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Storing Qubits In Nuclei
bednarz writes "Scientists have demonstrated what is being called the 'ultimate miniaturization of computer memory,' storing data for nearly two seconds in the nucleus of an atom of phosphorus. The hybrid quantum memory technique is a key step in the development of quantum computers, according to the National Science Foundation. An international team of scientists demonstrated that quantum information stored in a nucleus has a lifetime of about 1¾ seconds. 'This is significant because before this technique was developed, the longest researchers could preserve quantum information in silicon was a few tens of milliseconds. Other researchers studying quantum computing recently calculated that if a quantum system could store information for at least one second, error correction techniques could then protect that data for an indefinite period of time.'" Here's the NSF press release with pictures of the apparatus. They claim that this technique is promising because it "uses silicon technology" seems a bit of a stretch — the silicon the researchers employed was a painstakingly grown crystal of extremely high purity.
I heard BGC3 has already patented this idea.
The plural of nucleus is nuclei, please!
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Not only that, but it's not like the silicon used in today's chips is low grade crap. The purity standards for electronic grade silicon are pretty insane considered to the standards of most things we think of as "pure", including pharmaceuticals. (Seven to eight 9's purity is not uncommon). And yet its produced in great volumes relatively cheaply.
It's a front. The researchers all ganged up and wrote a bunch of nonsensical papers, then they used the grant money for blackjack and hookers.
I haven't had time to read the nature article quite yet, but it would appear that magnetic moment coherence information is transfered from electrons, which decohere quickly, to nuclei, which decohere much more slowly. Magnetic moments on nuclei in the solid-state and in the absence of local motions can maintain coherences for minutes to hours -- this is not surprising. However, I can't tell from this summary how this is different from DNP, a well established method. Maybe because it was done in silicon?
Somehow you store a qbit which is both 0 and 1. Then you try to retrieve it. Problem is, as soon as you do so, it collapses to either 0 or 1. So how do you know that what you stored is what you got back?
You don't retrieve it in a way that causes the entanglement to collapse. You instead transfer the enganglement to another particle which then participates in the next step of the computation (or perform that computational step on the nucleus that has been acting as a storage medium).
The first one corresponds to a memory (with a destructive read - because you can't COPY entanglement, so the qbit itself DOES collapse when the information is transferred out).
The second one corresponds to a bit in a datapath register where the computation takes place in the register logic rather than in a nearby hunk of logic. (I.e. the old "accumulator" style of processor typical through the 1960s.)
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