A Quantum Memory Storage Prototype

eldavojohn writes "An Australian National University project has completed a proof-of-concept storage unit that relies on bringing light to a standstill inside a crystal and then releasing it later for a read-once storage device. There are a few complexities to work out, such as the -270 degrees Celsius requirement to stop the light. And there is an interesting side effect noted by the team lead: 'We could entangle the quantum state of two memories, that is, two crystals. According to quantum mechanics, reading out one memory will instantly alter what is stored in the other, no matter how large the distance between them. According to relativity, the way time passes for one memory is affected by how it moves. With a good quantum memory, an experiment to measure how these fundamental effects interact could be as simple as putting one crystal in the back of my car and going for a drive.' Hopefully this will lead to a better understanding and simple testing of quantum entanglement."

Re:Quantum communication?

[BlueKitties]

Spin of entangled particles only has a probability of collapsing into a specific state, i.e. information cannot be transfered.

Re:Quantum communication?

[Burnhard]

It does? It's pretty hard to get your head around. Using Bell's Theorem, it's possible to say that a unified theory cannot both be local and deterministic. That means you have to throw out one or the other. It also discounts hidden variables as an explanation for non-local effects (I think). So I suppose there's a good reason it's called "spooky"!

Re:Quantum communication?

[mea37]

I've read descriptions of the experiment that is supposed to rule out "hidden variables". It is statistical in nature, and I didn't (probably still don't) have a good enough grounding in the theory to really understand it (as physics isn't actually my field). So I can only say that all the credible texts on the subject claim that hidden variables could not account for what is observed.

It's called "spooky" because that was a term Einstein used to describe his initial dissatisfaction with the theory.

Re:So, no storage, but instant transmission?

[Anonymous Coward]

Also extremely heavy due to the liquid nitrogen cooling requirement, and point-to-point use only. Makes it more of a big walkie talkie than a cell phone.

-270 C... that's 3 above absolute 0. LN2 isn't going to cut it... the only cryogenic gas that's going to work is liquid Helium.

Re:Quantum Entanglement does not "transfer" anythi

[Interoperable]

That's incorrect. Remote state preparation absolutely does change the state of a distant particle. For example, consider the case that you have correlated particles such that they will both be measured in the same same state. Each particle is in a superposition of state 1 and state 0 but if one is measured to be a 1 then it prepares the other in state 1 and vice versa. Both particles could be in either state until one is measured, at that point the state of the other is prepared in the state of it's partner. No information is transmitted; however, because the state of the first particle is random anyway.

Read up on Bell's Inequality or the EPR paradox for an explanation of the fact that the state is truly random until it is measured and hence the entangled particle is remotely prepared.