Bizarre quantum bonds connect distinct moments in time, suggesting that quantum links — not space-time — constitute the fundamental structure of the universe.
In 2012, Jay Olson and Timothy Ralph, both physicists at the University of Queensland in Australia, laid out a procedure to encrypt data so that it can be decrypted only at a specific moment in the future. Their scheme exploits quantum entanglement, a phenomenon in which particles or points in a field, such as the electromagnetic field, shed their separate identities and assume a shared existence, their properties becoming correlated with one another’s. Normally physicists think of these correlations as spanning space, linking far-flung locations in a phenomenon that Albert Einstein famously described as “spooky action at a distance.” But a growing body of research is investigating how these correlations can span time as well. What happens now can be correlated with what happens later, in ways that elude a simple mechanistic explanation. In effect, you can have spooky action at a delay.
These correlations seriously mess with our intuitions about time and space. Not only can two events be correlated, linking the earlier one to the later one, but two events can become correlated such that it becomes impossible to say which is earlier and which is later. Each of these events is the cause of the other, as if each were the first to occur. (Even a single observer can encounter this causal ambiguity, so it’s distinct from the temporal reversals that can happen when two observers move at different velocities, as described in Einstein’s special theory of relativity.)
These temporal correlations are also challenging physicists’ assumptions about the nature of space-time. Whenever two events are correlated and it’s not a fluke, there are two explanations: One event causes the other, or some third factor causes both. A background assumption to this logic is that events occur in a given order, dictated by their locations in space and time. Since quantum correlations — certainly the spatial kind, possibly the temporal — are too strong to be explained using one of these two explanations, physicists are revisiting their assumptions. “We cannot really explain these correlations,” said Ämin Baumeler, a physicist at the University of Italian Switzerland in Lugano, Switzerland. “There’s no mechanism for how these correlations appear. So, they don’t really fit into our notion of space-time.”
Building on an idea by Lucien Hardy, a theoretical physicist at the Perimeter Institute, Brukner and his colleagues have studied how events might be related to one another without presupposing the existence of space-time. If the setup of one event depends on the outcome of another, you deduce that it occurs later; if the events are completely independent, they must occur far apart in space and time. Such an approach puts spatial and temporal correlations on an equal footing. And it also allows for correlations that are neither spatial nor temporal — meaning that the experiments don’t all fit together consistently and there’s no way to situate them within space and time. More.
See also: Why “space” is hard to understand Physicist Paul Davies: A quantum “vacuum frolic” could substitute for absolute space.
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See also: What great physicists have said about immateriality and consciousness
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