Demonstration of Improved Sensitivity in Recovering a Displaced Cavity State with Josephson Parametric Amplifiers

Josephson parametric amplifiers (JPAs) can efficiently generate and amplify squeezed microwave light [1], useful in improving the measurement of the state of a resonant cavity. If deployed in a cavity-based search for dark matter axions, squeezing is capable of accelerating the search by increasing the signal-to-noise ratio of the microwave photons generated from axion conversion, over a broad bandwidth [2]. In a demonstration of this, we operate a pair of JPAs, flux-pumped to minimize microwave losses, with an overcoupled, empty cavity placed between them. Into this cavity, we inject a microwave tone through a separate, weakly-coupled port, and observe that squeezing significantly enhances this signal’s visibility.

[1] Mallet, F. et al. Phys. Rev. Lett. 106, 220502 (2011).
[2] Zheng, H. et al. preprint arXiv:1607.02529 (2016).