HeLIOS: The Superfluid Helium Ultralight Dark Matter Detector with Optomechanical Transducer

Cavity optomechanical systems can probe the motion of a mechanical oscillator with unprecedented sensitivity, providing the opportunity to search for new physics. If dark matter (DM) contains ultralight bosonic particles, they would behave as a classical wave and manifest through an oscillating force on baryonic matter that is coherent over ∼10⁶ periods^1,2. Our Helium ultraLIght dark matter Optomechanical Sensor (HeLIOS) utilizes the high-Q acoustic modes of superfluid helium-4 to resonantly amplify this signal to displacements larger than thermal motion at millikelvin temperatures, which can be read out through a superconducting re-entrant microwave cavity as sensitive optomechanical transducer³. Pressurizing the helium allows for the unique possibility of tuning the mechanical frequency and broadening the DM detection bandwidth. The first-generation HeLIOS detector could explore unconstrained parameter space for both scalar and vector ultralight DM after a few minutes of integration time^4,5.

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