Isn't it a bit premature to compare Google to Bell labs? I mean here are some things that happened at Bell labs: the invention of the transistor, the discovery the cosmic background radiation, a major role in the invention of the laser, the discovery of the mathematical theory of communication, the invention of the solar cell, etc. etc. While I love Google, I don't think they've quite lived up to Bell labs legacy quite yet (but here's hoping they decide to spend billions on fundamental research!)
On the other hand, most (maybe even nearly all) papers I've seen on quantum computing recently have been about using error-correcting codes to fight decoherence.
By, like recently, do you mean since 1995? Quantum error correction (or more generally, the theory of fault-tolreant quantum computation) is one of the most surprising discoveries of the last decade. The next few years are the years where these ideas finally get tried out in the lab. The coming of the quantum machines has begun.
This is not the first controlled-not gate for a quantum computing system but rather the first in this solid state system.
Other implementations of a controlled-not gate (or its close relative, a controlled-phase gate) include:
Caltech Quantum Optics implemented a controlled-phase gate between photons using a strongly coupled atom in a cavity.
Serge Haroche's group implemented a controlled-phase between an atom and a photon using microwave cavities and atomic Rydberg states.
NIST Ion Storage Group: implemented a two qubit gate (which could be turned into a controlled-not) and a four qubit gate using trapped ions.
NMR quantum computing has been implemented by various groups including the biggest quantum computation to date, factoring 15, done by Isaac Chuang's group (IBM and now MIT.)
A proof of principle implementation of a controlled-not in the linear optics quantum computing scheme has been implemented at the University of Queensland.
I'm leaving out quite a few other cool experiments: but the above links should give you a good idea of the what early steps have been taken in quantum computing.
In other news, visitors to the Mountain View cemetery in Altadena, CA were startled when the grave of Richard P. Feynman began to bounce up and down.
"I was walking through the cemetery, trying to figure out where those mountains had disapeared to in the Pasadena smog, when lo and behold I saw this grave just bouncing up and down," said witness Quin El Dorado.
"Well we suspected some strange resonance effect was at work here," said groundskeeper Willie McScottie. "So we noted the dimensions of the grave and did a calculation, and lo and behold, it seems Feynman's grave is in perfect resonance with sounds produced from Bongo drums."
I also saw Michio Kaku on TechTV. He mistakingly said that quantum computers could efficiently multiply two numbers as if this was some kind of amazing feat. Unfortuantely for the (possibly brilliant) Prof. Kaku, people are trying to build quantum computers because they can efficiently factor numbers, not multiply them.
This is about the Government doing background checks into who will be working on it's projects. This is something that will always happen.
No. This is something entirely different that the previous standards used by the NSA (and DOD) as far as I can tell. It is definitely true that background checks are performed for classified work. Working for the NSA will also get you a background check. But traditionally these departments have funded *unclassified* research in which the agencies do not place restrictions on foreign students.
I started to read the article, but then I got all creeped out about the possiblility of a Javascript on the article webpage and couldn't finish the article.
Here's a suggestion: if you don't like the system and don't feel like changing the system, take your bombs and move to Columbia or the middle east.
Yah, that's right, let's send all the evil people elsewhere. Get them out of my site, cus I can't stand them. Send them to places where everyone is, like them, a terrorist. Come to think of it, why don't we send all of our prisoners to Columbia. We don't want them, and, the Columbian's are all a bunch of criminals anyway.
Me, I'd like to think such a blatantly racist and americanocentric statement wouldn't rank a 5 on slashdot, but perhaps I am naive.
If a chip is going to made out of molecular size components, will these molecular size components be reliable? More to the point, if they are not reliable and fault tolerant methods are needed to make them reliable, will they offer and advantage over our current silicon chips?
One of the reasons, it appears to me, that we have reliable classical computers is that these computers use physics to basically perform on the fly error correction. There are physical reasons why classical computers are robust. Take the flow of current through a transistor: when you are talking about a lot of electrons flowing through the components then a few stray electrons flying here or there does not affect the computation (transistion from analog to digital is robust if the analog doesn't fluctuate much). But if you are talking about a few electrons, or (gasp!) single electrons then scattering, tunnelling, etc. seem to me to make such a transitition from analog to digital much less reliable.
