Transmon qubits under laser illumination

Microwave-to-optical quantum state transfer enables the interconnection of remote superconducting quantum processors via optical fiber links. Achieving high conversion efficiency necessitates an intense optical pump, yet direct optical exposure of superconducting circuits often degrades their performance. In this work, we investigate the behavior of transmon qubits under laser illumination in both vacuum and superfluid helium-4. We observe that qubits recover significantly faster in superfluid helium than in vacuum, with a power handling improvement of over 10 dB. This enhanced cooling capacity supports higher optical pump powers, enabling faster qubit control and readout. These findings open a promising pathway for the efficient implementation of quantum transduction devices.