Abstract
In cavity-based axion dark matter detectors, quantum noise remains a primary barrier to achieving the scan rate necessary for a comprehensive search of 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 amplification 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 that this technique can increase the scan rate up to 15-fold relative to the scan rate of a detector limited by vacuum noise.
- Received 9 July 2021
- Accepted 22 October 2021
- Corrected 5 January 2022
DOI:https://doi.org/10.1103/PRXQuantum.2.040350
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Corrections
5 January 2022
Correction: A conversion error caused a term to drop out in Equation (2) and has been fixed.
Popular Summary
The axion is a hypothetical particle that could account for some or all of the dark-matter content of the universe. However, because the mass of the axion is unknown, axion detectors must search a vast parameter space. Even with noise reduced to the level of quantum fluctuations, the rate at which existing detectors can scan through the space of possible axion masses is prohibitively low. Recent work shows it possible to reduce noise below the level of quantum fluctuations by way of squeezing and thereby double the scan rate compared to a quantum-limited detector; however, further scan rate enhancement is inhibited by component losses. In this work, we propose a quantum-enhanced measurement technique that is robust against such component losses and is capable of increasing the detector scan rate by a factor of up to 15.
Our method achieves this scan rate enhancement using a specific interaction between an axion-sensitive electromagnetic cavity and a second auxiliary resonator. With analytical models of this system, we show that this interaction can amplify the signal and noise emerging from the cavity relative to the noise introduced by measurement. This amplification widens the bandwidth of sensitivity, allowing the detector to scan more possible axion masses at a time. Through numerical modeling, we then predict the scan rate enhancement achievable in a realistic implementation of this method.
Successful experimental implementation of this concept would dramatically accelerate the search for axion dark matter.
