A Low-Noise and High-Stability DC Source for Superconducting Quantum Circuits

TL;DR

This paper introduces QPower, a custom dual-channel DC source with ultra-low noise and high stability, enabling improved qubit coherence and scalability in superconducting quantum processors.

Contribution

The paper presents a novel, low-noise, high-stability DC source module specifically designed for large-scale superconducting quantum processors, addressing limitations of commercial instruments.

Findings

Achieved noise spectral density of 20 nV/√Hz at 10 kHz

Maintained output ripple below 500 μV within 20 MHz bandwidth

Enabled qubit coherence times of T₁=87.6 μs and T₂=5.1 μs in a 66-qubit processor

Abstract

With the rapid scaling of superconducting quantum processors, electronic control systems relying on commercial off-the-shelf instruments face critical bottlenecks in signal density, power consumption, and crosstalk mitigation. Here we present a custom dual-channel direct current (DC) source module (QPower) dedicated for large-scale superconducting quantum processors. The module delivers a voltage range of $\pm$7 V with 200 mA maximum current per channel, while achieving the following key performance benchmarks: noise spectral density of 20 nV/$\sqrt{\mathrm{Hz}}$ at 10 kHz, output ripple $<$500 $\mu$V$_{\mathrm{pp}}$ within 20 MHz bandwidth, and long-term voltage drift $<$5 $\mu$V$_{\mathrm{pp}}$ over 12 hours. Integrated into the control electronics of a 66-qubit quantum processor, QPower enables qubit coherence times of $T_1 = 87.6~\mu\mathrm{s}$ and Ramsey $T_2 = 5.1~\mu\mathrm{s}$, with qubit resonance frequency drift constrained to $\pm$40 kHz during 12-hour operation. This modular design is compact in size and efficient in energy consumption, providing a scalable DC source solution for intermediate-scale quantum processors with stringent noise and stability requirements, with potential extensions to other quantum hardware platforms and precision measurement.