Hunting for exotic bosons with flying quantum sensors in space

Numerous theories beyond the standard model predict the existence of exotic bosons that could serve as candidates for dark matter. Here we present the Space-based Quantum Sensing for Interaction and Exotic Bosons Research Exploration scheme, along with a demonstration of a prototype space quantum sensor designed for near-future space experiments. The core concept involves probing exotic-boson-mediated spin-spin-velocity interactions between the spins within space quantum sensors and the electrons within the Earth. Unlike terrestrial counterparts, our space-based searches benefit from the significantly increased velocity provided by the orbital motion of the space quantum sensors around the Earth, which approaches the first cosmic speed. Additionally, the substantial abundance of polarized electrons within the Earth also enhances the scope of our mission. We demonstrate that our prototype space quantum sensor can suppress geomagnetic interference in space by 12 orders of magnitude, achieving a single-shot sensitivity of 4.3 fT in the sub-mHz regime. This illustrates the feasibility of conducting exotic-boson searches in the challenging space environment. As a result, the search sensitivity for such exotic interactions can be significantly enhanced by up to approximately 7 orders of magnitude compared to both terrestrial experiments and proposals. This work opens up a novel approach for searching for new physics, including space-based axion-halo searches and $CPT$ violation probes.