Tuesday, February 10, 2009

Quantum Teleportation Discovered, Er sort of...

Great news announced on LiveScience...

Teleportation Milestone Achieved

They just seem to have forgotten a few things. As far as I know, teleportation would actually require transmission of sufficient information needed to recreate and object in all ways that matter. If the object is a block of lead, you expect a similarly constructed block of lead. If the object is a single bit of information, I expect that exact same bit of information to arrive on the other end.
"But because ion A's state is irreversibly tied to ion B's, the measurement also forces B into the complementary state. Depending on which state ion A is found in, the researchers now know precisely what kind of microwave pulse to apply to ion B in order to recover the exact information that had been written to ion A by the original microwave burst. Doing so results in the accurate teleportation of the information."
By my reading, this section basically says, they look at the data, and determine based on the results what needs to happen on the other side. They then use this information on the other side. That implies that the data cannot be "transmitted or teleported" to the other side without having some other data sent as well. I could do this as well. I will give you an on bit on a piece of paper. Then, I will call you later and tell you if you should flip that bit or not. I look at my piece of paper, and then have you flip or not flip to match. If this could happen without outside information being passed, it would be astounding. Then our two pieces of paper would be linked. With the outside information, it seems a bit less of an advancement.
"What distinguishes this outcome as teleportation, rather than any other form of communication, is that no information pertaining to the original memory actually passes between ion A and ion B. Instead, the information disappears when ion A is measured and reappears when the microwave pulse is applied to ion B."
I am not sure if this is true. Based on the description, I could recreate a lot of the "value" of the experiment with a pen and a lighter. I read the value of A and store the instructions of whether or not to write on B. I then burn A. Now, I transfer those instructions to the other side, and follow them. Now B, either has a mark or not. Now granted, Quantum states are not the same as actual bits, since they support superpositions. Maybe that is the important difference. They also don't mention the complexity of the laser information that needs to be passed. Back to the article:
""One particularly attractive aspect of our method is that it combines the unique advantages of both photons and atoms," says Monroe. "Photons are ideal for transferring information fast over long distances, whereas atoms offer a valuable medium for long-lived quantum memory ... Also, the teleportation of quantum information in this way could form the basis of a new type of quantum internet that could outperform any conventional type of classical network for certain tasks.""
I am not sure how this system could "outperform any conventional type of classical network". What is a conventional type of classical network? Anyways, how can it outperform a conventional network unless it somehow gets around the fact that data must be transmitted between the two sites of entangled ions? If you need to send data across the wire to "retrieve" the information on the other side, unless that data is very small compared to the payload, it should not be able to outperform much of anything. When you need to take many tries to entangle ions before you can use them, and then end up with a 90% success rate, possibly without the ability to verify the result, it seems like it might not be that much of an advance.

One thing I liked about this paper was the way it described a very simple process for entangling similar ions from a distance. That, if it really works, is very cool and would help extend work in the quantum field.

I love the topic, I love the research, but I am looking for more.


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