Ultracold rubidium atoms used to simulate Schwinger pair production in a lattice

Physicists at the University of Science and Technology of China and partner institutions have built a cold-atom quantum simulator that models the creation of particle-antiparticle pairs from the vacuum. The experiment, reported in Physical Review Letters, uses ultracold rubidium atoms in an optical lattice to stand in for particles and electric fields. It offers a controllable way to study a process that is extremely difficult to reach in a conventional laboratory.

The problem: a suppressed effect

Quantum electrodynamics predicts that a sufficiently strong electric field can turn some of its energy into a particle and its antimatter partner. Such a partner has the same mass and, for charged particles, the opposite charge. This process, known as the Schwinger effect, is strongly suppressed at the field strengths that can be produced in the laboratory, which is why direct observation has remained out of reach.

The researchers frame the effect as an example of false vacuum decay, in which a metastable state releases energy by changing into a lower-energy one. Zhen-Sheng Yuan, co-senior author of the study, said the team wanted a simple, tunable laboratory model in which the process could be simulated and its progress controlled.

How the simulation works

The team trapped ultracold rubidium atoms in a one-dimensional chain of optical traps formed by laser light. Every second trap held two atoms, and the traps between them were left empty. This pattern represents the false vacuum.

The researchers then adjusted the settings so that atoms could hop between neighbouring sites in a way that mimics pair creation. The background electric field was set through the tuning of the system. A quantum gas microscope imaged the atoms at successive times, allowing the evolution of the lattice to be followed directly.

What the measurements showed

The team varied both the mass of the simulated particles and the strength of the background field. Fewer pairs formed when the simulated particles were heavier, and also when the electric field became too dominant relative to the other interactions in the model.

The researchers also related pair production to the vacuum persistence amplitude. Its squared magnitude gives the probability that the initial vacuum survives. In some limits they saw long-lived oscillations. With the simulated particle mass set to zero, the oscillations resembled the collective excitations predicted by the Schwinger model, a simplified one-dimensional gauge theory widely used to study such physics.

Scope and next steps

The work is a simulation, not an observation of the Schwinger effect in electromagnetic fields. Its value lies in showing that a lattice of neutral atoms can reproduce key features of a gauge-theory process and that the parameters governing it can be tuned and imaged. The source does not report quantitative comparisons beyond the trends described above, and the system is limited to one dimension.

For researchers working on quantum simulation and lattice gauge theory, the platform adds an experimental route to dynamics that are hard to compute classically and impossible to see directly in nature. The team plans to study what happens when the simulated particles meet, collide and scatter. It also hopes to extend the set-up from a single chain to two dimensions and to other gauge theories, where phenomena such as string breaking could become accessible.

The paper, by Zi-Hang Zhu and colleagues, is titled "Probing False Vacuum Decay on a Cold-Atom Gauge-Theory Quantum Simulator" and is also available on arXiv.

Source: Ultracold atoms simulate hard-to-observe matter-antimatter pair production (Phys.org, 31 October 2026).

Image: AI-generated illustration.