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Purdue Builds Quantum-Computing Semiconductor
Bfaber writes: "According to EET, Purdue has created the first examples of quantum computing in a semiconductor. The story can be read here. Read the article for further links that include an audio interview."
Try this one (http://www.eet.com/story/OEG20010924S0101)
Blah, blah. Lameness filter doesn't like short posts so I'll put a little padding here. Sorry to ramble, but you know how it is...
Be careful. People in masks cannot be trusted.
http://news.uns.purdue.edu/UNS/html4ever/010917.Ch ang.quantum.html
Tom.
Oh arse
If you havn't you should read a book by Simon Singh called the "Code Book" it essentially is a history of cryptography from beginning to end (e.g. quantum cryptogrophy)....
The effects of quantum cryptography is huge... Using a quantum computer would allow you to crack huge keys (everything from PGP, RSA, DES, TwoFISH, BlowFISH, etc.... anything you can think of) because of the essential basis of quantum physics...
Simply in laymen terms you can check muliple cases of a key (i.e. check 111111 and 111112) at the same time... Not just 2 keys but, how about 2 billion keys per second... This makes any key no matter how long easily crackable...
I promise you the NSA is up early this morning banging on doors at Purdue (hey the probably funded it anyway)....
Now don't fear... Even though it makes any code breakable it also inheriently creates an unbreakable code using the same theories...
So start writing all you stuff down and locking in a safe instead of encrypting it on your hard drive.... You data really isn't safe anymore...
If they manage to get quantum computing working soon, and working well, we can forget these planned anti-crypto laws. Most crypto algorithms would go useless.
With quantum computers, the only way to do crypto would be transferring huge XOR mask keys physically (or possibly with quantum encryption channels). Pretty hard.
It's easy to get confused about quantum computers, because the media hype doesn't take into account the fact that you need at least two degrees (comp sci and physics) to understand it properly... guess what, I don't have these! But I do have the first, and my girlfriend has the second. :-)
/ vo l4/spb3/
Quantum cryptography itself is not an algorithm as such, but a way of using the inherent uncertainty in the polarisation of photons to ensure completely private communication. There are some labs which claim to have such a scheme working, but it's a long way from becoming feasible on a large scale.
Basically, it works on the principle that observation changes the observed event. You can ensure a secure (non-eavesdropped) channel by makeing sure that every photon has arrived correctly. If an intruder has observed your message, then the message itself has changed (at the quantum level)! I'm really not sure how it all works either, but there is plenty of published work.
The other crypto-related quantum computing thing is Shor's algorithm. For a reasonably good explanation:
http://www.doc.ic.ac.uk/~nd/surprise_97/journal
In essence, factorisation of large numbers (which is an NP complete problem on conventional hardware) can be done really quickly. This threatens RSA, Diffie-Hellman etc (anything which relies on the non-factorability of products of large primes).
I expect there's a similar "quantum" attack on symmetric encryption schemes like IDEA and DES, which would just do very fast brute force searches on the key space.
Hope this clears up some misconceptions!
These sigs are more interesting tha
As for the article, itself, It looks like aninteresting development -- but I'm kinda disappointed that they're looking at a few years for the next substantive step.. At this rate, I may be retired by the time a 'real' quantum computer is produced.
Sometimes boldness is in fashion. Sometimes only the brave will be bold.
Maybe the Purdue group will be able to shield their quantum dots from decoherence better than previous research on such objects has done so far. But as far as I know there is no getting around this; the best anyone can do is compute everything and read out your results before decoherence sets in.
This is not such a big breakthrough, folks. Hold onto your hats. If they can show that they can do operations much more quickly than old methods of dealing with quantum dots, or they can keep decoherence at bay longer than anyone expected, that would be the big breakthrough.
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
Isn't a cup of really hot tea also a semiconductor?
Somebody please correct the problems here. I don't really know what I am saying and am bound to be wrong in places.
-j
What would a mass production chicken farm need with a quantum computing semiconductor?
Outdoor digital photography, mostly in New Engl
Researchers are indeed working on long distance quantum cryptography. See this economist article from June this year.
Basically, a team at Los Alamos in New Mexicio are hoping to send quantum photons accross 10 Km of dessert. If that works, it shouldn't be much more difficult to send secure data to and from a satellite in orbit (since most of the 'thick air' is below 10Km, if you can get it that far, the rest of the way is fairly easy)
All this was discussed in an old slashdot thread
-- We don't understand software, and sometimes we don't understand hardware, but we can *see* the blinking lights
ResearchIndex should be in everybody's bookmarks.
h tml
In the previous post, I wasn't quite clear (shoot me, it's 5am and I've been up all night): there are a couple of different methods that I was pulling information from. In the penultimate paragraph, the final sentence was an aside referring to a method of using entanglement to transfer the keys. The rest of the post was referring to a method using polarisations and Heisenburg. Here are the two links to the papers.
First, for the transfer by polarisations. If you are at Cal, then go ask Vazirani, it looks like he has coauthored with them: http://citeseer.nj.nec.com/bennett92experimental.
Then on the use of entanglement (they do not have the actual paper, bastards): http://citeseer.nj.nec.com/context/18763/0
-j
If we are exchanging one-time pads then this appears to me to shift the weakness to how random your random-number generator really is (find a pattern allowing you to recreate the random number stream then the quantum crypto is useless). The other thing that springs to mind is that for a one-time pad to be totally secure it needs to be as long as the data itself and cannot be reused. This means extra latency as you set up a pad the same size as the data transfer for stateless communication (though for persistant connections I assume there will be a constant out-of-band stream topping up a large buffer to be used between end points).
Phillip.
