We introduce a microwave bolometer aimed at high-quantum-efficiency detection of wave packet energy within the framework of circuit quantum electrodynamics, the ultimate goal being single microwave photon detection. We measure the differential thermal conductance between the detector and its heat bath, obtaining values as low as 5 fW/K at 50 mK. This is one tenth of the thermal conductance quantum and corresponds to a theoretical lower bound on noise-equivalent-power of order 10−20W/\mboxHz at 50 mK. By measuring the differential thermal conductance of the same bolometer design in qualitatively different environments and materials, we determine that electron--photon coupling dominates the thermalization of our nanobolometer.
@article{arxiv.1403.6586,
title = {Microwave nanobolometer based on proximity Josephson junctions},
author = {J. Govenius and R. E. Lake and K. Y. Tan and V. Pietilä and J. K. Julin and I. J. Maasilta and P. Virtanen and M. Möttönen},
journal= {arXiv preprint arXiv:1403.6586},
year = {2014}
}