The lesson of Moore's law success over the last half century has been (as illuminated by Carver Mead and others) that the operation of our standard silicon based computers gets BETTER as we get smaller. However, it seems to me that there is a point in which this "getting better as we get smaller" will fall apart because the physical laws which allowed reliable components will begin to fail.
This is not to degrade the engineering feat achieved by these researchers which, I must say, is awe inspiring.
Actually I'd have to say that they've had absolutely no success. No one has yet demonstrate free energy. Now this, of course, is a personal evalutation. I've read the stuff on free energy, and thought about their "demonstrations" and it is clear to me that there are huge problems with a lot of the supposed demonstrations.
Of course, just because I have this personal evaluation, and a lot of other scientists would probably agree with me, doesn't mean I'm correct. Perhaps you have missed this, but there aren't many people who hold absolutes sacred in science. Scientists are more than aware (except those pesky members of the church of grand unification) that their laws are not absolutes and may not be fully correct. However, if they had to take a bet, at any given moment that a phenonmenon which they think they understand particularly well will behave according to the laws they know, they'd be rich off the wagers.
Furthermore, to press the issue further, I'd just like to point out that the "three laws" are actually not laws as in postulates but more like derived concepts. This is because thermodynamics is best viewed as coming from stastical mechanics which has its microscopic basis in quantum mechanics. In fact, things like the infamous second law are notoriously hard to think about for nonequilibrium and microscopic systems where thermodynamics is a poor approximation. So if you are going to attack something, you'd probably better go after quantum mechanics (more specifically quantum field theory) or the physical theories that lie on top of this quantum edifice.
but it seems to me that the "reward" for my efforts I would get in research/education are less than when I would work for a big company, earning a lot of money
Which is the reason most researchers feel that the research itself is the reward.
The real accomplishment was using a Bose-Einstein condesate to very easily construct and arrangement of atoms that would otherwise be technologically very hard
Yep. While, as mentioned, you could do this with any supercold gas, the important point is that one should be able to use this to create uniformly populated optical lattices. This would be great for doing things like [hype mode on]building a quantum computer![hype mode off]
Also neat is that this looks like a nice clean system for studying a quantum phase transition, but calling it a new state of matter is a bit odd. As far as I know, the observation of a Mott Insulator is nothing new...though in the context of supercold atomic systems this is probably new.
Interestingly, when I searched Google for Mott Insulator, this experiment was the first to come up! Wow.
Well there is a bit of a difficulty in explaining exactly where the computational power of a quantum computer comes from. Kind of like asking where the power of a classical computer comes from (and don't say "from the power company" damnit (yes, I'm from California)).
But the "power" of quantum algorithms over classical algorithms makes itself clear when you realize that all efficient quantum algorithms make use of a COLLECTION of quantum systems. When you take the polarization of a single photon and use polarization filters you essentially have a single quantum bit of information corresponding to the two polarizations. But in order to make a quantum algorithm, you need to put a bunch of these qubits together and they must interact in a non-trivial manner. Thus you need to get someway for the polarization of one photon to interaction with the polarization of another photon. This is really a pain in the ass to do without destroying the photon or the coherence of the polarizations.
So I guess what I am saying is that when you take a bunch of quantum systems and build a quantum algorithm, the power of the algorithm comes from the dynamics of the interaction of multiple quantum systems.
The fact that quantum computers are probabilistic and rely have a "collapse" of the wavefunction at the end of the computation are sort of secondary to the issue of where the power comes from.
As has been pointed out by many posters already, this is not what nearly all researchers would call a quantum computer. A universal quantum computer, from a physicists perspective, is a computer built with pieces which obey quantum mechanics AND can be used to EFFICIENTLY simulate the effects of systems obeying quantum mechanics. This EFFICIENCY condition is extremely important, because, for instance, your classical computer can simulate quantum physics...it just takes it a hell of a long time for most reasonably sized problems!
