IBM Builds A Limited Quantum Computer

phr1 writes "IBM has announced and Yahoo has noted that the first working implementation of Shor's factoring algorithm. Using NMR techniques they built a seven-qubit quantum computer and factored the number 15 into the factors 3 and 5. This is by far the most complicated quantum computation ever done. It's quite an amazing feat--many people thought quantum computing was just a theoretical curiosity and Shor's algorithm could never be implemented in practice."

Comments

Frightening implications

[krackbebe]

If a private sector company has been able to climb the steep hill that is quantum computing, how far has the US govt been able to get with their nearly unlimited budget?

It has been widely acknowledged that such agencies as the NSA have been at least a decade or more ahead of the private sector. The first govt to get a working quantum computer not only has unbreakable encryption, they are able to read any code of foreign nations. The stakes are incredible!

Soon, they will be watching all of us. Better read 1984 quickly my fellow citizens!

Re:Frightening implications

[actappan]

Good science projects only get the shaft if they have nothing to do with:

• Killing the other guy in new and interesting ways.
  
• Reading the other guy's mail.
  
• Stealing from the other guy.
  
• Reading your own guys' mail.
  
• Stealing from your own guys.
  
• Killing your own guys in new and interesting ways.
  

Re:Frightening implications

[El_Nofx]

1. The us government does not have an unlimited budget.

2. Most meaningful research comes from the private sector (bell labs and the like) with a few exceptions (Darpa)

3. Even if the government had quantum computer level encription it couldn't get it's self organized enough to use it for more then maybe presidential level communication.

Re:Frightening implications

[internic]

While I have also often heard stories of the NSA having much more advanced equipment and techniques than the private sector, or at least than the non-classified private sector, in the case of quantum computing this is unlikely. First, it's a relatively new subject. Shore's algorithm, for example, was only discovered in the 80's. There really hasn't been enough time for them to get so far ahead. Second, the NSA is full mostly of mathematicians and computer scientsts, not physicists, so they really don't have the right staff for that. Third, most of the academic research is funded by the NSA.

Finally, though it's hard to say exactly how far this technology is from being useful (or alternately the probability that it will EVER be useful), it is probably safe to say it will be quite a while from now. Moreover, it is probably also safe to say that it only gets harder from here. Larger computations will involve the same problems as these only on larger scales plus a whole new, tougher, slew of problems that these avoid. These are chiefly quantum decoherence and entangling large numbers of quantum states.

Quantum decoherence is the loss of the special quantum information (quantum phase relations) that allows quantum computers to do their funky magic. This happens over time in any system that has any interaction with the outside world. I think these small calculations largely avoid this problem because they are reasonably fast. Larger ones involve more steps and thus will run up against these problems. Some error correcting quantum codes have been developed, but these involve even more qubits, which exaserbates the other problems, and are still largely in the formative stages.

The other big hurdle is entangling much larger numbers of particles in one state. These take advantage of the interactions between different nuclei in the same molecule. Once you need many more qubits, you will need to come up with a more general scheme for entangling the quantum states, because it's unlikely that you'll be able to engineer a molicule for the purpose. Also, the bigger you make your system, the more strongly it interacts with the outside world and the worse decoherence becomes....Life's a bitch, ain't it?

So, I think this is really exciting and quantum computers have great promise, but I don't expect to have a quantum co-processor in my PC any time soon, nor do I really think it's likely that the NSA has a quantum supercomputer sitting in the back room decrypting my credit card information.

Re:Frightening implications

[KjetilK]

This is an interesting point. We discussed this to some length at the International Conference for Physics Students this summer.

The core question is: Can a real, working quantum computer be built in secrecy?

IMHO, it is very unlikely. It has to do with how science works. A few things can pop out straight from a brilliant idea, and can be implemented based on that idea alone. This is, however, very, very uncommon. Even the most brilliant minds needs feedback from their peers to get anywhere. You need critisism, even strong opposition, to fine-tune your ideas and your arguments. This is what the greater scientific community provides.

