Type-1.5 SNSPD: Interacting vortex theory of two bandgap superconducting single photon detectors

TL;DR

This paper introduces a new type-1.5 superconducting nanowire single photon detector (SNSPD) based on two-gap superconductors like MgB2, revealing unique vortex interactions that improve performance over traditional type-2 SNSPDs.

Contribution

It develops a theoretical framework for type-1.5 SNSPDs, highlighting vortex-vortex interactions and their impact on photon detection and dark count suppression.

Findings

Single photons can seed multiple vortices in the hotspot.

Dark counts are suppressed in the type-1.5 regime.

Vortex physics in two-gap superconductors can enhance quantum device performance.

Abstract

Photon detectors based on type-2 superconductors have found widespread applications from on-chip quantum computing to quantum remote sensing. Here, we develop the theory for a new class of type-1.5 superconducting nanowire single photon detectors (SNSPDs) based on two bandgap superconductors with high transition temperatures such as MgB2 (Tc ~38.6K). We show that vortex-vortex interactions in two component condensates lead to a unique operating regime where single photons can seed multiple vortices within a hotspot. We also show that dark counts are suppressed in the type-1.5 regime compared to the widely studied type-2 SNSPDs. Our work opens the door for exploring the unique vortex physics of two-gap superconductors for quantum device applications.