IBM Develops Quantum Computer 180
JSC writes: "IBM has developed a quantum computer consisting of five atoms that work as the processor and memory. It's a nice advance of the state of the art...unfortunately, we won't see them on the shelves for about 20 years." Update: 08/15 06:49 PM by H :Check out the official IBM release - thanks to netMonkey for the update.
Finally (Score:1)
Even the samurai
have teddy bears,
and even the teddy bears
Perhaps IBM along with Ziggy... (Score:4)
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moving right along (Score:1)
Can you imagine... (Score:2)
Come on, I deserve karma for posting it on-topic and using my real name
Hmm..... Quantum Computing... (Score:2)
I want one, but.. (Score:2)
Key cracking (Score:3)
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5 atoms? (Score:1)
I can see some potential problems (Score:1)
Re:Can you imagine... (Score:2)
5 Atoms? (Score:5)
New Use for Pocket Lint = Quantum Computing (Score:1)
The ultimate Quake cheat! (Score:2)
Does that mean I'll be able to be everywhere at once? Of course that could work both ways -- being everywhere presents a big target...
Cryptography (Score:1)
More details (Score:2)
--Chouser
Programming Quantum Computers (Score:4)
Nice stuff they've got, but... (Score:1)
So when's the PSC [psc.net] getting one?
Innovations galore! (Score:3)
"Axiom"?! (Score:1)
Perhaps a quantum processing unit (QPU?) would be more useful as a self-contained accelerator card for a traditional computer.
Which brings us to something I've always wondered: How does does one (efficientl) program a quantum computer? Wouldn't the time spent configuring the atoms with their billions of values exceed the time saved by the quantum operations?
Don't Hold Your Breath (Score:1)
Re:Key cracking (Score:1)
Heisenberg compensator (Score:2)
Oops! (Score:2)
Re:5 atoms? (Score:2)
Just don't sneeze.
Predictions (Score:5)
PigPig Gates says: We'll never need more than 640 protons.
PigPog's Uncertainty Principle: We may know where the computer is or which direction it just blew off the table, but never both at the same time.
Yeah but... (Score:3)
Xentax
What are the real-world applications? (Score:1)
Also, how are we going to program these baby's? Surely current techniques, languages etc. will all be insufficient?
Questions, questions.
Also, while I'm at it, This [qubit.org]is a good place for a quantum computing primer.
Re:Key cracking (Score:1)
No more smaller CPUs? (Score:1)
So after Quantum Computers, Computers would only get bigger and bigger.
It sounds like a strange idea.
The distance between insanity and genius is measured only by success.
Re:Key cracking (Score:1)
This will allow the government to crack 5-bit encryption in fractions of a second! Think of the repercussions for privacy! No longer will the NSA have to brute force their way through the entire keyspace (more than 30 possible keys!)
Seriously, though, if this follows the usual track of computer hardware development, sooner than most expect, there will be an operating model. This would enable the NSA to crack 128 bit encryption fast enough to seriously change the state of privacy.
I have enough sense to make 4096 bit keys whether it's currently necessary or not, but for most people, 128 bit is all they see as needed. This is coded into security apps too much already. In ten years how many people will still be using 128 bit as the "accepted standard", especially with the NSA standing in the way every chance it gets.
Billions of calculations at once.. (Score:1)
New Slogan (Score:1)
Why would we EVER see them on shelves? (Score:1)
Why the hell would any normal person ever need something like this? "Ooooh daddy, can I get the QZ-5900 please?!?! I want to calculate solar radiation flux! I want to simulate nuclear detonations! I want to solve the traveling salesman problem for 29 billion routes!"
These are the kinds of problems that quantum computers are geared to compute. Not for playing games, not for doing spreadsheets, and definitely not anything for the store shelves. The only thing that might even tangentially intersect with the common interests is decryption, and I assure you the government will take care of preventing that kind of technology from ever getting into our hands. If we ever see quantum computers in commercial hardware, it will be in very specialized devices that do tasks that 95% of civilization doesn't care about.
Great for PDA's? (Score:2)
Re:Programming Quantum Computers (Score:2)
Anyone who went to the Perl conference and saw Damian Conway speak about this will appreciate the phrase "IN CONSTANT TIME!"...