The device described (poorly) in the article fails to achieve an efficient simulation of quantum systems because the number of frequencies needed in order to perform a given simulation will scale exponentially in the size of the quantum computer being simulated. Albeit technologically interesting, the computation performed by the experiment is not something which a classical computer cannot do as efficiently.
But what really troubles me is the quote attributed to Walmsley in the article: "We wanted to show that the implementations which have been done with quantum computing have an exact analogy that is just as effective in light-based processes," says Walmsley.
Just as effective?! That is a just not true. Is this a case of a scientist being quoted out of context or is it a case of a scientist who doesn't understand the issue?
Yes, MTIOQC (my thesis is on quantum computing), so I feel like I have a little bit vested in this issue. Being so biased, I hope that this is just an out of context mistake.
I would like to think that our enlightment grows with time, but every new article I read about quantum computing research seems to be filled with more and more hyperbole (oh do I hate the words "paradigm shift" and "synergy") and less and less good science. Don't get me wrong, I think quantum computing has a promising future both in actual future practice as well as in helping shed light on areas of physics (We all learned that quantum mechanics destroyed the computer-like determinism of Newtonian mechanics, but now we think that, while the universe is not a big classical computer, the universe may be a big quantum computer!), but irresponsible press releases drive me bonkers.
There is a system called the McEliece system which is based on algebraic coding theory and I believe is NP-complete. Last I remember hearing, there were some attacks on McEliece, but I think the jury is still out?
There is also a version of the knapsack-based (i.e. NP-complete) systems (Chor-Rivest, I think it is called) which hasn't been broken last I recall. And I do remember someone telling me that Chor-Rivest isn't aided by an efficient discrete logithm algorithm (which quantum computers DO provide!)
Yet. Quantum computers. There's one technology I hope never comes real in my lifetime. Looks like I'll be disappointed, I had no idea they had come this far.
Why? Because it will mean an end to public-key cryptography forever.
What?! This just is absolutely FALSE!
(1) Public key cryptography is secure because of the difficulty of a particular computational task. For example, in RSA, that task can be mapped onto factoring numbers
(2) Quantum computers provide algorithmic speedup of some algorithmic tasks. For example, quantum computers can factor numbers efficiently.
Now (1) plus (2) does NOT imply all public key cryptography schemes are insecure because not all public key cryptography schemes are built on problems that quantum computers are known to be able to handle efficiently. For example, it is possible (though encoding and decoding times are ugly, I've been told) to use an NP-complete problem as the computational roadblock in codebreaking. As of today, we do now know how to solve NP-complete problems efficiently on either a classical or a quantum computer.
And remember, the security of public key cryptography like RSA is not "proven": it relies on the "difficulty" of a computational task. People really believe it is difficult to factor numbers classically. Why? Because they have been banging their heads up against the problem for quite a few years. But proof by exhaustion is no proof at all: just evidence.
So the main jist is: public key cryptography as a whole will NOT be destroyed by building quantum computers. Certain schemes which you bought into because you believed that factoring is hard WILL be broken, however.
Finally I would like to point out that quantum cryptography is a way to establish a secure key distribution. The security of this scheme is based not on some conjectured hardness of a problem, but instead on the belief that quantum mechanics governs the physics of the universe.
Christianity is silent on the possiblity of extraterrestrial, material life. Therefore, our finding or not finding it is irrelevant to the truth and teaching of Christianity.
I wonder what would happen to your faith if humanity encountered a material life which said: "your Christian doctrine is bull-pucky". Would that change the relevance of the truth and teaching of Christianity?
I guess you would then just shift to the "these material beings are God's test of my faith".
Mathematicians have long known that a single contradiction can logically lead you to prove all contradictions. But religion has know this for thousands of years: use faith in your arguement and you are set!
dabacon
(working on cloning Jesus from the shroud)
Slashdot Mirror
Bruce needs to read more before he posts stuff like this: http://scienceblogs.com/pontiff/2008/03/shor_calculations.php
You are mistaken. Elliptical curve cryptography is broken by quantum computers. And yes, I am a quantum physicist.
