The M.P.Q. group put their prototype network through a series of tests—transferring a qubit from a single photon to a single atom and reversing the process to transfer information from an atom onto a photon. Combining those read/write operations, the physicists managed to transmit a qubit from one rubidium atom to another located in a separate laboratory 21 meters away, using a messenger photon as the carrier between nodes. (The actual length of optical fiber connecting the two nodes is 60 meters, because it snakes along an indirect route.)

A significant number of the photons get lost along the way, limiting the efficiency of the process. But in principle, optical fibers could connect nodes at greater distances. "We're absolutely not limited to these 21 meters," Ritter says. "This 21 meters is just the distance that we happened to have between the two labs."

The researchers also demonstrated that their photonic link can be used to entangle the two distant atoms. Quantum entanglement is a phenomenon by which two particles share correlated properties—in other words, the quantum state of one particle depends on the state of its entangled partner. Manipulating one of the particles, then, affects the other particle's state, even if it is located in another laboratory. Researchers hope that entanglement can be harnessed to circumvent the photon losses that come from passage through optical fibers. In a proposed application called a quantum repeater, a series of nodes, linked by entanglement, would extend the quantum connection down the line without depending on any one photon as the carrier.

Ritter acknowledges that the new work is simply a prototype, and one for which numerous improvements are possible. For instance, the transfer of a quantum state between labs succeeded only 0.2 percent of the time, owing to various inefficiencies and technical limitations. "Everything is at the edge of what can be done," he says. "All these characteristics are good enough to do what we've done, but there are clear strategies to pursue to make them even better."

11 Comments

1. 1. edelbrp 08:07 PM 4/11/12

   It should be important to note that there is an important distinction between 'quantum' information and 'classical'. Classical is what we would generally call useful in terms of sending useful messages and data. 'Quantum information' is only useful to other quantum systems and has to be coupled with classical information transfer systems to generally be of any use to us.
   
   Also, there have been off the shelf quantum-based data systems on the market for years now. (You can google for them yourself.) I'm not calling this article uninteresting, just a little ambiguous as to what is actually new here and what it can be used for in practical terms.

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2. 2. sidelight 09:13 PM 4/11/12

   Begging the question, isn't the whole Universe a quantum information system ?
   It will turn out easier that they are making it.
   

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3. 3. egoburnswell 07:05 AM 4/12/12

   I would like to suggest an alternate title for this article:
   "Mr. Photon--come here--I want to see you".

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4. 4. TomGrinley 08:27 AM 4/12/12

   ...and the first message was "Heisenberg, come quickly, your cat needs you"

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5. 5. ggodwin 12:06 AM 4/13/12

   I'm not sure what Schrodinger would think of that

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6. 6. brublr 08:27 PM 4/13/12

   "Consciousness is a singular for which there is no plural." - Erwin Shrodinger

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7. 7. nirmalgopa 07:58 PM 4/14/12

   What do you mean by a photon ? If so, what is the mass of it ? In the equation of Planck energy E = hγ ,we know, h = Planck Constant. Is h a photon energy ? If so, this is totally incorrect. This h is a bunch of photon energy. I explain it in my book "Complete Unified Theory" (page- 424, 1998). Photon is a ultimate particle. All matter is made up of photons. In what way the particles, matter, thus the universe created, I explained in my book. There is no variation of results between calculated results and experimental results. You can get almost all type of answer from this book.
   Nirmalendu Das.
   Dated: 15-04-2012.

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8. 8. MutantBuzzard 04:55 PM 4/15/12

   WOW who'd a thunk somthing so complcated could b so simpel?

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9. 9. MutantBuzzard 04:59 PM 4/15/12

   so what r photons made of?

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10. 10. MazarSc 03:01 PM 4/18/12

    I think they can't generalize it to say Network, while they still R/W to only one bit of information.

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11. 11. bucketofsquid in reply to MazarSc 01:52 PM 4/25/12

    It is a network in the same way as a very primitive 2 celled organism is a network. Not a network as we currently know it but calling it a network is grammatically correct.

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