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Storing Qubits In Nuclei
Posted by
kdawson
on Fri Oct 24, 2008 01:56 PM
from the now-you-see-it-now-you-still-see-it dept.
from the now-you-see-it-now-you-still-see-it dept.
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.
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bgC3 invented it! (Score:3, Funny)
I heard BGC3 has already patented this idea.
DRAM Deja Vu (Score:2)
Everything old is new again.
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Are you new here?
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Much to learn have you, young padewan.
DRAM, or dynamic RAM would hold it's contents for a short while, requiring "refresh" cycles. These would read the data out before it disappeared, and write it back. A similar mechanism would be necessary for this type of memory -- just like DRAM refresh, hence "deja vu": seen before.
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No, it isn't a reinvintion.
But, the need for refresh is what it shares in common with it, despite being due to decoherence instead of discharge.
In any case, it wasn't intended to be stupid, silly, or funny, and certainly not first: just a bit obscure, as in *whoosh, flies completely over head*.
As my girlfriend (Score:3, Funny)
An international team of scientists demonstrated that quantum information stored in a nucleus has a lifetime of about 1¾ seconds
Just as long as it takes me to c..
... compute 2 + 2
Nuceli, please! (Score:4, Informative)
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Nuceli, please!
No comment...
Let's go all the way (Score:2)
'in' takes the ablative, so let's go all the way and use the ablative plural, nucleis.
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Dude, I know. What a bunch of illiterate hicks.
Ah the memories.. (Score:3, Funny)
It wasn't so much that we thought "souvlaki" was a latin plural when the dish was clearly of Greek origin that bothered the restaurant owner so much as our constant bickering whether the singlar was "souvlakum" or "souvlakus".
(with apologies to Wayne and Shuster)
Kinda matches my attention span :-) (Score:2)
However, this isn't the first time short term memory has been used in computing. I can remember (pardon the pun) memory which had to be refreshed, so I'd imagine using that concept would fix the "short" timespan.
However, that's not the only important number. What about latency?
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> However, this isn't the first time short term memory has been used in computing.
No. There were mercury delay lines, for example.
> I can remember (pardon the pun) memory which had to be refreshed...
It's called DRAM (Dynamic Random Access Memory). It's the usual kind.
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I must admit I wonder just how much energy is lost in refresh operations. The problem is that nothing static is fast enough to keep up (AFAIK, it's been a while since I entertained myself with computing hardware).
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Did you mean nonvolatile instead of static? Static RAM can be significantly faster then dynamic RAM. I expect that NOR Flash could be as fast as dynamic RAM but the demand just is not there when in speed critical applications you can just copy from slow Flash into faster DRAM and lower the system cost.
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Not this kind of memory (Score:2)
I bet that refreshing a qbit will face all kinds of problems... More specificaly, the uncertainty principle forbids refreshing qbits, unless you want them to behave like clasical bits.
A computer based on this would have to make the hole quantum calculation on 1 3/4 seconds, all the way into a classical result. That would be enough to break RSA if there was a big enough computer, but I guess that isn't enough for everybody. Also, I don't know if it is possible to couple several nuclei and create a computer o
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More specificaly, the uncertainty principle forbids refreshing qbits, unless you want them to behave like clasical bits.
Well, I think that's the point. Just really small ones, so we can get a higher data density...
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the uncertainty principle forbids refreshing qbits
Only if you measure them. You can do quantum error correction using quantum computing itself (see this paper for example [citebase.org]).
A computer based on this would have to make the hole quantum calculation on 1 3/4 seconds
Since the coherence time is long (over a millisecond), quantum error correction can allow for almost any calculation. [eetimes.eu]
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There is another comment down there also pointing quantum error correction, if you reread my post you'll see that I talk about it. It isn't obvious (at least for me) that one can apply quantum error correction on that system, by the same reason that it isn't obvious that one can create a quantum computer from it.
I guess that if the researches tought that it was obvious how to apply such error corrections, they'd have cited that, so I assume nobody knows how to do that yet. Note that I pointed that somebody
How is this new? (Score:5, Interesting)
1.75 Seconds.... (Score:3, Informative)
Throw some DRAM-style refreshing in, and it could be viable at even that lifespan.
Bogus claim of "miniaturization" (Score:3, Insightful)
This could be the "ultimate miniaturization of computer memory", if not for the fact that each nucleus is wrapped in 15 electrons and about a trillion times its own volume of empty space. Unless, of course, they've found a way to contain degenerate matter and selectively polarize individual nuclei therein -- and I'm thinking compressing matter to degeneracy would tend to shorten those T1 times pretty substantially.
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But... (Score:3, Funny)
1¾ seconds should be enough for anyone!
Re:But... (Score:5, Funny)
Parent
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Me too! ;)
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Don't you mean,
Spelling and Grammer error have been added too this post for you enjoyment
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Anyway, go fuck yourself, we don't need users like you clogging up the support channels for people with actual need.
