DC measurement of dressed states in a coupled 100~GHz resonator system using a single quasiparticle transistor as a sensitive microwave detector

TL;DR

This paper demonstrates on-chip microwave detection at around 100GHz using a superconducting single-electron transistor, revealing dressed states in a coupled resonator system with high sensitivity but limited strong coupling.

Contribution

It introduces a novel microwave detection technique employing a superconducting single-electron transistor to observe dressed states in a high-frequency cQED system.

Findings

Detected dressed states via anticrossing in a 100GHz resonator system

Achieved high microwave sensitivity with low photon population detection

Observed wide frequency splitting corresponding to Jaynes-Cummings coupling

Abstract

We report on the on-chip detection of microwaves in the frequency range around 100GHz. For the purpose of detection, we employ a discrete transport channel triggered in a superconducting single-electron transistor by photon-assisted tunneling of quasiparticles. The technique is successfully applied to observe the spectrum of the dressed states of a model cQED system consisting of a superconducting coplanar resonator coupled to a quantum Josephson oscillator. The dressed states appear as typical resonance anticrossing exhibiting, in our case, an expectedly wide frequency splitting corresponding to the Jaynes-Cummings coupling strength, g/pi~10GHz. Due to the high decay rate, gamma~20-40GHz, in the very transparent Josephson junctions used, the strong coupling limit, g>>gamma, which is required for qubit operation, is not achieved, and the photon population in the resonator is low, <n>~1. Remarkably, the continuous readout of the low population states demonstrates the high microwave sensitivity of the detector.