Quantum enhanced sensing for axion dark matter through three-wave mixing*

Recent demonstrations show that a weak microwave tone at an unknown frequency can be found more rapidly by using squeezed microwave fields and single quadrature measurement. In particular this squeezed-state receiver arrangement increases the bandwidth of the measurement apparatus. This technique has been successfully applied in the search for axionic dark matter, where it yielded a factor of two increase in search rate compared to the quantum-noise-limited value. In order to further improve the search rate, we propose a method to increase the visibility bandwidth which involves dynamically varying the coupling of an axion sensitive microwave cavity to an auxiliary readout resonator using Josephson ring modulator (JRM) or related device. By varying the coupling at the sum and difference frequencies of the two modes, simultaneous exchange and amplification processes should yield a 15-fold increase in the search rate. In this talk, I will discuss the theoretical foundation for this search method and progress towards a prototype experiment.