Evrim Yazgin
Cosmos science journalist
Quantum field theory suggests that the very structure of the universe could change, altering cosmos as we know it. A new quantum machine might help probe this elusive phenomenon, while also helping improve quantum computers.
True or false? It’s a life-or-death question
Nearly 50 years ago, quantum field theory researchers proposed that the universe exists in a “false vacuum”. This would mean that the stable appearance of the cosmos and its physical laws might be on the verge of collapse. The universe, according to this theory, could be transitioning to a “true vacuum” state.
The theory comes from predictions about the behaviour of the Higgs field associated with the Higgs boson, which Cosmos first looked at nearly a decade ago – the article is worth reading.
In short, like an electric or magnetic field, the Higgs field has a “potential” which determines its strength. Potential can be thought of like a cart on a rollercoaster. The higher the cart is on the rollercoaster track, the more potential energy it has.
The Higgs potential determines whether the universe is in a true vacuum state or a false vacuum state. A true vacuum is the lowest energy state and, therefore, stable. It’d be like the cart resting on a low, flat section of the rollercoaster track.
A false vacuum is like the cart getting stuck on a steep section of the track. A slight nudge could send the cart tumbling to a lower energy state.
If the universe is in a false vacuum, it is considered to be “metastable”. The metaphorical rollercoaster cart is neither tumbling nor resting in a true vacuum state.
What could happen
Measurements of the mass of the Higgs boson suggest that the universe is in a metastable state, waiting for something to push it out of the resting state.
An event with high enough energy could see a tiny region of the universe undergo “false vacuum decay.” This bubble would expand in all directions at the speed of light. Alternatively, quantum mechanics suggests that a particle could tunnel through to a true vacuum state.
Either way, the outcome would be lethal.
“We’re talking about a process by which the universe would completely change its structure,” says Zlatko Papic, a professor at the University of Leeds in the UK. “The fundamental constants could instantaneously change and the world as we know it would collapse like a house of cards.”
“What we really need are controlled experiments to observe this process and determine its timescales,” says Papic.
All it takes is a large quantum computer
Papic is the lead author of a paper published in Nature Physics which tackles this question.
The team used a machine to mimic the behaviour of bubbles in false vacuum. The bubbles are similar to liquid bubbles forming in water vapour.
The machine in question is a “quantum annealer” – a type of quantum computer which uses quantum fluctuations to optimise a process by finding the minimum of a given function or over a set of possible solutions.
“By leveraging the capabilities of a large quantum annealer, our team has opened the door to studying non-equilibrium quantum systems and phase transitions that are otherwise difficult to explore with traditional computing methods,” says first author Jaka Vodeb, from the Forschungszentrum Jülich research institute in Germany.
They placed 5,564 qubits into specific configurations that represent false vacuum and “triggered” a decay into true vacuum. The simulation is a 1-dimensional model, but the researchers think they’ll be able to perform 3-dimensional versions on the same annealer.
“It’s exciting to have these new tools that could effectively serve as a table-top ‘laboratory’ to understand the fundamental dynamical processes in the Universe,” Papic adds.
Beyond the potential to answer some of the most fundamental questions of the universe, the researchers say the outcome will help advance quantum computing. Understanding bubble interactions in the false vacuum could lead to improvements in error management in quantum systems and how they solve complex calculations.
“These breakthroughs not only push the boundaries of scientific knowledge but also pave the way for future technologies that could revolutionise fields such as cryptography, materials science, and energy-efficient computing,” says Vodeb.