Re:Key cracking (Score:1)
Re:"Axiom"?! (Score:1)
Re:Can you imagine... (Score:1)
They could do billions simultaneously, but still take a week (or more) to do it. E.g. if you can walk and chew gum simultaneously, doesn't mean you are walking or chewing any faster.
Re:Great for PDA's? (Score:1)
But how do you propose we program a quantum device to do everyday tasks? Do think it's as simple as writing some C code? No way in hell. Go read the literature.
I'll need a new hobby... (Score:1)
-ct
Re:Can you imagine... (Score:2)
Anyone know the fundamentals of quantum computing? (Score:1)
How is it possible for a quantum computer to do this, but not a conventional one?
Re:Don't Hold Your Breath (Score:1)
So yeah, it might take sometime for the research, but I would say it would only take a few years after that(assuming Intel/AMD/whoever is in control of chips at the time decides to) before fabs spring up to mass produce these chips.
Applications? (Score:2)
I guess that my big question is this: Are these huge benefits only available in these areas, or could this be used to create a faster general purpose machine?
I know that algorithmic research for these machines is very different than standard CS. Is it just that we've only found good quantum algorithms for these applications? Or is it just that the quantum properties lend themselves to incredible speedups for these specific problems?
I don't know if anyone here can answer these questions, but I'm sure that some of you know more than I do about it! :)
Question (Score:1)
help (Score:1)
Re:Key cracking (Score:1)
The significance of Quantum Computers in the field of Cryptoanalysis is that they work differently! For a "normal" computer the time taken to decrypt a PGP messages increases rapidly with the length of the message (was it exponentially?). So a 4000 bit key will not take 4 times as long to decrypt as a 1000 bit key, but many many times as long!
The Quantum Computer built by IBM however, does it in 1 (ONE!!!) step. So if they can scale it to several thousand atoms, your 4000 bit key is worth nothing... because it will still only take ONE step!!! The only thing they need is a computer with a register long enough to hold your key (4096 bit, possibly they need a bit more..). I imagine however, that this will be quite difficult and that our keys should be safe for the near future :)
If you wonder how PGP relates to finding the period of a function (which is what IBM found) have a look at this [qubit.org]. I don't understand all the maths... but it seems someone has shown that finding the period of a function can be used to determine the factors of a large number, precisely the problem you face when trying to decrypt PGP!
Re:Predictions (Score:3)
No, wait, that's a Compaq Armada...
Umm...no (Score:1)
1) There have been MULTIPLE critical Windows updates in the past 6 months...one off the top of my head is the "Outlook Sercurity Fix" that was supposed to do away with the ILOVEYOU virus that happend recently...
2) Just because there are no updates does not mean there are not any problems...what kind of logic is that? It also doesn't mean things are improving. You can't tell me there are no problems with Windows.
3) While I was busy imagining how long it would be before a *stable* version of Linux came out for it, I thought..."Hey...how long has it been since A *stable* version of Windows came out PERIOD???"
I would argue more but my computer is about to crash and needs to be rebooted...
Linux Port (Score:1)
Re:Anyone know the fundamentals of quantum computi (Score:2)
Here's a good starting point for the non-physicist:
Quantum Computation: A Tutorial [bangor.ac.uk]
It'll won't be anything like what we're doing now (Score:1)
Unfortunately, since the task of creating workable and useful algorithms for quantum computers is still in its infancy, I very much doubt present day programmers will ever be able to sit in front on one and hack away at a piece of code. Quantum algorithms are very different from those we use in current computers.
See QUIC [caltech.edu] at CalTech or the Centre for Quantum Computation [qubit.org] at Oxford for more information on quantum algorithms.
Los Alamos has a 7qubit... (Score:4)
This article is an easy read with a GREAT summary of the history, applications, and iswsues in quantum computing: http://www.techreview.com/articles/may00/waldrop.
