Microwave squeezing represents the ultimate sensitivity frontier for superconducting qubit measurement. However, observation of enhancement has remained elusive, in part because integration with conventional dispersive readout pollutes the signal channel with antisqueezed vacuum. Here we induce a stroboscopic light-matter coupling with superior squeezing compatibility, and observe an increase in the room-temperature signal-to-noise ratio of 24%. Squeezing the orthogonal phase controls measurement backaction, slowing dephasing by a factor of 1.8. This protocol enables the practical use of microwave squeezing for qubit state measurement.
@article{arxiv.1708.01674,
title = {Stroboscopic qubit measurement with squeezed illumination},
author = {Andrew Eddins and Sydney Schreppler and David M. Toyli and Leigh S. Martin and Shay Hacohen-Gourgy and Luke C. G. Govia and Hugo Ribeiro and Aashish A. Clerk and Irfan Siddiqi},
journal= {arXiv preprint arXiv:1708.01674},
year = {2018}
}