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Scientists Teleport Information Between Ions a Meter Apart
erickhill writes with word that scientists from the University of Maryland have successfully transferred information from one charged atom to another without having it cross the intervening space of about one meter. The academic paper is available in the journal Science, though it requires a subscription to see more than the abstract.
Scientists have previously teleported unmolested qubits between photons of light, and between photons and clouds of atoms. But researchers have long sought to teleport qubits between distant atoms. Light's high speed of travel makes photons good transporters of information, but for storing quantum information, atoms are a much better choice because they're easier to hold on to. 'This is a big deal,' comments Myungshik Kim, a quantum physicist at Queen's University Belfast in the United Kingdom. 'To store information as it is in quantum form, you have to have a teleportation scheme available between two stationary qubits. Then you can store them and manipulate them later on.'"
Are they positive?
Qubit molester insists entanglement was consensual, stay tuned for details at 11.
All sources regarding quantum entanglement/teleportation are quite adamant that you can't use it to actually send information instantaneously. Despite there being "spooky action at a distance", any discernible information had to be transfered when you separated the photons themselves at sub-light speeds. In this case it would be atoms, but I assume it still applies? The article lists applications as super-fast quantum computers (I guess any functional quantum computer could be considered fast at what it does) and quantum encryption (a real application I've heard applied to quantum teleportation, though the encrypted data itself still has to travel at c or less).
So, am I right, and this is basically the same ol' non-instant-communication but still quite cool kinda teleportation, only using atoms instead of photons? I'm just checking.
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My mother always knew what I had done without anyone telling her. Or whatever I was going to do before I took action. I hear other mothers have the same ability. Therefore, all mothers must exist in some state of constant quantum communication with each other.
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You mean a qubit molester?
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Ok, who voted for the beammeupscotty tag?
I can't think of a worse place to be beamed, than 'up scotty'.
Oh, if it were that easy. When you collapse the wave function my measuring one 'end' of your hypothetical particle-block, you: have NO WAY of influencing HOW it collapses, and thus cannot send any information to the other 'end'. You cannot determine what spin you will observe, only that the opposite spin will be observed on the other particle.
Is there any way to know that measurement has taken place at the other end and your local qubit has collapsed?
Crash course in quantum mechanics, perhaps this explains it: a binary quantum mechanical system is in a linear superposition of states A and B. That is, it is either 100% A, or 100% B, or anything in between; for example 70% A and 30% B.
Now if you measure, you would only get "pure" results, i.e. purely A or purely B. If the system was pure (i.e. 100% B) before the measurement, you get what it was. If the system was mixed (say, 70-30), and you had the chance to measure the system more than once, then you get A in 70% of the cases, or B in 30%. For example: make 1000 copies of the system, and measure each of them. Roughly 700 (give/take a few) would be A, roughly 300 would be B.
The biggest problem is that you don't have 1000 exact copies -- unlike with classical information, basic QM forbids cloning of a system. So you basically have one shot, and if you happen to measure B, you'll never know whether it was because of a 100% pure B state, or simply because you "got lucky".
I mean, I know the answer is you can't communicate instantly, I'm just figuring out why (mostly to help explain to people with roughly my same layman's understanding of physics why instant communication is impossible).
While the "quantum information" is being transfered instantaneously, the problem is that the quantum state is not transfered 1:1 onto the target. It is ... "twisted". Imagine that like x*A+y*B (-> teleport ->) y*A+x*B. Now you know that the numbers x and y mean the same in both systems -- you just don't know exactly how they would be twisted after the teleportation. There are 4 possibilities how they can be twisted, and all 4 are equally probable, there's nothing you can do to favor the one over the other.
However, after the teleportation, the guy at the source can tell how they have been twisted (because the teleportation act itself is a measurement, which's result tells him exactly what happened), but the guy at the target does not.
So at first, even if the guy at the target knows that the atom has been "teleported", he stil doesn't know which one of the 4 twisted flavors of the original atom he got. If he just takes a "wild guess" and tries to measure, he'll get a statistical result which reveals absolutely no information about the actual coefficients.
The target-guy needs the source-guy to tell him which of the 4 twists occured, or in short: needs an information transfer in order to be able to "untwist" his atom and have an exact copy.
Again, the important part is that if the target-guy does not "untwist" his atom, but instead decides to go away and measure it anyway, he'll have an overall chance of 50-50 (regardless of the original x and y) to measure either A or B, so there's no information whatsoever that he could gain, not even from repeating the experiment.
It's the "twist" that makes the twist with teleportation... :-)
Here's an illustration of the non-tranmission of information via entanglement.
Suppose we have a pair of 'magic coins'. Either coin can be flipped and come up either heads or tails, and the other coin will always come up the opposite.
Now, suppose 2 people meet in New York and agree that they will meet again in Oslo if Amy's coin comes up heads and Bill's coin comes up tails, or they will meet in Sidney if Bill's coin comes up heads and Amy's coin comes up tails. Then Amy goes to Peking and flips her coin. It comes up heads, so she meets Bill in Oslo.
The information, which city they will meet in, was AGREED ON BEFORE HAND, it wasn't 'transmitted' by the flip of the coins. The information was in Amy's head when she went to Peking, it traveled by a classical channel governed by relativistic limitations.
This can be seen explicitly if you assume that Amy and Bill DIDN'T agree on which face of the coins meant Oslo or Sidney. In that case when Bill and Amy flip their coins they DO know that their opposite number's coin came up the other way, but neither of them knows which city to go to! In other words, no information was conveyed between them BY the flip of the coins.
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