proximal coprocessor based on the Single Flux Quantum (SFQ) digital logic family.

• Coherent control is realized by irradiating the qubits directly with classical bitstreams derived from optimal control theory.
• Qubit measurement is performed by a Josephson photon counter, which provides access to the classical result of projective quantum measurement at the millikelvin stage.
• We analyze the power budget and physical footprint of the SFQ coprocessor and discuss challenges and opportunities associated with this approach.