We have embedded a small Josephson junction in a microwave resonator that allows simultaneous dc biasing and dispersive readout. Thermal fluctuations drive the junction into phase diffusion and induce a temperature-dependent shift in the resonance frequency. By sensing the thermal noise of a remote resistor in this manner, we demonstrate primary thermometry in the range from 300 mK to below 100 mK, and high-bandwidth (7.5 MHz) operation with a noise-equivalent temperature of better than 10 μK/Hz. At a finite bias voltage close to a Fiske resonance, amplification of the microwave probe signal is observed. We develop an accurate theoretical model of our device based on the theory of dynamical Coulomb blockade.
@article{arxiv.1604.05089,
title = {Dispersive thermometry with a Josephson junction coupled to a resonator},
author = {O. -P. Saira and M. Zgirski and K. L. Viisanen and D. S. Golubev and J. P. Pekola},
journal= {arXiv preprint arXiv:1604.05089},
year = {2016}
}
Comments
(v2) Added data on high-power readout; Reformatted and restructured main text; Language and typographical fixes