Property for sale in Nice, France
Being able to understand the technicals of quantum computing, at best, only moderately well, and being remarkably bad at recalling them as anything more than vague and nebulous concepts, I am in no position to even attempt to compare the alternate approaches I have read about over the past several months, but I am wondering if anyone can either answer my questions here, or point me to an article that does. I'm not looking for immense detail; I'd rather just have an answer with basic supporting facts.
What I'm wondering:
One thing that caught my attention is that the quantum dots they used were 180 nm across. That's 0.18 microns, which is larger than current silicon chip lithography processes, which can etch at 0.13 microns, or 130 nm. I realise we're comparing apples and oranges, and that it is superposition (and entanglement, I think) that yields the real power of quantum processors, but I always imagined that a true quantum processor would have much smaller transistor and subsequently die sizes. I know they talk about going as small as 50 nm (0.05 micron), but iirc, IBM is researching (with some success, can someone pull the article?) similarly small lithography techniques for silicon chips too.
Any informed people in the slashdot community who can address these questions? Since I am writing a science fiction novel that integrates quantum computing, and I'd like it to be as realistic as I can potentially make it with educated guessing (hahaha, I hear you smirking already), I'd appreciate any help.
A word can paint a thousand pictures
Yes, it does sound uninformed, and the fact that you're asking it probably means you really know rather little about what quantum computers are really about. The paradox about quantum computers is that they don't need to be faster than their classical counterparts, and in fact, the most of the really promising methods, like the NMR bulk-spin resonance techniques for instance, are far, far slower. These methods based on nuclear spins have clock rates that are measured in kilohertz. Yes, mere thousands of cycles per second. If you use a quantum computer to do the same things a classical computer does, in the same way, you can expect no real improvement. The real advantage in using these computers, which is what makes such a computer "faster" than its classical counterparts is the new paradigm of computing the quantum models of computation allow: that of performing computations on superposed states.
For instance, if you had a register that contained 256 qubits, placed them in an equal superposition of 1 and 0, and performed some calculation on that register, you will have potentially produced 2^256 results, 10^77 or a hundred million million billion billion billion billion billion billion billion results, which is more results than the number of sub-atomic particles in the visible universe! Of course, once you measure your qubits you only get one of these innumerable results, but there are more subtle ways of measuring the qubits that will give you information common to all of the results. That's what all of these algorithms for quantum computers are about.
Essentially, if you had 256 qubits each running at 1 kHz, you would have 10^77 processors running at 1 kHz! Now wouldn't that be faster than any computer in the world if you could use it properly? It's like having a slow computer for every sub-atomic particle in the universe! What's needed now are algorithms that try to find structure in various problems that can exploit this sort of parallelism.
Shor's algorithm, for instance, is able to factor integers and compute discrete logarithms in arbitrary finite fields in O(n^2) time, by using a special technique (the quantum Fourier transform) to cause the results we aren't interested in to interfere destructively and so won't be measured when our superposition collapses. Grover's algorithm, which does unordered searches in O(sqrt(n)) time, leverages quantum parallelism in a similar way.
The real upshot, and a likely SF novel plot that involves quantum computers, comes from the fact that all public-key cryptography in widespread use today depends on the factoring (RSA) and discrete log (El Gamal and elliptic curve techniques) problems. These problems are thought to be intractable using a classical computer, but with Shor's algorithm and a large enough quantum computer, perfectly feasible. Obviously, no one has yet made a quantum computer with more than a handful of qubits (I believe seven qubits is the world record, meaning they could theoretically factor the number 126!), so these schemes are still quite secure. Other practical problems plague implementors. But if someone, somewhere, dreamed up a way to make quantum computing practical (i.e. making a quantum computer with thousands of qubits that could perform calculations stably), all public-key cryptography would fall apart. Whoever invented such a device could potentially break the root certificates of Verisign and other CA's, compute private keys, impersonate every e-commerce site in the world, read all PGP or S/MIME-encrypted email, forge all kinds of digital signatures, create bogus international banking transactions, and so on and so forth. Grover's algorithm would also increase the range of keys that can be feasibly brute forced for symmetric crypto (how much exactly depends on how fast your quantum computer is). Naturally, it would be a device intelligence agencies all over the world would kill to obtain. Ever see Sneakers?
If you're looking for more in-depth information that you can understand without a graduate degree in both physics and computer science (the way most of the preprints on lanl.gov tend to be), you can start by looking here.
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
Good reference - Brassard's Bibliography
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
I know only the basics behind MRI, not the details, but while related I don't think they are dealing with quite the same principle.
As I understand it, the purpose of the large magnetic field in MRI is to force all the nuclear magnetic moments (which are directly related to nuclear spin states) into the same alignment. Then you study the emitted radiation when they relax into a normal normal configuration, or something like that.
In any case quantum computing depends on the entanglement between states which large applied magnetic fields would effectively destroy. So, my impression is that while MRI depends on the presence of distinct spin states, it doesn't concern itself with the type of spin interaction that quantum computing cares about.
PS The article talks about electron spin states, MRI uses nuclear spin states AFAIK. There are however serious attempts to create qubits with nuclear spins.
If you think of a series of coin flips being used to generate a key or one time pad, entanglement basically allows 2 coins to be made, such that when simultaneously flipped, they always land with opposite sides up. You can't control which side yours will land on, so you can't control which side the other will land on. You do know, however, that every time yours lands on heads, the other one landed on tails. So you and your friend each take a coin, and whenever you need to communicate, you both start flipping. One of you bitwise NOTs your data, then you encrypt and send the message. Your friend can then easily decrypt it with his key.
One pair of entangled particles can only be used for one flip, however. So if you want a real key, you need a continuous stream of entangled particle pairs from a single source. Small modifications to this system allow the easy detection of anyone eavesdropping on the entangled particle stream.
Bugrit! Millenium hand and shrimp!