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

TL;DR

This paper presents a superconducting multiqubit control and measurement system using Single Flux Quantum digital logic, enabling integrated quantum-classical interfacing with potential for scalable quantum computing.

Contribution

It introduces a novel SFQ-based coprocessor for integrated control and measurement of superconducting qubits, combining classical control with quantum measurement techniques.

Findings

Efficient qubit control via classical bitstreams from optimal control theory

Use of Josephson photon counter for projective quantum measurement

Analysis of power and physical footprint of SFQ coprocessor

Abstract

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.