Re:Nice stuff they've got, but... (Score:1)
Moore and the gang of 8 at Fairchild. (Score:1)
Gordon Moore from the interview:
Anyhow, while we were making these first mesa transistors, completing development of the process and putting them into production, we had a person whose background was as a theoretician, as part of the original group, by the name of John Hoerni. And particularly when we setting up the initial equipment, John was writing in his notebook and coming up with ideas of things to try, and he came up with a proposal... of instead of making a 'mesa,' which exposes the sensitive area of the transistor to the outside world, that one should just do more of these diffusions--oxide mask diffusions--and leave the oxide over the top of the junction, the sensitive part. Well, that was something that previously had been considered a bad idea because Bell Labs' conventional wisdom was that the oxide was dirty and you wanted to get rid of it.
But we couldn't try John's idea right away because it took four index masking operations in order to make the structure he was proposing and Bob Noyce only bought three lenses!
[Laughter.]
Re:Why would we EVER see them on shelves? (Score:1)
Then why isn't it being developed by the government? Why IBM?
More Info (Score:4)
For quite some time, it was just a mind game. That was until real algorithms were discovered/invented to take advantage of these curiosities. With powerfully fast algorithms for factoring large integers (the source of encryption's security), searching, etc. they stand poised to change the face of computing. Imagine things such as cracking 1024-bit encyrtption or searching the entire phone-book in one operation.
Of course, the tricky part is to build one. Since they rely on quantum properties, they are easily bumped into a real state. But this is the source of their power too. If one particle can be in two states, then a string of particles can represent every n-bit binary number combination possible!
There are several different ways to go about quantum computing. Some use lasers to cool individual atoms to an energy-level where theyt can be controlled reliably. Others use the bulk-effect of quantum states dtected with nuclear magnetic resonance (ironaically, the caffeine molecule prooves to be particulary useful in this setup).
As of yet, they've been able to do some pretty simple arithmetic with only a few bits of information.
As for how it will change computing and programming, the best guess I've heard is that there might be quantum coprocessors someday (much like the old math-coprocessors). You see, quantum computers are thus far very good at certain kind of operations and not so good at others. This is very similar to traditional CPUs (which suck at factoring numbers in a reasonable amount of time). The two compliment each other.
I knew that information I gleaned while writing that college paper on Quantum Computing would come in handy!
On a similar note, Quantum Encryption is a related field where quantum-entanglement is used to transmit information securely. If someone were to try and eaves-drop on the system the system would collapse into a real state and the information would not be intercepted.
It'll make Crypto obsolete (Score:2)
This means, longer keys, and eventually quantum computing to enable OTPs (One-Time Pads -- yes, with Quantum computing they're possible, and, better yet, functional!)
Moores law (Score:1)
More Informative Articles (Score:1)
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Re:Key cracking (Score:2)
It is based on a concept called Quantum Entanglement. It has been shown that twin photons shot opposite directions down a fiber will, when forced to decide their state, choose the same state at the exact same time. Couple your information to this and you get crypto that cannot be broken because its "key" becomes unusable if grabbed by a third party-the photon is forced to decide state out of synch and kills the message.
Research and Development Baby! (Score:2)
Not a procedural computer (Score:1)
I heard a talk on this about six months ago (when the largest quantum computer was a whopping two bits) and I think it should be made more clear that this type of computer does not do procedural computations (it'd have to be reset every time if I understood right) -- its main application would be mathematical algorithms. The example I was given was in prime-factoring numbers (which is where all of the cryptography comes in), and as far as I know, this is the only use anyone has invented for such a computer.
Re:"Axiom"?! (Score:1)
Re:"Axiom"?! (Score:1)
Quite so, and it was originally something that Mr. Moore (I forget his first name) said sort of in passing during an interview.
Turns out he was rather insightful (hey, too bad we didn't have Slashdot back then, his karma would have ruled! :), but my understanding is he was just making an off-the-cuff remark that has been accepted as gospel by all the 'tech pundits' out there.
Cheers......
Re:Why would we EVER see them on shelves? (Score:1)
BTW, you say not for games, but why not? What, because its enjoyable means it doesn't deserve high tech?
