Strong Microwave Squeezing Above 1 Tesla and 1 Kelvin*

Squeezed states of light have been used extensively to increase the precision of measurements, from the detection of gravitational waves [1] to the search for dark matter [2, 3]. In the optical domain, high levels of vacuum noise squeezing are possible due to the availability of low loss optical components and high-performance squeezers. At microwave frequencies, however, limitations of the squeezing devices and the high insertion loss of microwave components makes squeezing vacuum noise an exceptionally difficult task. Here we demonstrate a new record for the direct measurement of microwave squeezing. We use an ultra-low loss setup and weakly-nonlinear kinetic inductance parametric amplifiers [4] to squeeze microwave noise 7.8(2) dB below the vacuum level. The amplifiers exhibit a resilience to magnetic fields and permit the demonstration of record squeezing levels inside fields of up to 2 T. Finally, we exploit the high critical temperature of our amplifiers to squeeze a warm thermal environment, achieving vacuum level noise at a temperature of 1.8 K.

[1] J. Aasi, et al. Nature Photonics, 7(8):613–619 (2013)

[2] M Malnou, et al. Phys. Rev. X, 9(2):021023 (2019)

[3] K. M. Backes et al. Nature, 590(7845):238-242 (2021)

[4] D. J. Parker et al. Phys. Rev.Applied, 17:034064 (2022)