The results were within 18 standard deviations of what would be expected according to Bell’s theorem, which is a strong indication that superposition of temporal order is a fundamental feature of quantum mechanics.
But the experiment continues where the entanglement was a few decades ago: there are many loopholes. For example, many photons are lost during the experiment (about 1 percent of those sent out the other side to be measured). It remains technically possible that the losses occurred preferentially among a subset of photons that would otherwise restore correlations that are compatible with hidden variables.
The team also hasn’t separated the hardware at sufficient distances to rule out sublight velocity influences, and there are also some potential oddities specific to experiments of undefined causal order. But the work points the way to experiments that could close these loopholes, and we already have a history of slamming the door on them.
Normally, when we cover something strange like this, all we are left with is the ability to gape at how strange our world is compared to our expectations. But this is one of those cases where it is already known that understanding physics has many practical applications.
“The (device used in this work) may also be interesting for applications, as it has been shown to outperform causally ordered processes in a wide variety of tasks such as channel discrimination, promise problems, communication complexity, noise mitigation, various thermodynamic applications, quantum metrology, quantum key distribution, entanglement generation and distillation, among others,” the authors write.
In other words, getting confused about the time could be helpful.
*I wouldn’t even know this work was done if I hadn’t seen a excellent summary of it on the American Physical Society news site.
quantum PRX2026. DOI: 10.1103/5t2y-ddmt (About DOIs).
