King's College London

The approach produces a ‘quantum tornado’ of superfluid helium particles in the lab that replicates the gravitational conditions near rotating black holes.

Published today in Nature, the method provides a solution to studying black holes up close in the lab. Previously, the only way to study these mysterious phenomena has been to observe their effect on surrounding matter in Space, such as using the Event Horizon Telescope to survey a black hole’s environment through radio waves to build up an image of their structure.

Funded by a £5 million grant from the Science Technology Facilities Council, the research was undertaken by Professor Ruth Gregory, Professor of Theoretical Particle Physics at King’s alongside the University of Nottingham and five other UK institutions.  

To create black holes in the lab, the team built a quantum simulator – a tool that probes the quantum properties of particles - by mixing superfluid helium with a spinning propeller. Superfluid has zero viscosity and flows without friction, and when stirred they forms vortices that continue to rotate indefinitely. In this experiment, the quantum tornado of swirling helium begins exhibiting unusual quantum properties, mimicking the gravitational conditions near rotating black holes.

Professor Silke Weinfurtner from the University of Nottingham is leading the work in the Black Hole Laboratory where this experiment was developed. She said, “When we first observed clear signatures of black hole physics in our initial experiment in 2017, it was a breakthrough moment for understanding some of the bizarre phenomena that are often challenging, if not impossible, to study otherwise.”

King’s Post Doctoral Researcher Sam Patrick, who worked on the modelling for the experiments said, “Since our original experiment we’ve been working to develop better theoretical models for describing analogue black holes. This new platform allowed us to test these models with unprecedented accuracy and show how they work well, which is exciting.”

The previous experiment used a specially designed water bath to attempt to simulate the conditions around a black hole. Superfluid helium has a viscosity 500 times lower than water.

Modern physics is built on two re fundamentally incompatible theories – while General Relativity explains gravity as the curvature of space-time caused by mass and energy, Quantum Field Theory explains it, and all forces as interactions between particles in the universe.

For Professor Ruth Gregory this experiment aims to test these ideas that underlie our understanding of space, time and matter. She said, “our project aims to build laboratory experiments that simulate the aspects of the nature of the vacuum and the nature of space/time. We want to test methods that are simply beyond our direct ability to access.

“Finding a way to explore these contradictions between general relativity and quantum fiel theory in the lab, gives us a new tool to test speculative proposals in a controlled setting.”

While Einstein’s General Relativity successfully describes the region of a black hole, the researchers want to find a more quantum description for the phenomena to find a correlation between the two theories. One of the foundational features of quantum mechanics is that things come in packets. For example, energy comes in multiples of a fundamental quantum or the spin of a particle.

Professor Gregory said, “using the liquid helium black hole vortex simulator, we hope to find evidence of the quantisation in the ringing of the ‘black hole’ that could give insight into how the quantum nature of gravitational black holes emerges.”

Through the experiment, researchers uncovered parallels between the vortex flow and the gravitational influence of black holes on the surrounding spacetime. This achievement opens new avenues for simulations of finite-temperature quantum field theories within the complex realm of curved spacetimes.