Detection of gravitational waves and dark matter using atom interferometry (MAGIS-100)

The successful detection of gravitational waves (GWs), originating from a binary black hole merger, by the Laser Interferometer GW Observatory (LIGO), in 2015, not only opened a new window into the universe, but also inspired complementary GW detection schemes using a multitude of quantum technologies. One such technology is atom interferometry. This talk discusses recent progress toward the design and construction of a 100 m baseline atom interferometer (AI) at Fermilab. AIs like these would, in principle, enable detection of not only GWs in the low-frequency band (0.03-3 Hz), but also certain classes of ultralight dark matter (ULDM).

Crudely, the operating principle of the AI can be thought of as using a pair of vertically separated optical atomic clocks (OACs) to measure changes in the light propagation time, Δt = ΔL/c, across a baseline of length L, where c is the speed of light. Therefore, sensitivity to GW-induced strain, ΔL/L, is proportional to L. For the AI discussed here, an L = 100 m baseline is used as a development platform, with the ultimate goal of L to be on the kilometer-scale. The latter is expected to be sensitive to known GW sources. This instrument, known as Matter-wave Atomic Gradiometer Interferometric Sensor (MAGIS), derives its sensitivity in its target band due to the fact that the atoms, which comprise the OAC, are under free fall; thus effectively decoupling them from seismic noise.

Furthermore, since the laser light, traveling across the baseline, is resonant with an atomic transition, the phase (ϕ) extracted from the atomic interference depends not only on the light propagation time (t), but also the resonance frequency (ω) as ϕ = ωt. Certain ULDM models predict oscillation of ω at the dark matter Compton frequency. Therefore, MAGIS-100 can be alternatively used to perform ULDM searches with unprecedented sensitivity for ULDM masses corresponding to the 0.03-3 Hz band.