In closed projects, even if you hire the best minds, you'll get inbreed, you will not get the same level of critisism, and soon you will most probably paint yourself into a corner.

So, while there are examples of projects that have been developed in secrecy that actually work well, most real science has to be done in the open.

Arguably, the most advanced project that we know of that was conducted in secrecy is the Manhattan project. However, building a nuclear bomb wasn't really that difficult. All the basic science was well understood in 1941, it was just engineering left. The brilliant minds found it rather boring. It was completed, and it was kept secret because of the war, there existed very strong reasons for the people who developed it to keep it secret. Hardly any such reasons exist today. A quantum computer will be so important to science and technology, I don't think you can have a larger group of brilliant minds keep it secret for very long. They would want to have the advancement of science going, and beside, they want the nobel prize.

I'm not really frightened. I'd really like to see quantum computers. Yeah, it will make PKI as we know it obsolote, and it really needs adressing fast. I'm not aware of any algoritms that can make reasonably strong encryption on a classical computer that can withstand an attack from a quantum computer, but we'll need that to be reasonably safe while we're waiting for quantum computers to be widespread enough for everybody to use. Anybody know of efforts in this regard?

Re:Frightening implications

[Angst Badger]

Finally, though it's hard to say exactly how far this technology is from being useful (or alternately the probability that it will EVER be useful), it is probably safe to say it will be quite a while from now. Moreover, it is probably also safe to say that it only gets harder from here.

Certainly. On the other hand, if you had looked at the thermionic-valve computers of the 1940's, it would have been hard to imagine the Atari 2600, much less a Beowulf cluster of quad-Xeons.

nor do I really think it's likely that the NSA has a quantum supercomputer sitting in the back room decrypting my credit card information.

Nor should you. However, given the way the NSA has largely backed off any serious efforts to outlaw public-key cryptography, it is likely that they have either the brute force computing power or classified algorithms to crack it, so it's not necessary to imagine exotic computing technology. Besides, if an agency like the NSA really wants information from you badly enough, you'll end up giving it to them, Winston.

Shouldn't there be a +1 Deeply Paranoid moderation option?

Re:if a quantum computer takes the same time

[Anml4ixoye]

Mainly because of the number of molecules it takes to perform that feat. "IBM chemists designed and made a new molecule that has seven nuclear spins" - exactly enough to solve the simple factor. You need many more spins than that to perform complex calculations.

But once the molecules are put together and they can control them properly, then nothing really stops it. That is why they say that a fundamental change in cryptography is on the horizon.

similar has been done before

[Phork]

2 years back i heard someone(i belive it was bruse schneir), say that the NSA or los alamos had built a quanum computer, and it could factor the number 7, down to 1 and 7, not to hard. but still an impressive feat.

OS

[geekoid]

Now all I need to do is write a proprietary OS for it, and convince IBM to let me keep the rights!

I'm thinking of calling my company "Quantumsoft"

And my software would be able to slow the quantum computer to a crawl!

still a long way to go...

[dummkopf]

even though we can factor 15 == 3*5, we are still far away from useful quantum computer applications. the problem is that the coherence time of the atoms is fairly short and only O(10^3) computations can be performed before the system is decoherent. there are many interesting (but rather technical) papers about this subject and how to build quantum computers with quantum dots or any other solid state devices. you can get a glimpse of what is going on at the front of physics at http://xxx.lanl.gov/. just search for quantum+computing...

anyone got a patch...

[merlyn]

... for GnuPG to have 100000 bit keys? Quickly?

IBM's largest computer ever

[charon_on_acheron]

From the Yahoo article:
"Previously the largest computer IBM had built was based on five atoms."

So what about the 2 ton behemoths everyone's been buying for years? ;-)

Re:IBM's largest computer ever

[Hank Reardon]

So what about the 2 ton behemoths everyone's been buying for years? ;-)

Big fucking atoms...