-={(Astynax)}=-
Re:It'll make Crypto obsolete (Score:1)
Re:Hmm..... Quantum Computing... (Score:1)
The same is true for software, especially the various OS's application software runs on. There will always be bugs to fix -- you can't write 14 million lines of code without a bug (Windows 9X is about 14 million LOC I believe) -- the odds against it are just too remote to consider. And fixing some bugs will invariably cause a few more. Factor in new software with new features, new hardware components with their own problems, the device drivers for that hardware, and you begin to see the problem.
A system can't remain stable for long unless it lives in a vacuum. Computers, Operating Systems, Application Software -- none of these exist in a vacuum. Change is inevitable, and "the Problem" of keeping these things in relative harmony will thus always be with us.
So, if you can accept that any OS will always have to change, improve, adapt, etc., the question remains as to "which is better." Right now, Linux/Unix/***BSD/Whatever open source will remain a better technical solution -- more people looking at the problem means a higher chance of solving it. Closed souce solutions like WinBlows can't hope to keep up in an incremental fashion. They've done ok so far by enjoying and taking advantage of better hardware/driver support and a better application suite (in most respects), and of course better marketing and a lower learning curve. But, if they lose that advantage, they'll be through. If Office 2000 was available on Linux, there's no reason half the desktops in the US couldn't run Linux instead, almost immediately. The receptionist and the HR staff don't care what OS Word runs on, as long as it's reasonably predicatable and stable and fast.
I'd keep ranting, but lunch beckons...
Xentax
Re:Once again Perl way out front (Score:1)
quote (Score:2)
I really appreciate to see that, though quantum computers could help solving problems, they don't denigrate what came before this.
This will change from "fashion-effects" that make people forget what was sufficient until something new appeared. For example, look at how quick people got rid of the command line when the first GUIs appeared.
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Re:Hmm..... Quantum Computing... (Score:1)
Re:Why would we EVER see them on shelves? (Score:1)
Not to mention that IBM, as a technology entity, has interests in pure research, just like most other huge companies. Despite what you might think, large companies often have humanitarian and scientific interests that are not bound by capitalistic fantasies.
The example cited in the article about faster web-searching might become reality, then again, it might not. It's still only a single application, and if the time-to-fruition really is along the lines of 20 years as the quantum computing community believes, we'd be idiots to assume that the web will look anything like it does today, or even exist at all, by then. Speculating on how to apply developing technologies to the internet in 20 years is like a person in the 1940's speculating how to apply new propellor designs to new planes in the 1960's, which ended up using air-breathing jet engines instead of inefficient propellors. Except that the internet is changing a hell of a lot faster than that. It's pointless to waste time speculating about the internet in 20 years.
Re:Not a procedural computer (Score:1)
IF (spin_up) AND !(spin_up) THEN
into anything useful...
Re:Predictions (Score:1)
Re:Why would we EVER see them on shelves? (Score:2)
I want to calculate solar radiation flux! I want to simulate nuclear detonations!
Why the hell wouldn't you!!?! Video games man!
ID Software are you listening?
Quake7 - The End is Here Real world destruction in real time. You cerbal cord will twitch at the realism and your well ajusted mind will melt in trying to determine what is real, and what is just the video game. (Requires Windows XII, Ultra Linux 7I or MacOS 9.1)
Re:Programming Quantum Computers (Score:3)
Digital computing won't go away though, as the article mentions, quantum isn't good for many tasks. Most likely they'll come out with hybrid machines, a digital machine calling on the power of the quantum processor when needed. Sorta the way a gas-electric hybrid uses the better engine for a given speed. I'd think that you'd have a digital processor calling on a quantum one when the problem warrants it's power. Digital programmers'll write programs for the digital one and call the "quantum functions" via an API.
but then again I could be compleatly wrong
-ikoL
Language for quantum computers (Score:5)
A Programming Language for Quantum Computers [tuwien.ac.at]
There is also a good, comprehensive website at
OpenQubit [openqubit.org]
but it seems to be in need of a new maintainer.
My understanding is that quantum computer simulators allow one to mimic the output of a quantum computer, but without the time speed-up that real quantum hardware would provide. So algorithms can be tested out, slowly, even before powerful quantum hardware is developed. I suspect some problems can also be better expressed in a quantum computing language and would therefore be solved more easily even on classical hardware.
