We perform state tomography of an itinerant squeezed state of the microwave field prepared by a Josephson parametric amplifier (JPA). We use a second JPA as a pre-amplifier to improve the quantum efficiency of the field quadrature measurement (QM) from 2% to 36 +/- 4%. Without correcting for the detection inefficiency we observe a minimum quadrature variance which is 69 +/- 8% of the variance of the vacuum. We reconstruct the state's density matrix by a maximum likelihood method and infer that the squeezed state has a minimum variance less than 40% of the vacuum, with uncertainty mostly caused by calibration systematics.
@article{arxiv.1012.0007,
title = {Quantum state tomography of an itinerant squeezed microwave field},
author = {F. Mallet and M. A. Castellanos-Beltran and H. S. Ku and S. Glancy and E. Knill and K. D. Irwin and G. C. Hilton and L. R. Vale and K. W. Lehnert},
journal= {arXiv preprint arXiv:1012.0007},
year = {2012}
}
Comments
8 pages, 5 figures, published version to contain higher resolution figures