We demonstrate fast and ultrasensitive charge detection with a cavity-embedded Cooper pair transistor (cCPT) via dispersive readout of its Josephson inductance. We report a minimum charge sensitivity of 14μe/Hz with a detection bandwidth on the order of 1 MHz using 16 attowatts of power, corresponding to the single-photon level of the cavity. In addition, our measured sensitivities are within a factor of 5 of the quantum limit for this device. The single-photon-level sensitivity of the cCPT is comparable to that of the rf-SET, which typically operates using picowatts of power corresponding to hundreds of thousands of photons in its tank circuit. Our results support the feasibility of using the cCPT to mediate an optomechanical interaction that reaches the single-photon strong coupling regime.
@article{arxiv.2102.05362,
title = {Fast and Ultrasensitive Electrometer Operating at the Single-Photon Level},
author = {B. L. Brock and Juliang Li and S. Kanhirathingal and B. Thyagarajan and M. P. Blencowe and A. J. Rimberg},
journal= {arXiv preprint arXiv:2102.05362},
year = {2021}
}