Detecting Single Photons with Graphene-Based Josephson Junctions

Abstract

In this work I present theory, modeling, and experimentation demonstrating that the graphene-based Josephson junction (GJJ) is a capable system for the detection of single photons across the electromagnetic spectrum, from the microwave to the infrared. Two different detection mechanisms are exposed: 1) heating of the graphene weak link in the GJJ and 2) quasiparticle generation in the GJJ superconducting contacts. The first relies on graphene's exceptionally low heat capacity and its decoupled electron and phonon systems. I show in modeling that these thermal properties can lead to a GJJ photon detector for very low energy microwave photons. Experimentally, I show that a GJJ bolometer with its graphene weak link coupled to a microwave resonator can achieve an energy resolution equivalent to a single 32-GHz photon. The second detection mechanism reveals itself in the illumination of a GJJ with near-infrared light. I experimentally demonstrate single-photon detection in this system and show that the data is well fit by a model where photon-induced quasiparticles in the superconducting contacts cause the GJJ phase particle to escape. I give an overview of the single-photon, graphene, and Josephson-junction physics required to arrive at these results before presenting the experimental evidence for single-microwave-photon sensitivity and single-infrared-photon detection with the GJJ.