The results were 18 standard deviations away from what you would expect based on Bell’s theorem, which is a strong indication that superposition of temporal order is a fundamental feature of quantum mechanics.
But the experiment is stuck where it was a few decades ago: There are too many flaws. For example, many photons are lost during the experiment (about 1 percent of the photons sent in come out the other side to be measured). It is technically possible that the loss was preferentially occurring among a subset of photons that would restore correlations consistent with otherwise hidden variables.
The team has not isolated the hardware to a sufficient distance to remove sub-light-speed effects, and there are also some potential oddities typical of uncertain causal-order experiments. But this work points toward experiments that could close these loopholes, and we already have a history of closing the door on them.
Normally, when something weird like this is covered, we’re left with the ability to just see how weird our world actually is compared to our expectations. But this is one of those cases where many of the practical applications of understanding physics are already known.
“The [device used in this work] “It may also be interesting for applications as it has been shown that it can outperform appropriately 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,” the authors write.
In other words, being confused about time can actually be useful.
* I wouldn’t have even known this work had been done if I hadn’t seen its excellent summary on the American Physical Society news site.
prx quantum2026. DOI: 10.1103/5t2y-ddmt (About DOI).
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