Scientists at the University of New Brunswick have used humanity's most precisely measured atom to test one of modern physics' most audacious ideas: that quantum entanglement and wormholes are, fundamentally, the same thing.
The ER = EPR conjecture, proposed in 2013 by physicists Juan Maldacena and Leonard Susskind, bridges two concepts that have seemed worlds apart. One comes from quantum mechanics—entanglement, the phenomenon where particles separated by vast distances remain mysteriously correlated. The other emerges from Einstein's general relativity: hypothetical tunnels through spacetime, or wormholes. The conjecture proposes that these two phenomena are different expressions of the same underlying reality. For nearly a decade, it has remained one of the most tantalizing open questions in physics.
Ph.D. student Irfan Javed and Professor Edward Wilson-Ewing decided to test it using an unlikely candidate: the humble hydrogen atom. "It may give some hints towards a theory of quantum gravity," Wilson-Ewing said of the conjecture. Their reasoning was elegant. The hydrogen atom—a single proton and electron bound by electromagnetic attraction—is the most precisely studied system in all of physics. Its hyperfine structure, the tiny energy shifts arising from magnetic interactions between the spins of the proton and electron, has been measured to 12 significant figures. This is the level of precision where even vanishingly small deviations from theory become detectable.
More crucially, the proton and electron in a hydrogen atom are intrinsically entangled, not prepared by outside experimenters but simply by virtue of being bound together. If the ER = EPR conjecture is correct, then every hydrogen atom becomes a probe of the link between entanglement and wormholes.
The researchers' hypothesis rested on a key insight: if a quantum wormhole really connects the entangled proton and electron, some of the electron's electric field should leak into that wormhole—but not the proton's. "The proton is not affected by the wormhole because it is much bigger, and effectively doesn't see the wormhole," Javed explained. Wilson-Ewing offered a fluid analogy: "Consider a fluid representing the electron's electric field. What happens if a drain is placed close to the source? Some of the fluid is lost into the drain. The wormhole here is like a drain that some of the electric field can leak into."
This leakage would weaken the electron's effective charge—an effect that, in a system as precisely measured as hydrogen, should be observable if it exists.
The study, published in Physical Review Letters, found no such effect. The researchers showed that under their assumptions, the ER = EPR conjecture would imply detectable alterations to hydrogen's hyperfine structure and the electron's effective charge. Yet these alterations have never been observed, placing strong constraints on the conjecture.
This doesn't disprove ER = EPR, but it does narrow the possibilities—requiring any valid version of the conjecture to avoid producing measurable changes in hydrogen's properties. The result illustrates how even the most abstract theoretical ideas in physics can be tested against the natural world, and how precision measurement remains one of science's most powerful tools for probing reality.