Current microwave photon detectors based on superconducting qubits operate in cycles, so photons arriving during the measurement and reset steps are missed.

In our new pre-print, led by Vyom Kulkarni and co-authored by Aamir Ali, Simon Sundelin, and Prof. Simone Gasparinetti, we demonstrate a photodetector based on a superconducting artificial molecule that can continuously resolve individual microwave photons.

The device achieves a continuous detection efficiency of 47% with a dark-count rate of 1.3 kHz. This research aligns with our ongoing work at 202Q-lab and WACQT to use superconducting circuits to advance quantum technologies.

We envisage that this single-photon microwave photodetector, with its unique combination of high efficiency and always-on functionality, could be useful for fundamental science experiments ranging from electron-spin fluorescence to search for elusive particles of dark matter in the universe.

Read the full pre-print: https://arxiv.org/abs/2608.12972