Isn't it a bit premature to compare Google to Bell labs? I mean here are some things that happened at Bell labs: the invention of the transistor, the discovery the cosmic background radiation, a major role in the invention of the laser, the discovery of the mathematical theory of communication, the invention of the solar cell, etc. etc. While I love Google, I don't think they've quite lived up to Bell labs legacy quite yet (but here's hoping they decide to spend billions on fundamental research!)
This is not the first controlled-not gate for a quantum computing system but rather the first in this solid state system.
Other implementations of a controlled-not gate (or its close relative, a controlled-phase gate) include:
Caltech Quantum Optics implemented a controlled-phase gate between photons using a strongly coupled atom in a cavity.
Serge Haroche's group implemented a controlled-phase between an atom and a photon using microwave cavities and atomic Rydberg states.
NIST Ion Storage Group: implemented a two qubit gate (which could be turned into a controlled-not) and a four qubit gate using trapped ions.
NMR quantum computing has been implemented by various groups including the biggest quantum computation to date, factoring 15, done by Isaac Chuang's group (IBM and now MIT.)
A proof of principle implementation of a controlled-not in the linear optics quantum computing scheme has been implemented at the University of Queensland.
I'm leaving out quite a few other cool experiments: but the above links should give you a good idea of the what early steps have been taken in quantum computing.
In other news, visitors to the Mountain View cemetery in Altadena, CA were startled when the grave of Richard P. Feynman began to bounce up and down.
"I was walking through the cemetery, trying to figure out where those mountains had disapeared to in the Pasadena smog, when lo and behold I saw this grave just bouncing up and down," said witness Quin El Dorado.
"Well we suspected some strange resonance effect was at work here," said groundskeeper Willie McScottie. "So we noted the dimensions of the grave and did a calculation, and lo and behold, it seems Feynman's grave is in perfect resonance with sounds produced from Bongo drums."
I also saw Michio Kaku on TechTV. He mistakingly said that quantum computers could efficiently multiply two numbers as if this was some kind of amazing feat. Unfortuantely for the (possibly brilliant) Prof. Kaku, people are trying to build quantum computers because they can efficiently factor numbers, not multiply them.
This is about the Government doing background checks into who will be working on it's projects. This is something that will always happen.
No. This is something entirely different that the previous standards used by the NSA (and DOD) as far as I can tell. It is definitely true that background checks are performed for classified work. Working for the NSA will also get you a background check. But traditionally these departments have funded *unclassified* research in which the agencies do not place restrictions on foreign students.
Dabacon
Gerard Milburn is known around campus as the prof who traps ions in the basement of the physics building.
;)
Funny, that, considering he is a theorist
dabacon
would require strategic thinking, game theory, and multitasking
Damnit, my Knights keep getting suckered away from the Nash equilibirum!
dabacon
I started to read the article, but then I got all creeped out about the possiblility of a Javascript on the article webpage and couldn't finish the article.
dabacon
Here's a suggestion: if you don't like the system and don't feel like changing the system, take your bombs and move to Columbia or the middle east.
Yah, that's right, let's send all the evil people elsewhere. Get them out of my site, cus I can't stand them. Send them to places where everyone is, like them, a terrorist. Come to think of it, why don't we send all of our prisoners to Columbia. We don't want them, and, the Columbian's are all a bunch of criminals anyway.
Me, I'd like to think such a blatantly racist and americanocentric statement wouldn't rank a 5 on slashdot, but perhaps I am naive.
dabacon
Yes, this is exactly my point. If you need 10^3 faulty components, then why not just use something that is 10^3 larger but robust????
Dabacon
Here is a question for all ya smart /.ers:
If a chip is going to made out of molecular size components, will these molecular size components be reliable? More to the point, if they are not reliable and fault tolerant methods are needed to make them reliable, will they offer and advantage over our current silicon chips?
One of the reasons, it appears to me, that we have reliable classical computers is that these computers use physics to basically perform on the fly error correction. There are physical reasons why classical computers are robust. Take the flow of current through a transistor: when you are talking about a lot of electrons flowing through the components then a few stray electrons flying here or there does not affect the computation (transistion from analog to digital is robust if the analog doesn't fluctuate much). But if you are talking about a few electrons, or (gasp!) single electrons then scattering, tunnelling, etc. seem to me to make such a transitition from analog to digital much less reliable.
