In reality, empty space is never truly empty. Even a quantum field in its lowest energy state, the vacuum, has inevitable fluctuations arising from the Heisenberg uncertainty principle: certain pairs of properties cannot have precisely defined values at the same time. In real-world terms, this means that a quantum field should look like a static television, and much indirect evidence suggests this is the case. Now, however, physicists led by Yansheng Zhang of the University of Cambridge in the United Kingdom have made a breakthrough: They have directly imaged fluctuations in a laboratory-made quantum field. “The observation of such fluctuations in the sine-Gordon limit opens many possibilities for laboratory simulations of relativistic fields in regimes that are currently not theoretically tractable,” they write in a preprint posted on arXiv. frameborder=”0″ enable=”accelerometer; autoplay; writing on clipboard; encrypted media; gyroscope; picture in picture; web-share” referrerpolicy=”strict-origin-when-cross-origin” enablefullscreen> Vacuum fluctuations aren’t just a theoretical pun: they actually have real effects on the physical Universe. Excited atoms interacting with fluctuations in the vacuum can spontaneously decay to a lower state, emitting a photon in the process. Electrons in a hydrogen atom can have slightly different energy levels due to fluctuation interactions. Then there’s the Casimir effect. Yes Yes If you place two conducting plates close together in a vacuum, they experience a measurable force pulling them together due to the difference in quantum fluctuations between the plates compared to the outside of the plates. Heck, they even play a role in the theoretical Hawking radiation emitted at the boundary of a black hole. And in cosmology, small primordial quantum fluctuations are thought to have spread to enormous scales during cosmic inflation. matter, ultimately producing the cosmic network of galaxies and clusters we see today. Quantum field theory describes the Universe as permeated by fields, with particles emerging as excitations in those fields, each of which behaves like a quantum harmonic oscillator with even inevitable uncertainty. in its lowest energy state (Zhang et al., arXiv, 2026) Each mode behaves a bit like a quantum harmonic oscillator: the quantum mechanical version of a mass bouncing on a spring, and thanks to quantum uncertainty, even in its lowest possible energy state, that oscillator can never be perfectly still. But for something that has such profound effects on the physical Universe, quantum fluctuations are extremely difficult to observe directly. They do not present a clear target for scientists to target with a detector. Therefore, quantum fluctuations have measured their consequences, not the fluctuations themselves. This is where Bose-Einstein condensates come into the picture. A Bose-Einstein condensate (BEC) is a cloud of ultracold atoms, cooled to just a hair above absolute zero. So instead of trying to image the vacuum of empty space, Zhang and his team built a quantum field that they could observe: a two-dimensional BEC of potassium-39 atoms. The researchers used two different internal states of the potassium-39 atoms, which they coupled using radio waves. The researchers directly imaged the vacuum fluctuations in their lab-made quantum field as they evolved over time (Zhang et al., arXiv, 2026). of vacuum, the researchers exploited the properties of quantum oscillators with an amplification experiment. First, they primed the spin field near its ground state. The coupling between the two atomic states was designed to amplify the small fluctuations already present in the field. An oscillator sitting at zero energy would not respond to this change by suddenly starting to oscillate, but a quantum oscillator in its ground state is not perfectly still. These pre-existing fluctuations evolve into measurable oscillations, and this is what the researchers observed become really fun. They performed the same measurements without amplifying the fluctuations first, observing how the strength of the fluctuation changed with frequency exactly as expected for vacuum fluctuations, rather than thermal noise. researchers a laboratory model in which they can potentially observe how quantum fluctuations evolve into much larger, more complex phenomena. Related: Physicists simulated a black hole in the laboratory, and then it started to glow There are some situations in quantum theory where the mathematics becomes tremendously difficult. This new system means that, instead of sitting and solving horrendous equations, scientists could potentially build a controllable quantum system governed by analogous physics and observe what happens. system could help investigate situations such as false vacuum decay, a potentially Universe-destroying process; and the formation and decay of topological defects in quantum fields. “The fact that we can directly observe field fluctuations in the regime where quantum uncertainty dominates over thermal noise could offer a unique window into the microscopic mechanisms that govern these phenomena,” they write. This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we take pride in our process, we’re human. If you spot an error, please let us know.
