The breakthrough experiment was conducted in Trento (Italy) by researchers of the University of Trento, from the Italian National Institute of Optics CNR-INO and from TIFPA, with theory support from Newcastle University.

In quantum field theory, when a not-so-stable state transforms into the true stable state, it's called "false vacuum decay." This happens through the creation of small localised bubbles. While existing theoretical work can predict how often this bubble formation occurs, there hasn’t been much experimental evidence. Now, an international research team involving Newcastle University scientists has for the first observed these bubbles forming in carefully controlled atomic systems. Published in the journal Nature Physics, the findings offer experimental evidence of bubble formation through false vacuum decay in a quantum system.

The findings are supported by both theoretical simulations and numerical models, confirming the quantum field origin of the decay and its thermal activation, opening the way to the emulation of out-of-equilibrium quantum field phenomena in atomic systems.

An experiment conducted in Trento (Italy) by researchers of the University of Trento,from the Italian National Institute of Optics CNR-INO and from TIFPA, uses a supercooled gas at a temperature of less than a microkelvin (one millionth of a degree) from absolute zero. At this temperature, bubbles are seen to emerge as the vacuum decays and the Newcastle University’s Professor Ian Moss and Dr Tom Billam were able to show conclusively that these bubbles are a result of thermally activated vacuum decay.

Ian Moss, Professor of Theoretical Cosmology at Newcastle University’s School of Mathematics, Statistics and Physics, said: “Vacuum decay is thought to play a central role in the creation of space, time and matter in the Big Bang, but until now there has been no experimental test. In particle physics, vacuum decay of the Higgs boson would alter the laws of physics, producing what has been described as the `ultimate ecological catastrophe’.”

Dr Tom Billam, Senior Lecturer in Applied Maths/Quantum, added: "Using the power of ultracold atom experiments to simulate analogs of quantum physics in other systems - in this case the early universe itself - is a very exciting area of research at the moment."

The research opens up new avenues in the understanding of early universe, as well as ferromagnetic quantum phase transitions.

This groundbreaking experiment is only the first step in exploring vacuum decay. The ultimate goal to is find vacuum decay at the temperature of absolute zero where the process is driven purely by quantum vacuum fluctuations. An experiment in Cambridge, supported by Newcastle as part of a national collaboration QSimFP, aims to do just this.

This research was funded by Provincia Autonoma di Trento, INFN, MUR, Q@TN, UK Quantum Technologies programme and European Union.

Reference

Zenesini, A., Berti, A., Cominotti, R. et al. False vacuum decay via bubble formation in ferromagnetic superfluids. Nat. Phys. (2024). https://doi.org/10.1038/s41567-023-02345-4