Although dark matter accounts for 85% of the matter in our Universe, its nature is a mystery. Dark matter is likely passing through our laboratories on Earth unnoticed, leaving faint traces that are challenging to measure. We are developing quantum sensors to hunt for these traces and gain crucial insight into dark matter.

We use mechanical oscillators to search for dark matter¹. Dark matter particles passing by would cause the mechanical oscillators to experience occasional kicks. We will precisely monitor the mechanical oscillators and hunt for such events.

If dark matter is instead wave-like in nature, it will drive oscillatory motion of the mechanical oscillators, and we will also probe this effect.

Each of our mechanical oscillators consists of a magnetically-levitated superconductor. Levitated superconductors are well suited for dark matter searches:

• The motion of levitated superconductors can be precisely monitored using superconducting quantum circuits^2-4. We leverage on advances that are being made with superconducting quantum computers.
• The motion of levitated superconductors can be highly isolated from noise sources²; the superconductors are levitated within a stable trap, far from other surfaces, in ultrahigh vacuum, at extremely low temperatures around 10mK, within magnetic shielding, and isolated from external vibrations.

Levitated superconductors are also used as gravimeters⁵ and gravity gradiometers⁶, and this platform is being developed for probing quantum physics with large masses^2-4,7.

In the near term we will search for dark matter via its theorized non-gravitational interactions with ordinary matter^8,9. Astrophysical and cosmological observations guarantee that the gravitational interaction between dark matter and ordinary matter exists. Our long-term goal is to hunt for dark matter through its gravitational interaction, which would be a unique approach - since all existing laboratory searches rely on the existence of stronger, non-gravitational interactions. A gravity-based search is challenging because gravity is much weaker than the other fundamental forces.

Our vision is to build a 3D meter-scale array that is densely packed with mechanical sensors^10,11. When a dark matter particle passes through the array, its gravitational pull excites the sensors it passes close to, and it will leave a 1D track of excited sensors within the 3D array. For this search the individual sensors will need to be precisely monitored using quantum sensing techniques. Magnetically-levitated superconductors make the ideal platform for building this detector.

We will build our detector in the heart of Vienna at the Institute for High Energy Physics (HEPHY) of the Austrian Academy of Sciences (OeAW). This is an ideal location for this project, which applies quantum sensing to astroparticle physics:

• HEPHY has strong expertise in conducting dark matter searches and in dark matter theory. It is part of several international particle physics collaborations.
• Vienna is a prominent hub for cutting-edge research in quantum physics.