Millikelvin digital-to-analog converter for superconducting quantum processors

TL;DR

This paper introduces a superconducting millikelvin DAC that enables in-situ qubit tuning with minimal coherence impact, reducing wiring complexity in superconducting quantum processors.

Contribution

It demonstrates a superconducting digital-to-analog converter integrated with fluxonium qubits, programmable via single-flux-quantum pulses, compatible with existing SFQ routing.

Findings

DAC enables in-situ flux tuning without degrading coherence

Reduces wiring and calibration overhead in quantum processors

Operates effectively at millikelvin temperatures

Abstract

Scaling superconducting quantum processors is increasingly constrained by the wiring, heat load, and calibration overhead associated with delivering high-resolution analog signals from room temperature to qubits at millikelvin temperature. Here we demonstrate a superconducting digital-to-analog converter (DAC) integrated with high-coherence fluxonium qubits in a multi-chip module architecture. The DACs generate persistent analog flux signals for tuning qubit parameters and are programmed deterministically using single-flux-quantum (SFQ) pulses, providing a digital interface compatible with established SFQ routing and demultiplexing technologies. Operating at millikelvin temperature, the DACs enable in-situ tuning of fluxonium qubits without measurable degradation of qubit coherence. The presented device provides a static control primitive for flux-tunable qubits, enabling parameter homogenization and eliminating the need for individual room-temperature DC bias lines. These results establish SFQ-programmable millikelvin DACs as a building block for digitally controlled superconducting quantum processors.