February 16, 20254 min readQuantum Simulation Shows How Universe-Destroying Bubbles Could GrowPhysicists are finding new ways to model false vacuum decay, a terrifying, albeit remote, cosmic endgameBy Dan Garisto edited by Lee Billings Nico Korbel/Getty ImagesThe good news is that you, and everyone you love, will die long before it might happen.Now for the bad news. Someday, in the far-distant future, eons beyond its 13.8-billion-year adolescence, the universe could suffer a false vacuum decay. This would involve a bubble of incomprehensibly destructive power that would spontaneously materialize and ripple through spacetime at the speed of light. Such an event would rewrite the fundamental laws of physics and obliterate our reality in the equivalent of a cosmic cut-and-paste command.Whatever [was] in the false vacuumso this would be uswould disappear immediately right when this bubble spread through us, says Jaka Vodeb, a physicist at the Jlich Center in Germany.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.For decades, theoretical physicists have wondered whether the universe is stable or metastable. In the latter scenario, it is in afalse vacuum that will eventually decay to a state of lower energy, a true vacuum. Vacuum, in this case, refers neither to an appliance nor to outer space but to a state of truly empty space, which can still have energy even when it is devoid of particles. In recent years theorists experimental colleagues have begun tinkering with quantum systems to whip up analogous systems in the lab (given that working with bona fide universe-annihilating bubbles would be a bit dicey).Earlier this month Vodeb and his colleagues published the findings of their cosmic bubble simulation in Nature Physics. Using a 5,564-qubit quantum annealer from the company D-Wave to essentially create a one-dimensional chain of highly sensitive magnets that could point up or down, they simulated the growth and interactions of cosmic bubbles.The researchers first arranged the qubits to point up and then tuned a magnetic field so that pointing down was energetically favorable. Over time, some qubits flipped to point down, and the flips cascaded to nearby qubits, forming clusters, or bubbles. The analogue bubbles then grew and merged, matching predictions about their cosmic counterparts. The results, first shared on the preprint server arXiv.org in June 2024, represent the first time cosmic bubble interactions have been simulated.This is one of the simplest demonstrations of how a vacuum can decay in a real, physical system with a proper analytical theory behind it, says Roopayan Ghosh, a theorist at University College London, who was a peer reviewer for the paper. Thats why I think people should find it interesting.Contrary to their apocalyptic subject matter, the physicists who study false vacuum decay are rather zen about the whole thing. I dont really, you know, live in existential fear, Vodeb says.So Long, and Thanks for All the Flash-Frozen FishTo understand the metastability of the false vacuum, start by filling a bottle with distilled water and putting it in your freezer for a couple of hours. The bottles water, free of dust or chemicals to trigger crystallization into ice, can remain liquid below the normal freezing point. This is a metastable state. Jostling the bottle will cause the supercooled water to immediately freeze to ice, shifting to its stable state.Another example of metastability, more morbidly apropos of universe-ending bubbles, involves fish.The Greenland cod (Gadus ogac) is a tan-colored fish thats uninterestingsave for the fact that its blood freezes at about 0.7 degree Celsius. During the winter, seawater in their geographic range is colder than that, reaching a frigid temperature of 1.9 degrees C. The cod are no warmer, but they swim along fineunless they are brought into contact with ice. Researchers studying the phenomenon in the fjords of northern Canada in the 1950s placed the fish on ice and watched: ice crystals surged across the cods skin, rapidly killing the fish and creating a frozen monument to metastable precarity.Whereas flash frozen cod are a classical phenomenon, false vacuum decay requires quantum tunneling, in which a highly improbable fluctuation takes the universe to a different state. How improbable is that fluctuation? If the universe is in fact metastable, recent calculations of vacuum decay have put its lifetime at about 10790 years, a number so large that you could wait another 13.8 billion years for the arrival of a better analogy, and cosmic annihilation would still be 10790 years away.Supposing you are fortunate enough to be around for a false vacuum decay, physicists have deduced that there is additional encouraging news. As a consequence of this rapid expansion, if a bubble were expanding toward us at this moment, we would have essentially no warning of its approach until its arrival, wrote Sidney Coleman, a theorist then at Harvard University, in a 1977 paper.Lacking a universe in a bottle to observe, physicists have learned to blow bubbles in a variety of media. A quantum annealer is slow and not very useful for computing, Vodeb says, but its thousands of qubits are ideal for such a simulation because theyre very controllable, allowing bubble formation to be easily initiated and observed.Last year Alessandro Zenesini and his colleagues at the University of Trento in Italy reported their observations of a bubble in a collection of about a million sodium atoms that were the size of a poppy seed and cooled to nearly absolute zero. In that case, the bubble consisted of clumps of thousands of atoms that flipped their orientation to emulate the shift from a false vacuum to a true one.Although such atomic clumps are closer to the conventional image of a bubble than the annealers qubits in the new study, they are still only a crude toy model of the universenotably, they lack any meaningful inclusion of gravity. We cannot say anything about the real universe based on the 2024 experiment in Italy, says Alessio Recati, a theorist at the University of Trento and a member of the group that conducted that earlier study.That, of course, raises a broader and somewhat important, albeit nonurgent, question: Is the cosmos actually metastable, distantly destined for extinction by cosmic bubbles? Could be, Zenesini says breezily. Who knows?