A team of Chinese physicists have clocked the speed of spooky action at a distance — the seemingly instantaneous interaction between entangled quantum particles — at more than four orders of magnitude faster than light. Their equipment and methodology doesn’t allow for an exact speed, but four orders of magnitude puts the figure at around 3 trillion meters per second.
Spooky action at a distance was a term coined by Einstein to describe how entangled quantum particles seem to interact with each other instantaneously, over any distance, breaking the speed of light and thus relativity. As of our current understanding of quantum mechanics, though, it is impossible to send data using quantum entanglement, preserving the theory of relativity. A lot of work is being done in this area, though, and some physicists believe that faster-than-light communication might be possible with some clever manipulation of entangled particles.
Now, thanks to these Chinese physicists — the same ones who broke the quantum teleportation distance record last year — we know that spooky action at a distance has a lower bound of four orders of magnitude faster than light, or around 3 trillion meters per second. We say “at least,” because the physicists do not rule out that spooky action is actually instantaneous — but their testing equipment and methodology simply doesn’t allow them to get any more accurate.
To get this figure, the physicists entangled pairs of photons at a base station, and then transmitted half of each pair to two receiving sites. The receiving sites were 15.3 kilometers (9.5mi) apart, and aligned east-west so as to minimize the interference from the Earth’s rotation (which is significant, when measuring speed on this scale). One half of the pair was then observed, and the time for the other half to assume the same state is measured. This process was repeated continuously for 12 hours to generate enough data to accurately divine the speed of spooky action.
According to the physicists, other research groups have tried to measure the speed of spooky action before, but they’ve all had locality loopholes — flaws in the methodology that undermine the quantum nonlocality that the experiment requires. This time, the physicists claim, all the loopholes have been closed, and that their measurement of at least 3 trillion meters per second is accurate.
Where do we go from here? Good question. In recent months we’ve seen a group of international scientists teleport entangled photons over 143km (89mi), the first everteleportation between macroscopic objects, and the first fiber optic network that can carry conventional data and quantum data. We’re now at the point where a quantum internet — either using conventional fiber or satellites — is starting to become feasible. If it turns out that we actually can communicate data via quantum entanglement, we now know that it’ll be much faster than the speed of light.
At the very least, this is one of the first observations of the subluminal universe — a significant event for all scientists everywhere.