Quantum Sensing Techniques for DMRadio-50L

Haloscope experiments designed to detect the QCD axion require sensitivity to a small power signal that is easily buried in the noise fluctuations of a measurement. The DMRadio-50L experiment will be a testbed for new quantum sensing techniques that aim to increase the experiment's sensitivity to an axion signal. Low frequency axion searches are ideal for specific, unique strategies to achieve improved noise performance. One such strategy is to manipulate the relative contributions of quantum measurement noise in the detector. Achieving noise performance beyond the Standard Quantum Limit is important for the long term success of the DM Radio program. To this end, the DM Radio collaboration is dedicated to developing such techniques. Two techniques that will be emphasized in this talk are the use of Radiofrequency Quantum Upconverters (RQUs) and Bode-Fano evasion via active devices. RQUs provide a mechanism for backaction evasion through a phase-sensitive measurement, and Bode-Fano evasion via active devices would allow for broadband measurements with the receiver chain.