Re:IBM's largest computer ever

[iabervon]

Those were based on only five atoms. The 2 tons were for the case, the power supply, the monitor, the fans, those sturdy IBM keyboards, the user manual, and so forth. But all of the really clever design was in those five atoms.

An Introduction...

[GFish4]

My brother found this for me not too long ago. The math involved can get rather intense, but I think it 's worth pointing out:

An Introduction to to Quantum Computing for Non-Physicists - Available in PDF, PostScript, and others.

If you do a google search, you probably can find it elsewhere, also.

--GFish4

Crud!

[Pathos78]

And I thought my 4-bit key's were safe!
Damn the relentless progress of computing!

Re:Could quantum computing ever become general pur

[Logic Bomb]

I don't think the point was that this molecule could only factor 15 (well, maybe, but read on). The point is that they needed to make a molecule with 7 atoms that could interact in a certain way. To do bigger problems, they will need to design a molecular structure that fits many more atoms together. However, that structure will be able to solve *any* problems possible within its capacity.

My boss says ...

[benedict]

... "They should have asked me to do it. They could
have saved a lot of money."

Unfortunately NMR quantum computing has limits

[Spooky Possum]

The technique used here (NMR) is probably the best understood way of doing quantum computing (a lot of the basics are dragged straight out of medical imaging technology). Unfortunately it has a very fundamental limitation: the initialisation phase scales exponentially. Everything else is practical, but for every qubit you add you need to add exponentially more molecules to your system. Since you start off with a "billion billion" molecules you get a good head start, but systems much beyond seven qubits become very difficult and anything practical is impossible.

Of course almost all current quantum computing schemes have fatal flaws and NMR is well ahead of everyone else (with the possible exception of ion trapping). However in most other schemes the flaws aren't fundamental (just really, really, difficult to fix).

Disclosure: I have worked on a competing quantum computing scheme (neutral atoms). It's crap too.

Re:Unfortunately NMR quantum computing has limits

[nihilogos]

Actually one of the flaws in NMR quantum computation is that the signal strength used for measurement decreases exponetially with the addition of more qubits. That's pretty fundamental.

Los Alamos and "federal researchers"

[Anonymous Coward]

Los Alamos built a three-qubit quantum computer a while back. I don't have references, except a few mentions in other news articles. Sorry.

But in March of 2000, a group claimed to have built a 7-qubit quantum computer. It's based on some different techniques than previously used, but the researcher said that the techniques can't go past 15 qubits. Check it out at:

http://www.wired.com/news/technology/0,1282,3512 1, 00.html

Meow

[KarmaBlackballed]

If you put a cat inside this computer, will it die?

Another article at News.com

[A Commentor]

It's also discussed at news.com .

You Heard It Here First...

[cybrpnk]

Looks like the number of qbits available in a quantum computer is doubling every 18 months. The article notes the 2 qbit computer was built in 1998, the 4 qbit unit in August 2000 and now a 7 qbit computer in December 2001....they've still got another couple of months to get the 8th qbit....

Re:You Heard It Here First...

[Traa]

please tell us you heard some important dude at IBM claim this growth patern first....

because I'm not looking forward to calling it cybrpnk's law

Almost there!

[Black Parrot]

7 Qbits already? That's great! No one should ever need more than 640 Qbits.

The End of Asymmetric Key Distribution

[Muerte23]

As probably most people here realize, the advent of sufficiently strong quantum computers renders obsolete every encryption scheme. Except, of course, then Verdam cypher or One Time Pad.

At JPL, among, there is a group working on quantum key distribution. The aim is to have entanged photons distributed at the same rate (or almost the same rate) as the data, and to use this as a crypto key that is totally unbreakable. Untappable, unbreakable, impervious.

Doesn't it strike anyone as strange and cool that quantum computers and quantum key distribution are coming to fruition at almost exactly the same time?

muerte

Re:The End of Asymmetric Key Distribution

[zCyl]

I think that most current crypto algorithms are based on factoring primes

When you factor your first prime, I recommend publishing the result...

