Abstract
We consider the use of quantum-limited mechanical force sensors to detect ultralight (sub-meV) dark matter (DM) candidates which are weakly coupled to the standard model. We show that mechanical sensors with masses around or below the milligram scale, operating around the standard quantum limit, would enable novel searches for DM with natural frequencies around the kHz scale. This would complement existing strategies based on torsion balances, atom interferometers, and atomic clock systems.
Highlights
We consider the use of quantum-limited mechanical force sensors to detect ultralight dark matter candidates which are weakly coupled to the standard model
We propose ultralight DM detection as a nearer-term goal achievable with just a few mechanical sensors, operating at noise levels around the “standard quantum limit” (SQL), a benchmark already demonstrated in many devices
The scalable nature of an array and potential improvements to the noise levels beyond the SQL would allow for significant ultralight DM detection reach en route to the long-term goal of gravitational DM detection with mechanical sensors
Summary
We briefly review the salient facts about ultralight dark matter. The essential feature of these ultralight candidates is that they behave as a persistent, wave-like field, due to their high occupation number. Bosonic dark matter is required to have mφ 10−22 eV so that its de Broglie wavelength does not exceed the core size of a dwarf galaxy and to satisfy Lyman-α constraints [7, 34,35,36] (note that recent evidence indicates that the constraints may be a few orders of magnitude stronger than this [36,37,38]). For any mφ 0.1 eV, this occupancy is huge, indicating that the dark matter can be treated as a classical field, essentially a superposition of many different plane waves. These waves have velocities following a Boltzmann distribution. We briefly exhibit a pair of DM models to show how this type of signal arises
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