The photon that wasn't teleported

Featured image credit: skeeze/pixabay.
Featured image credit: skeeze/pixabay.

Last month, Chinese researchers announced that they had performed two amazing feats. First, they had performed an experiment recreating the spooky phenomenon called quantum entanglement. To borrow a clunky but sufficient explanation from the MIT Tech Review article tweeted above:

[Entanglement] occurs when two quantum objects, such as photons, form at the same instant and point in space and so share the same existence. In technical terms, they are described by the same wave function. The curious thing about entanglement is that this shared existence continues even when the photons are separated by vast distances. So a measurement on one immediately influences the state of the other, regardless of the distance between them.

While the phenomenon has been demonstrated in (not-large) labs around the world, the Chinese launched a satellite adept at receiving and measuring the properties of photons, and then created pairs of entangled particles from the ground and fired one half of them to the satellite. When they measured the properties of one of these photons, the other photon also changed accordingly. Effectively, they’d realised entanglement over more than 500 km.

The second feat they performed was to generate some information – and not just bland photons – and instantaneously access that information through the use of entangled photons across large distances. This feat made for the first proper precursor to an information transfer system protected by quantum cryptography, which isn’t susceptible to conventional means of hacking because there is no information flow, just instantaneous information access at the two endpoints of a channel.

Now, while both experiments were great, neither the Tech Review article nor BBC article got it completely right. Both their headlines speak of an object having been teleported; this is wrong. No objects were teleported but information was, and this is a crucial difference because the advent of quantum entanglement has not changed what it means to be teleported. In the continuing regular use of the word, teleportation requires the selfsame object to disappear, or disintegrate, at one point and reappear at another instantaneously. It is the travel of the object through a large distance in space but almost no distance in time. The Chinese photons did not do this. The information contained by them did.

Two afterthoughts:

  1. Would acknowledging this difference have made for a less “sexy” headline? E.g., Information teleported to Earth’s orbit. I don’t think so. I think it sounds just as cool because teleportation is always cool.
  2. If you’re thinking the headlines might just be admissible because you subscribe to the physicist John Wheeler’s idea that “everything is information”, you’re wrong. Relevant bit:

… as the physicist Rolf Landauer liked to say, all information is physical – that is, all information is embodied in physical things or processes – but that doesn’t mean that all things physical are reducible to information. The concept of information makes no sense in the absence of something to be informed – that is, a conscious observer capable of choice, or free will.

Featured image credit: skeeze/pixabay.