Re:The End of Asymmetric Key Distribution

[frankie]

The whole point of quantum encryption (which is completely a different process than quantum computing) is that observing the quantum causes the quantum to change. Therefore, the man in the middle will disrupt the transmission and be detected instantly.

Quantum encryption, when used correctly, is really truly mathematically proven to be unbreakable by any means.

not true

[phr1]

Quantum computing could conceivably obsolete public key (asymmetric) cryptography. However it doesn't break conventional cryptography. A sufficiently strong quantum computer can turn an O(f(n)) computation into O(f(sqrt(n)) but that's all. For example, it could break a 56-bit key in 2**28 steps instead of 2**56 steps. That means 128-bit keys could conceivably be broken by quantum computers (in 2**64 steps). However, by doubling the key length (say to 256 bits) you get the security against quantum computers that you now get against conventional computers.

Old news

[sharkey]

7 qubits!?!? Sheesh, Noah's Ark was 300 qubits long, by 50 wide, by 30 high. And seven is supposed to be impressive thousands of years later?

Re:Downsides....

[ZigMonty]

(1) Any government agent could crack your encryption...after all, a quantum computer could crack a fifteen thousand letter password in like two seconds. (of course, not for PGP, since it is based on unsolvable algaebraic formuli)

How is it based on unsolvable algebra? It's based on HARD algebra. The only reason public key encryption is currently secure is that it is much easier to multiply than factor. It may take a few seconds to encypt something but, without the private key, it takes a long time to crack on *current computers*. It *can* be done given enought grunt, see distributed.net. These Quantum computers (or their successors) can theoretically crack an encryptred message in about the same time as if you had the private key. It makes PGP, GPG, SSH, SSL etc (ie. all of them) about as secure as rot-13.

If we don't get a more secure encryption system out before the real quantum big guns come out, e-commerce etc is basically stuffed.

Re:that's not much of an upshot then...

[tomstdenis]

Which gets back to the original point. Quantum computing is just a way to sieve multiple solutions in parallel. Much akin to the idea of DNA Computing.

Think of a beowolf cluster of 1,000,000 athlons at 1.4ghz compared to a single 486 60mhz. The time per solution is hugely different even if the exact same binary program is used to solve the problem.

Also QC does not break any barriers related to NP != P. If a QC computer works this does not change. It just means some NP problems become faster to solve.

Tom

Re:not in general

[phr1]

Just some specific problems like factoring.
For GENERAL brute force search type problems
the speedup is as I described. See the articles
at qubit.org for more info.

You're exactly right and wrong!

[HiredMan]

You're right that the NSA knew about Differential Cryptanalysis years before anyone. I extrapolated this largely using the same facts - but if you read _AC_ carefully they openly acknowledge this.

But you're wrong in the fact that DES IS resistant to DC. The bit S-box design the NSA gave IBM are designed to make it STRONGER against DC NOT weaker.

"As in choosing the key length , another of the NSA'a design criteria was based on making the algorithm [DES] resistant to differential cryptanalysis..." _AC_ first edition Schneier page 238

If you want to bust the NSA's chops complain that they made the key length go from 128 to (effectively) 56 bits. Now that hurt...

=tkk

Fool!

[Jebediah21]

You should have used 5-bit keys like me.

Re:if a quantum computer takes the same time

[stevelinton]

It doesn't. The thing about Shor's algorithm is that, as initially written up, it factors an L bit number on a 3L q-bit quantum computer in polynomial time (O(L^3), I think). Obviously IBM have tweaked it a bit to get down from 12 (3*4) to 7 qbits, but even so, going from 4 bits to say 1024 would require 256 times as many qbits (the hard part) and 256^3= 16 million times as much time (not a big problem).

In contrast existing non-quantum techniques take O(e((log L)^(2/3)*(L)^(1/3))) time on a computer of fixed word size. To go from 4 bits to 1024 increases the run time by a factor of something like 10^18.

More to the point, on quantum computers, the race between prime finding, and so key pair generation, and factoring and so code-breaking is much less uneven.