Photon-activated electron hopping in a single-electron trap enhanced by Josephson radiation

TL;DR

This study demonstrates photon-assisted electron tunneling in a single-electron trap using a Josephson junction interferometer as a microwave source, achieving high sensitivity and threshold operation at microwave frequencies.

Contribution

The paper introduces a novel method of photon-assisted tunneling detection using a Josephson junction interferometer, with high sensitivity and tunability at microwave frequencies.

Findings

High sensitivity to microwave photons with amplitudes around 10 nV.

Clear threshold behavior with an activation energy of approximately 400 μeV.

Effective detection at photon frequencies of 100-200 GHz.

Abstract

Using a Josephson junction interferometer (DC SQUID) as a microwave source for irradiating a single-electron trap, both devices fabricated on the same chip, we study the process of photon-assisted tunneling as an effective mechanism of single photon detection. High sensitivity down to a very small oscillation amplitude $v_{\rm J} \sim$ 10 nV$\ll E_{\rm act} \lesssim hf_{\rm J}$ and down to low photon absorption rates $\Gamma_{\rm ph} \sim$ (1--50)Hz, as well as a clear threshold type of operation with an activation energy $E_{\rm act} \sim$ 400 $\mu$eV, are demonstrated for the trap with respect to the microwave photons of frequency $f_{\rm J} \sim$ (100--200)GHz. Tunable generation is demonstrated with respect to the power and frequency of the microwave signal produced by the SQUID source biased within the subgap voltage range. A much weaker effect is observed at the higher junction voltages along the quasiparticle branch of the $I-V$ curve; this response mostly appears due to the recombination phonons.