The effect of magnetic field on the intrinsic detection efficiency of superconducting single-photon detectors

TL;DR

This study experimentally examines how magnetic fields influence photon detection efficiency in superconducting single-photon detectors, revealing that magnetic fields do not enhance intrinsic detection efficiency but affect dark count rates.

Contribution

It provides new insights into the effects of magnetic fields on superconducting detectors, showing no intrinsic efficiency enhancement in magnetic fields and distinguishing dark and light count behaviors.

Findings

Magnetic field modifies quasiparticle density of states at low fields.

Detection efficiency is unaffected by magnetic fields beyond vortex entry.

Dark count rates are influenced by magnetic fields even when detection efficiency is not.

Abstract

We experimentally investigate the effect of a magnetic field on photon detection in superconducting single-photon detectors. At low fields, the effect of a magnetic field is through the direct modification of the quasiparticle density of states of the superconductor, and magnetic field and bias current are interchangable, as is expected for homogeneous dirty-limit superconductors. At the field where a first vortex enters the detector, the effect of the magnetic field is reduced, up until the point where the critical current of the detector starts to be determined by flux flow. From this field on, increasing the magnetic field does not alter the detection of photons anymore, whereas it does still change the rate of dark counts. This result points at an intrinsic difference in dark and light counts, and also shows that no enhancement of the intrinsic detection efficiency of a straight SSPD wire is achievable in a magnetic field.