Constraining ultralight dark matter through an accelerated resonant search

Typical weak signal search experiments rely on resonant effects, where the resonance frequency is scanned over a broad range, resulting in significant time consumption. In this study, we demonstrate an accelerated strategy that surpasses the typical resonance-bandwidth limited scan step without compromising sensitivity. We apply this method to an alkali-noble-gas spin system, achieving an approximately 30-fold increase in scanning step size. Additionally, we obtain an ultrahigh sensitivity of 1.29 fT ⋅ Hz −1/2 at around 5 Hz, corresponding to an energy resolution of approximately 1.8 × 10 −23 eV ⋅ Hz −1/2 , which is among the highest quantum energy resolutions reported. Furthermore, we use this sensor to search for axion-like particles, setting stringent constraints on axion-like particles (ALPs) in the 4.5–15.5 Hz Compton-frequency range coupling to neutrons and protons, improving on previous limits by several-fold. This accelerated strategy has potential applications in other resonant search experiments. Weak signal detection, as in the case for the search of Dark Matter, relies on the resonant effect, when many frequencies are scanner in search of the signal, but this is very time consuming. The authors present a magnetometry method that combines high sensitivity and a wider parameter space coverage adopting an artificially enlarged resonance width, increasing the scanning efficiency.