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Cavity Entanglement and State Swapping to Accelerate the Search for Axion Dark Matter



K. Wurtz, B.M. Brubaker, Y. Jiang, Elizabeth Ruddy, Dan Palken, Konrad Lehnert


In cavity-based axion dark matter detectors, quantum noise remains a primary barrier to achieving the scan rate necessary for a comprehensive search of the axion parameter space. Here we introduce a method of scan rate enhancement in which an axion-sensitive cavity is coupled to an auxiliary resonant circuit through simultaneous two-mode squeezing (entangling) and state swapping interactions. We show analytically that when combined, these interactions can amplify an axion signal before it becomes polluted by vacuum noise introduced by measurement. This internal ampli cation yields a wider bandwidth of axion sensitivity, increasing the rate at which the detector can search through frequency space. With interaction rates predicted by circuit simulations of this system, we show this technique can increase the scan rate up to 15-fold relative to the scan rate of a detector limited by vacuum noise.
Physical Review X


dark matter, quantum enhanced sensing, quantum squeezing


Wurtz, K. , Brubaker, B. , Jiang, Y. , Ruddy, E. , Palken, D. and Lehnert, K. (2021), Cavity Entanglement and State Swapping to Accelerate the Search for Axion Dark Matter, Physical Review X, [online],, (Accessed May 19, 2024)


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Created December 10, 2021, Updated November 29, 2022