Superconducting nanowire single-photon detectors (SNSPDs) offer high-quantum-efficiency and low-dark-count-rate single-photon detection. In a growing number of cases, large magnetic fields are being incorporated into quantum microscopes, nanophotonic devices, and sensors for nuclear and high-energy physics that rely on SNSPDs, but superconducting devices generally perform poorly in large magnetic fields. Here, we demonstrate robust performance of amorphous SNSPDs in magnetic fields of up to $\pm 6$ T with a negligible dark-count rate and unchanged quantum efficiency at typical bias currents. Critically, we also show that the SNSPD can be used as a magnetometer with a sensitivity of better than $100\mu \mathrm{T}/\sqrt{\mathrm{Hz}}$ and as a thermometer with a sensitivity of $20\mu \mathrm{K}/\sqrt{\mathrm{Hz}}$ at 1 K. Thus, a single-photon detector integrated into a quantum device can be used as a multifunctional quantum sensor capable of describing the temperature and magnetic field on chip simply by varying the bias current to change the operating modality from single-photon detection to thermometry or magnetometry.

• Received 18 March 2021
• Revised 19 September 2021
• Accepted 9 November 2021

DOI:https://doi.org/10.1103/PhysRevApplied.16.064059