The quest to understand the nature of dark matter (DM) is one of the most important objectives of modern physics. To accomplish this ambitious goal, novel direct detection experiments have been proposed to test well-motivated DM candidates with unique phenomenology over many orders of magnitude in DM mass. To probe as much of DM parameter space as possible, this dissertation explores the detailed phenomenology of scalar ULDM in the 10−16 eV . mφ . 10−12 eV mass range at a new class of large-scale quantum sensors: atom interferometers. In particular, this thesis critically assesses the potential of atom interferometers as competitive probes of linearly-coupled scalar ULDM signals in three different regimes: large coupling, which will be accessible to small-scale experiments, small mass (i.e. mφ . 10−15 eV), which will be accessible to long-baseline terrestrial experiments, and high mass (i.e. mφ & 10−15 eV), which will be probed by all proposed terrestrial experiments. Firstly, by refining the calculation of the time-dependent signal induced by a linearly-coupled scalar ULDM in vertical atom gradiometers, we show that an experiment like AION-10, a compact 10 m gradiometer that will be operated in Oxford, can probe unexplored regions of DM parameter space characterised by large couplings to electrons and photons. Secondly, we perform the first detailed study of the reach of long-baseline atom interferometer experiments, such as km-long versions of AION and MAGIS, in the sub-Hz (i.e. mφ . 10−15 eV) regime, where the background is expected to be dominated by seismically-induced gravity gradient noise (GGN). We show that in certain geological settings GGN can be significantly mitigated when operating multiple networked interferometers, which we name a multigradiometer configuration. Finally, we study the phenomenology of the well-motivated high-frequency range of interferometers, which would be populated by signals affected by aliasing and related phenomena, including signal folding and spectral distortion. We demonstrate that accurate reconstruction of ULDM parameters can be achieved, thus paving the way for enhanced ULDM detection strategies with atom interferometers.
|Date of Award
|1 Dec 2023
|Christopher McCabe (Supervisor) & Diego Blas (Supervisor)