An Integrated Broadband Low-Noise Microwave Source for Superconducting Quantum Circuits

Abstract

Scaling superconducting quantum processors increasingly relies on custom control electronics that can simultaneously satisfy spectral purity, multi-channel isolation, and long-term stability within a compact and integrated platform. Here we present Quantum microwave source (QMW), a classical three-channel broadband low-noise microwave source that consolidates qubit XY drive, readout excitation, and Josephson parametric amplifier (JPA) pump generation onto a single hardware module operating from 4 to 14 GHz with an output power range of -20 to +10 dBm. Electronic characterization yields a spurious-free dynamic range greater than 55 dB, equivalently a largest spur below -55 dBc, a phase noise as low as -110 dBc/Hz at 10 kHz offset for a 5 GHz carrier and below -103 dBc/Hz at the same offset across the full band, and output power stability within 0.1 dB over 24 hours. Integrated into the control chain of a 36-qubit superconducting processor, QMW pumps a JPA to 19.2 dB gain to enable high-SNR single-shot readout, while sustaining qubit coherence times of T 1 = 60.1 ± 0.8 μs, T 2,Ramsey = 24.2 ± 1.5 μs, and T 2,echo = 58.6 ± 2.1 μs, and an average single-qubit gate fidelity of 99.95 ± 0.05% measured by randomized benchmarking. The compact and modular nature of QMW provides a scalable microwave generation solution for largescale superconducting quantum processors, with potential extensions to other quantum hardware platforms and precision measurement applications.