# Josephson radiation and shot noise of a semiconductor nanowire junction

## TL;DR

This study investigates Josephson radiation and shot noise in an InSb nanowire junction, revealing detailed microwave environment effects and evidence of single-electron states through photon-assisted tunneling.

## Contribution

It provides the first detailed measurement of Josephson radiation and shot noise in a semiconductor nanowire junction, including microwave environment characterization.

## Key findings

- Zero frequency impedance Z(0)=492 Ω
- Cutoff frequency f_0=33.1 GHz
- Fano factor F≈1 indicating single-electron states

## Abstract

We measured the Josephson radiation emitted by an InSb semiconductor nanowire junction utilizing photon assisted quasiparticle tunneling in an AC-coupled superconducting tunnel junction. We quantify the action of the local microwave environment by evaluating the frequency dependence of the inelastic Cooper-pair tunneling of the nanowire junction and find the zero frequency impedance $Z(0)=492\,\Omega$ with a cutoff frequency of $f_0=33.1\,$GHz. We extract a circuit coupling efficiency of $\eta\approx 0.1$ and a detector quantum efficiency approaching unity in the high frequency limit. In addition to the Josephson radiation, we identify a shot-noise contribution with a Fano factor $F\approx1$, consistently with the presence of single electron states in the nanowire channel.