Vaartjes Arjen, Kringhøj Anders, Vine Wyatt, Day Tom, Morello Andrea, Pla Jarryd J
School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, NSW 2052, Australia.
Nat Commun. 2024 May 18;15(1):4229. doi: 10.1038/s41467-024-48519-3.
Squeezed states of light have been used extensively to increase the precision of measurements, from the detection of gravitational waves to the search for dark matter. 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 make squeezing vacuum noise an exceptionally difficult task. Here we demonstrate direct measurements of high levels of microwave squeezing. We use an ultra-low loss setup and weakly-nonlinear kinetic inductance parametric amplifiers 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 large 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. These results enable experiments that combine squeezing with magnetic fields and permit quantum-limited microwave measurements at elevated temperatures, significantly reducing the complexity and cost of the cryogenic systems required for such experiments.
压缩光态已被广泛用于提高测量精度，从引力波探测到暗物质搜寻。在光学领域，由于存在低损耗光学元件和高性能压缩器，实现高水平的真空噪声压缩是可能的。然而，在微波频率下，压缩器件的局限性以及微波元件的高插入损耗使得压缩真空噪声成为一项极其困难的任务。在此，我们展示了对高水平微波压缩的直接测量。我们使用超低损耗装置和弱非线性动态电感参量放大器将微波噪声压缩至比真空水平低7.8(2)分贝。这些放大器对磁场具有抗性，并允许在高达2特斯拉的磁场中展示大压缩水平。最后，我们利用放大器的高临界温度来压缩热环境，在1.8开尔文的温度下实现真空水平噪声。这些结果使得能够开展将压缩与磁场相结合的实验，并允许在较高温度下进行量子极限微波测量，显著降低此类实验所需低温系统的复杂性和成本。