Don't worry, he only ties them up for 1¾ seconds.
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So their quantum computer already runs Windows? Whoa.
Re:So what (Score:5, Insightful)
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.
Parent
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Silicon for electronics has additional requirements. It isn't simply that it has to be ultra-pure for the element, but it also needs to be ultra-pure for the specific isotope. Further, there have to be minimal flaws in the crystalline structure across the entire wafer for any reason whatsoever. That gets complicated when you consider that modern chip making uses all kinds of techniques for doping, stressing and god-knows-what-elsing to improve performance, though there are other factors. If pharmaceuticals
Last time I looked chips WERE "painstakingly ..." (Score:3, Informative)
Last time I looked, single-crystal silicon technology (what's used in chips except for things like amorphous-silicon memory) consists
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A defect in the crystal structure results in the failure of every component that the defect is present in.
Every component, or one out of one. That's something like 100.00001863%
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Wow, you're still using a Pentium? I feel sorry for you.
In this context (Score:2)
Every component, or one out of one.
In this context a component is a circuit element on the chip (i.e. a transistor or the like) while the chip is an "assembly", not a "component".
Of course most chips don't have redundancy and fail if any of the (millions of) components on them are defective.
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> A defect in the crystal structure results in the failure of every component that the defect is present in.
That's not entirely true. The last time I checked, which has admittedly been some time, the defect rate was usually on the order of a part per billion or so. Excellent, certainly, but far from perfect considering that still means billions of billions of ... defects in each wafer. The key is that small, isolated defects are tolerable, so you only need to junk parts with high concentrations or an
Isotopically pure (Score:2)
I think that remark about high purity silicon is by the editor kdawson, not the submitter bednarz. I don't know where he came up with "painstakingly grown crystal of extremely high purity" - it's not in the NSF press release. But searching in Nature reveals the phrase "P-31 donors in isotopically pure Si-28 crystal" in the abstract. So maybe the isotopic (number of neutrons) purity of their material is above and beyond the chemical (number of protons) purity of standard microelectronic silicon.
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That sounds right. According to Wikipedia, the natural abundance of Si28 is 92%.
Googling got me an interesting paper:
http://www.crystalresearch.com/crt/ab35/1023_a.pdf [crystalresearch.com]
Not really related, but pretty pictures of silicon:
http://www.periodictable.com/Elements/014/index.html [periodictable.com]
Re:Storing both 0 and 1 simultaneously (Score:5, Funny)
Parent
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This is what I think happened.
A lab assistant pinned a periodic table chart at the end of the hallway.
Then one of the main researchers got to throw a dart at it blindfolded and it came up as Phosphorus.
"Looks like this time around we'll be using Phosphorus."
"Ok your turn...Ahhh Silica!
Let's get down to the beach, get some sand and shove some K into it and zap it with high voltage and see what it does!"
Seriously! Phosphorus is not the easiest thing to work with. Why that?
Re:Storing both 0 and 1 simultaneously (Score:4, Informative)
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.)
Parent
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Information? What information? There is no fucking information. It's both 1 and 0 from beginning to end, for crying out loud.
The information is not stored as the state of the particle but as the entanglement of the states of the set of particles. The state of a set of N entangled qbits encodes 2^N separate possible sets of states and thus 2^N bits of information, while one operation on the set can perform 2^N operations in parallel, one on each of the possible combinations of states.
Now there are a limited
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Quantum plural which is plural and singular at the same time?
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A quantum computer is cleverly built to operate in both the "crashed" and "running" states simultaneously. Since the "running" state is the only one that responds to the user's actions, users never have to interact with the "crashed" state. This makes Windows run much better.
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I barely understand it myself. A decent explanation by someone who gets it and can communicate in human language would be good :D
But from what I can gather... they do everything that standard binary computers do, but other things as well. Instead of just working on binary bits (which can be 1 or 0), they operate on qubits (which can be 1 or 0, in one dimension, but also have a quantum spin, adding another dimension). So essentially, they work with complex (2-dimensional) numbers as their basic level of c
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If noah was already building stuff with qubits, he was getting a lot more help from god than we all thought.
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Given that nuclear power comes from splitting atoms, I think you'd have to be combining atoms to "make" a nuclear battery. You'd be putting in as much energy as the later nuclear fission would give out (including what's lost as heat or light or whatever you don't use), plus some in manufacturing. We're probably not close to exhausting our resources of uranium etc., and fusion might eventually arrive before that happens, so it'd all be a bit pointless at this stage I guess. Definitely worth thinking about
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Fission and fusion can both be either endothermic or exothermic, depending on what you're working with. If you're working with atoms lighter than Iron, you get energy from fusion, and fission requires providing energy. If you're working with atoms heavier than Iron, you get energy from fission, and fusion requires providing energy. If you're working with Iron, you have to provide energy for both.