A vat of superfluid helium-3, cooled to 100 microkelvin above absolute zero, will serve as both a dark matter detector and a miniature model of the early universe. The problem is that decades of searches for heavy dark matter particles have come up empty, and the leading theory of phase transitions predicts no gravitational waves from the early cosmos—yet space missions like LISA are being built to look for them. This project tackles both gaps simultaneously. It will hunt for dark matter particles with masses below that of a proton, a range largely unexplored, while using controlled phase transitions in the quantum fluid to test whether the Standard Model’s predictions about the early universe are correct. This is fundamental science with no immediate practical application. The payoff is understanding: either confirming or ruling out key ideas about how structure formed in the universe and why matter dominates over antimatter. Past fundamental research on superfluids and quantum sensors has led to breakthroughs in precision measurement and navigation technology, but those are not the goals here. The primary impact will be on cosmology and particle physics, helping to interpret data from future gravitational wave observatories and shaping the next generation of dark matter experiments.
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The QUEST-DMC programme seeks to answer some of the most fundamental questions facing modern physics: What is the physics of the early universe? What is the nature of dark matter? What is the origin of the matter-antimatter asymmetry? We will focus on the investigation of two core building blocks of early universe cosmology, which may be fundamentally linked; the identity and nature of dark matter and the physics of phase transitions. By combining a macroscopic quantum system, superfluid helium-3 (3He), with state-of-the-art quantum technologies we will pioneer a new dark matter search experiment with unprecedented discovery potential. In parallel we will use the unique properties of superfluid 3He as a quantum simulator of phase transitions in the early universe. Dark Matter plays a vital role in the evolution of the universe, for example, it played a central role in the formation of structure in early universe and today plays a key role in stopping galaxies flying apart. The focus of dark matter studies and searches to date has been on Weakly Interacting Massive Particles (WIMPs) whose predicted mass range is broadly speaking between 10-1000 times that of the proton. The direct, indirect and collider searches for this dark matter candidate to date have been extensive but ultimately unsuccessful. There is a strong motivation to widen the search. The fact that the universe only consists of matter with no anti-matter requires explanation, since it is reasonable to assume that matter and anti-matter were produced in equal quantities in the Big Bang. This implies that during the evolution of the universe a process took place that dynamically generated the asymmetry between matter and anti-matter. Models linking the dynamics of dark matter with the generation of the matter/anti-matter asymmetry naturally predict a mass scale of dark matter that is close to the mass of the proton, of order 1 GeV/c2, suggesting an alternative target mass range to the standard WIMP. This project will create and operate a detector for the direct search of dark matter with sub-GeV masses using superfluid helium-3 as a target with world-leading sensitivity. The second major component of this project is a detailed investigation of the physics of phase transitions. Phase transitions are a key prediction of the symmetry-breaking paradigm of the Standard Model of particle physics in extreme conditions, such as those of the early universe or inside neutron stars. A first-order phase transition produces a characteristic gravitational wave signature and forms a leading motivation for gravitational wave searches. According to our current understanding of the mechanism of phase transitions, called nucleation theory, no gravitational waves are predicted in Standard Model. If gravitational waves are detected and their origins can be linked to a phase transition in the early universe then this would be evidence of Physics beyond the Standard Model of particle physics, with high impact on our understanding of fundamental physics. It is critical that the physics of phase transitions is tested so that experiments such as the approved European Space Agency mission LISA due for launch in 2034 are fully exploited. This project will do this using phase transitions between different quantum vacua in superfluid 3He, under controlled conditions, as a quantum analogue. This programme brings together the frontiers of cosmology, ultralow temperatures and quantum technology. Both experiments exploit the unique properties of superfluid helium-3, cooled to 100 microkelvin above absolute zero. It will rely on a range of state-of-the-art superconducting quantum sensors, and nanofabricated structures such as nanobeam resonators, and structured nanoscale confinement. Future developments in quantum technologies will generate further improvements in sensitivity and range of the sub-GeV dark matter search in the longer term.
Andrew Casey (Principal Investigator)Jocelyn Monroe (Co-Investigator)John Saunders (Co-Investigator)Stephen West (Co-Investigator)Xavier Rojas (Co-Investigator)
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