Storing Qubits In Nuclei 90
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.
Nuceli, please! (Score:4, Informative)
Re:Kinda matches my attention span :-) (Score:3, Informative)
> 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.
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 EXPLICITLY of "painstakingly grown crystal of extremely high purity".
- A defect in the crystal structure results in the failure of every component that the defect is present in.
- Carefully-controlled Minuscule fractions of impurity atoms selectively substituted for silicon atoms define the active regions. Unplanned impurities change the characteristics, resulting in components that don't behave according to design.
So existing silicon technology is exactly what is required. Bednarz's concerns are off the mark. The purity and crystalline nature of the component won't impose any extra costs, because it's what is already done.
Some OTHER requirement MIGHT make it costly. But that's a separate issue.)
Re:So what (Score:3, Informative)
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 can be improved in microgravity, where the smallest unit you care about is an entire complex molecule, a process that is sensitive to the displacement of single atoms is necessarily going to be much more sensitive to any issues full Earth gravity is going to throw into the mix. (I'm not saying that that's a real problem, only that if the oft-quoted case for pharmaceuticals is true, it must be hundreds if not thousands of times more so for wafer production.)
The way silicon wafer production tends to work is to assume a moderate rejection rate. Chip makers test the chips and if they fail QA may simply be re-stamped at a lower grade. The best-known example of this was the early production of the 486SX and the 487, which were just 486DXes in which either the main CPU or the coprocessor had failed in testing. Those from Britain may also be familiar with Sir Clive Sinclair buying rejected chips on the grounds that most rejects for industrial use were perfectly acceptable for home use, and the cost of replacing was still cheaper than buying the better quality chips.
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.)
1.75 Seconds.... (Score:3, Informative)
Throw some DRAM-style refreshing in, and it could be viable at even that lifespan.