Fast recovery of niobium-based superconducting resonators after laser illumination

Interfacing superconducting microwave resonators with optical systems enables sensitive photon detectors, quantum transducers, and related quantum technologies. Achieving high optical pulse repetition is crucial for maximizing the device throughput. However, light-induced deterioration, such as quasiparticle poisoning, pair-breaking-phonon generation, and elevated temperature, hinders the rapid recovery of superconducting circuits, limiting their ability to sustain high optical pulse repetition rates. Understanding these loss mechanisms and enabling fast circuit recovery are therefore critical. In this work, we investigate the impact of optical illumination on niobium nitride and niobium microwave resonators by immersing them in superfluid helium-4 and demonstrate a three-order-of-magnitude faster resonance recovery compared to vacuum. By analyzing transient resonance responses, we provide insights into light-induced dynamics in these superconductors, highlighting the advantages of niobium-based superconductors and superfluid helium for rapid circuit recovery in superconducting quantum systems integrated with optical fields. High-speed optical pulses can enhance system performance and data throughput in photonic-microwave hybrid circuits, but repeated illumination can degrade superconducting resonators’ performance. Here, by conducting experiments in vacuum and superfluid helium, the authors reveal the mechanisms of light-induced loss and demonstrate a three order-of-magnitude faster resonance recovery of niobium-based superconducting resonators in the superfluid helium environment.