Black Holes May Collapse Quantum States as Fast as Physics Allows

Insider Brief

• A new theoretical study suggests black holes destroy nearby quantum superpositions with perfect efficiency, linking gravitational environments to fundamental limits of quantum information.
• Researchers showed that information gained by an observer inside a black hole would precisely match the loss of coherence in a quantum object outside it, implying black holes operate at the edge of quantum limits.
• The findings, presented at the American Physical Society’s Global Physics Summit, suggest space-time geometry could emerge from information flow, with implications for quantum gravity and foundational physics.

A new theoretical study suggests black holes may not only trap information, but destroy fragile quantum states near their boundaries with unmatched efficiency, a finding that could reshape how physicists think about the fabric of space and time.

Physicist Daine Danielson of the University of Chicago presented the work at the American Physical Society’s Global Physics Summit in March. His team showed, through a mathematical model, that an observer hiding inside a black hole could in theory extract information about a quantum object outside it, and in doing so, would trigger a detectable effect known as decoherence. That effect — the collapse of a quantum system into a single state — is familiar to quantum computing researchers who struggle to preserve the delicate superpositions required for quantum processing.

The researchers proved that the amount of information the hidden observer could gain would exactly match the degree of decoherence experienced by the quantum object outside. In other words, the outside observers would see their systems fall out of superposition precisely to the extent that the eavesdroppers inside the black hole learned something about it.

The Universe’s Most Extreme Barrier

This relationship between information gain and decoherence is well-known in quantum information theory. What’s new is where Danielson and his collaborators applied it: across one of the most extreme barriers in the universe — the event horizon of a black hole.

Danielson told New Scientist that he and his team set up a thought experiment involving two people, Alice and Bob, separated by a black hole. Alice prepares a quantum object — such as a qubit — in superposition. Bob, seeking to gather information without being detected, hides inside the black hole.

“[Bob] doesn’t want to get caught, but he’s clever and he realises that he could hide inside of a black hole,” Danielson told New Scientist.

While it’s widely accepted that information cannot escape from inside a black hole, the team asked whether Bob’s interference could still influence Alice’s quantum object in a measurable way. The answer, according to their math, is yes.

In quantum physics, a superposition means a system exists in multiple probabilistic possible states at once. This is the foundation for quantum computing, where a qubit can represent both 0 and 1 at — for all intents and purposes — the same time. But these states are fragile. Even a minor interaction with the environment can “collapse” the state, a process called decoherence. Physicists have long known that decoherence and information leakage are two sides of the same coin: if someone gains information about a quantum system, its superposition is lost.

Danielson’s team took this principle and applied it to the space around black holes. They found that if Bob’s actions from inside the black hole caused decoherence outside, then the amount of decoherence Alice sees must match the maximum amount of information Bob could theoretically extract. Otherwise, Alice would be able to infer something about the black hole’s interior, violating the principle that what happens inside a black hole’s event horizon must remain hidden.

Perfect Efficiency

This leads to a striking implication: black holes must decohere quantum states near them with perfect efficiency.

“It implies that every black hole has to decohere superpositions in its vicinity,” the researchers wrote.

Alex Lupsasca, a physicist at Vanderbilt University not involved in the study, told New Scientist the work reveals, “yet another way in which they are the best at everything they do: black holes can destroy quantum superpositions with their strong gravity, and they do so in the fastest possible way”.

For researchers in quantum computing and quantum foundations, the work draws a compelling connection between gravitational environments and the laws that govern information flow. The study suggests that black holes operate at the edge of quantum limits — not just in how they trap matter, but in how they erase quantum coherence.

The Nature of Space and Time

The team’s work also raises broader questions about the nature of space and time itself. In an extension of their thought experiment, the researchers proposed replacing the black hole with a spherical shell made of ordinary matter. In that case, the decoherence behavior changes, depending on the shell’s structure. This opens the door to the idea that space-time geometry may not be fundamental, but a consequence of how information flows between quantum systems.

“There’s a hope that this might give us some insight into the way in which space and time themselves could emerge from information theoretic principles,” Danielson told New Scientist.

That line of thinking echoes ideas from holography, quantum gravity and quantum error correction — fields where space, time and gravity are believed to emerge from more basic laws of quantum entanglement and information sharing.

“Since black holes play such an important role in the major open questions about quantum gravity, it is important to have a clear understanding of how their quantum effects differ from those of ordinary bodies,” Sam Gralla, a physicist at the University of Arizona, told New Scientist. He added that the researchers’ calculations could be used as a benchmark to test candidate theories for quantum gravity.

The work does not propose an experiment or observable signal; black holes remain far from reach of practical testing. But the mathematical consistency of the results offers physicists new ground on which to test theoretical models of quantum gravity.

The team also concluded that this black-hole-induced decoherence likely requires the presence of ultra-low-energy particles, which could be present in the space surrounding black holes. These particles, if better understood, might help connect theoretical models with real-world physics.

The though experiment may put those in quantum tech industry in an unusual spot. In quantum technology, decoherence is typically something to minimize. But in this context, it’s not just a nuisance — it’s a clue to how gravity and quantum mechanics might be speaking the same language. And black holes, once feared for hiding information, may be showing us how the universe processes it.