The lesson of Moore's law success over the last half century has been (as illuminated by Carver Mead and others) that the operation of our standard silicon based computers gets BETTER as we get smaller. However, it seems to me that there is a point in which this "getting better as we get smaller" will fall apart because the physical laws which allowed reliable components will begin to fail.
This is not to degrade the engineering feat achieved by these researchers which, I must say, is awe inspiring.
Dabacon
and some have had a good degree of success
Actually I'd have to say that they've had absolutely no success. No one has yet demonstrate free energy. Now this, of course, is a personal evalutation. I've read the stuff on free energy, and thought about their "demonstrations" and it is clear to me that there are huge problems with a lot of the supposed demonstrations.
Of course, just because I have this personal evaluation, and a lot of other scientists would probably agree with me, doesn't mean I'm correct. Perhaps you have missed this, but there aren't many people who hold absolutes sacred in science. Scientists are more than aware (except those pesky members of the church of grand unification) that their laws are not absolutes and may not be fully correct. However, if they had to take a bet, at any given moment that a phenonmenon which they think they understand particularly well will behave according to the laws they know, they'd be rich off the wagers.
Furthermore, to press the issue further, I'd just like to point out that the "three laws" are actually not laws as in postulates but more like derived concepts. This is because thermodynamics is best viewed as coming from stastical mechanics which has its microscopic basis in quantum mechanics. In fact, things like the infamous second law are notoriously hard to think about for nonequilibrium and microscopic systems where thermodynamics is a poor approximation. So if you are going to attack something, you'd probably better go after quantum mechanics (more specifically quantum field theory) or the physical theories that lie on top of this quantum edifice.
dabacon
but it seems to me that the "reward" for my efforts I would get in research/education are less than when I would work for a big company, earning a lot of money
Which is the reason most researchers feel that the research itself is the reward.
dabacon
The real accomplishment was using a Bose-Einstein condesate to very easily construct and arrangement of atoms that would otherwise be technologically very hard
Yep. While, as mentioned, you could do this with any supercold gas, the important point is that one should be able to use this to create uniformly populated optical lattices. This would be great for doing things like [hype mode on]building a quantum computer![hype mode off]
Also neat is that this looks like a nice clean system for studying a quantum phase transition, but calling it a new state of matter is a bit odd. As far as I know, the observation of a Mott Insulator is nothing new...though in the context of supercold atomic systems this is probably new.
Interestingly, when I searched Google for Mott Insulator, this experiment was the first to come up! Wow.
Dabacon
It is nice that you put quotes around "National Security".
Dabacon
OK, Anonymous Coward, you keep using your RSA then.
As for me, I'm betting on good old human ingenuity.
dabacon
Well there is a bit of a difficulty in explaining exactly where the computational power of a quantum computer comes from. Kind of like asking where the power of a classical computer comes from (and don't say "from the power company" damnit (yes, I'm from California)).
But the "power" of quantum algorithms over classical algorithms makes itself clear when you realize that all efficient quantum algorithms make use of a COLLECTION of quantum systems. When you take the polarization of a single photon and use polarization filters you essentially have a single quantum bit of information corresponding to the two polarizations. But in order to make a quantum algorithm, you need to put a bunch of these qubits together and they must interact in a non-trivial manner. Thus you need to get someway for the polarization of one photon to interaction with the polarization of another photon. This is really a pain in the ass to do without destroying the photon or the coherence of the polarizations.
So I guess what I am saying is that when you take a bunch of quantum systems and build a quantum algorithm, the power of the algorithm comes from the dynamics of the interaction of multiple quantum systems.
The fact that quantum computers are probabilistic and rely have a "collapse" of the wavefunction at the end of the computation are sort of secondary to the issue of where the power comes from.
dabacon
As has been pointed out by many posters already, this is not what nearly all researchers would call a quantum computer. A universal quantum computer, from a physicists perspective, is a computer built with pieces which obey quantum mechanics AND can be used to EFFICIENTLY simulate the effects of systems obeying quantum mechanics. This EFFICIENCY condition is extremely important, because, for instance, your classical computer can simulate quantum physics...it just takes it a hell of a long time for most reasonably sized problems!
