The inferior limit doesn't mean the speed can't be infinite

Mar 7, 2013 20:11 GMT  ·  By

Quantum entanglement describes the link between two particles that are not physically close or in any form of contact, i.e. there's no information exchange, as far as modern physics is concerned, between the two particles.

Yet, these two particles are intrinsically linked, a property of one is mirrored in the other. Experimentally, scientists measure a property of one of the particles first.

This being quantum mechanics, they have no way of guessing what they'll see before the measurement. But once they have determined the state of the property, for example the spin of a particle, they'll be able to predict the spin of the linked particle as well.

True enough, when the other particle, which may be kilometers away and, in theory, half the universe away, is measured, the expected result is found every time.

Since quantum states, until measured, are considered undetermined, i.e. all states exist at the same time with different probability, only when one particle is measured is the state of the other determined.

One question, among many, that has plagued physicists about this is how fast this change happens, how long after the first measurement is taken that the state of the second particle becomes fixed.

This may as well be immediate, in fact that's the popular belief. That's the idea behind quantum teleportation as well.

Some Chinese scientists are determined to find out though. The same team that currently holds the record for quantum teleportation distance was able to determine experimentally that the "speed" of the entanglement has to be at least 10,000 times faster than the speed of light.

That's not the same as putting a number on it, but the experiment showed that if this speed is indeed finite, it is faster than light by at least four orders of magnitude. The results don't exclude the possibility that the speed is infinite.