A quantum-enhanced search for dark matter axions

In dark matter axion searches, quantum uncertainty manifests as a fundamental noise source, limiting the measurement of the quadrature observables used for detection. We use vacuum squeezing to circumvent the quantum limit in a search for a new particle. By preparing a microwave-frequency electromagnetic field in a squeezed state and near-noiselessly reading out only the squeezed quadrature, we double the search rate for axions over a mass range favored by recent theoretical projections. We observe no signature of dark matter axions in the combined $16.96-17.12$ and $17.14-17.28\mu \text{eV}\mathrm{/}{c}^2$ mass window for axion-photon couplings above $g_{\gamma }=1.38\times g_{\gamma }^{\text{KSVZ}}$, reporting exclusion at the 90% level.