The device described (poorly) in the article fails to achieve an efficient simulation of quantum systems because the number of frequencies needed in order to perform a given simulation will scale exponentially in the size of the quantum computer being simulated. Albeit technologically interesting, the computation performed by the experiment is not something which a classical computer cannot do as efficiently.
But what really troubles me is the quote attributed to Walmsley in the article:
"We wanted to show that the implementations which have been done with quantum computing have an exact analogy that is just as effective in light-based processes," says Walmsley.
Just as effective?! That is a just not true. Is this a case of a scientist being quoted out of context or is it a case of a scientist who doesn't understand the issue?
Yes, MTIOQC (my thesis is on quantum computing), so I feel like I have a little bit vested in this issue. Being so biased, I hope that this is just an out of context mistake.
I would like to think that our enlightment grows with time, but every new article I read about quantum computing research seems to be filled with more and more hyperbole (oh do I hate the words "paradigm shift" and "synergy") and less and less good science. Don't get me wrong, I think quantum computing has a promising future both in actual future practice as well as in helping shed light on areas of physics (We all learned that quantum mechanics destroyed the computer-like determinism of Newtonian mechanics, but now we think that, while the universe is not a big classical computer, the universe may be a big quantum computer!), but irresponsible press releases drive me bonkers.
dabacon
There is a system called the McEliece system which is based on algebraic coding theory and I believe is NP-complete. Last I remember hearing, there were some attacks on McEliece, but I think the jury is still out?
There is also a version of the knapsack-based (i.e. NP-complete) systems (Chor-Rivest, I think it is called) which hasn't been broken last I recall. And I do remember someone telling me that Chor-Rivest isn't aided by an efficient discrete logithm algorithm (which quantum computers DO provide!)
Dave Bacon
Yet. Quantum computers. There's one technology I hope never comes real in my lifetime. Looks like I'll be disappointed, I had no idea they had come this far.
Why? Because it will mean an end to public-key cryptography forever.
What?! This just is absolutely FALSE!
(1) Public key cryptography is secure because of the difficulty of a particular computational task. For example, in RSA, that task can be mapped onto factoring numbers
(2) Quantum computers provide algorithmic speedup of some algorithmic tasks. For example, quantum computers can factor numbers efficiently.
Now (1) plus (2) does NOT imply all public key cryptography schemes are insecure because not all public key cryptography schemes are built on problems that quantum computers are known to be able to handle efficiently. For example, it is possible (though encoding and decoding times are ugly, I've been told) to use an NP-complete problem as the computational roadblock in codebreaking. As of today, we do now know how to solve NP-complete problems efficiently on either a classical or a quantum computer.
And remember, the security of public key cryptography like RSA is not "proven": it relies on the "difficulty" of a computational task. People really believe it is difficult to factor numbers classically. Why? Because they have been banging their heads up against the problem for quite a few years. But proof by exhaustion is no proof at all: just evidence.
So the main jist is: public key cryptography as a whole will NOT be destroyed by building quantum computers. Certain schemes which you bought into because you believed that factoring is hard WILL be broken, however.
Finally I would like to point out that quantum cryptography is a way to establish a secure key distribution. The security of this scheme is based not on some conjectured hardness of a problem, but instead on the belief that quantum mechanics governs the physics of the universe.
Dave Bacon
Yah the title is mind boggling off target.
How about Standard model demonstrated to be substandard
or A good reason never to call your model the standard model
or Experiment guarantees theoretical physicists jobs for the next twenty years
dabacon
Christianity is silent on the possiblity of extraterrestrial, material life. Therefore, our finding or not finding it is irrelevant to the truth and teaching of Christianity.
I wonder what would happen to your faith if humanity encountered a material life which said: "your Christian doctrine is bull-pucky". Would that change the relevance of the truth and teaching of Christianity?
I guess you would then just shift to the "these material beings are God's test of my faith".
Mathematicians have long known that a single contradiction can logically lead you to prove all contradictions. But religion has know this for thousands of years: use faith in your arguement and you are set!
dabacon
(working on cloning Jesus from the shroud)