On the subject of simulating quantum physics on classical hardware, in the book The Feynman Processor and in Feynman's own papers it is stated that a classical computer can never perfectly simulate quantum physics. But from the evidence they give it seems merely impractical, not impossible. There can be a huge penalty in the number of steps and time required but no clear reason why a simple quantum physics system could not be perfectly simulated on a powerful classical computer. Anyone have any insight on this problem?
AlpineR
Re:It'll make Crypto obsolete (Score:2)
The problem is the tech curve. There is no way in hell that we'll have desktop end-to-end quantum crypto devices before spooks and other nefarious types get decently strong qubit computers to ravage all current encryption.
This would explain the lowering of export requirements for traditional encryption...
the classically trained are doomed (Score:5)
Why? Long explanation:
I read half of a book called Introduction to Quantum Computing (can't remember the author, but I bought it at Siggraph'99 -- there was a huge pile of this book in one booth).
Anyway, the book is great. It's almost a step-by-step guide to the math behind quantum computing while still maintaining the physical analogy. I got to the part where they discuss Feynman's method for building a quantum adder (which was merely a trivial demonstration of how to get a QM to do a classical computation).
In chapter 5 or 6, the book starts explaining how to build a Hamiltonion (QM operator function, kinda like a Laplace transfer function H(s)) for the square root of a NOT gate, I realized that anyone who's brain has been fed classical computing concepts based on Turing and Von Neuman is DOOMED to not grok this stuff (or perhaps it's becuase I'm almost 30 and my brain has turned to sand). It's kinda like trying to go from C to LISP.
So kids, that's why I recommend that you start growing the synapses now. Start growing the synapses that will help you understand this stuff before the patterns of classical computing cure in your young gray matter.
(Yeah I love how every reporter goes from: "Fascinating new qubit which is 0 and 1 simultaneously because of spin..." to "...so the qubits add all of the numbers at once to find the asnwer in one step". If you can't explain something in a 5th grade english, you don't understand it.)
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History shows the way... (Score:4)
You know that's exactly the sort of thing that the old Crays were used for. That was back in the day when "supercomputer" meant something, and these beasts only existed in ones and twos in places like Los Alamos, Sandia, and maybe Exxon.
And back then people thought the exact same things that you are saying now. "Who other than a weapons research lab could possibly use this"? The answer that surprised people is "just about everyone". The Cray-1 may be an inert piece of history now, but it's spirit lives on in our microprocessors. It's not just that modern PC's are as fast as old supercomputers, they are designed like old supercomputers.
Most innovations in computer architecture in the PC/workstation/server area have been taken from the supercomputers that came before. Surely the original researchers never dreamed that all of the complicated methods they were inventing to speed up supercomputers would wind up running some kid's game -- but they have.
Modern systems are blazingly fast, yet people continually feel the need to upgrade. In the PC biz, this seems to be driven by games and MS-bloat. Whatever the case, technology marches on, and people are willing to pay for more power. If you have the transistor budget, why not build a supercomputer on a chip? There's a market for it.
My point (such as it is) is that the hunger for performance shows no sign of stopping. It may seem ridiculous to us that an average person could ever use this much computing power. But bear in mind, that this won't even hit supercomputers for ~20 years. Think what people ~20 years ago would think about the kind of computing power that we use for games today. They would be stunned.
A little historical perspective, that's all...
--Lenny
Quantum cryptography beats quantum cryptanalysis (Score:3)
True, it's easier to break traditional prime-number based ciphers with quantum machines, but there is an effectively unbreakable cipher which can be built off a quantum computer - one that relies off the position of the atoms used as they fly through refractors that "trap" the states, and a system that relies on public-key ideas to keep that atom key a secret.
They cite quantum money as a potential example (an idea developed in the 1970s). There are some truly mindblowing consequences to an unbreakable cipher.
Re:5 Atoms? (Score:5)
"NOBODY MOVE!!!!!"
Bob.
Check C|Net Tomorrow (Score:2)
Amazing! (Score:2)
You're predicting we'll be able to see 5 atoms on a shelf in 20 years?!
Cool! That's a bigger story than the quantum computer!
Re:Not a procedural computer (Score:2)
This may seem incredibly short-sighted, but what's then to stop us from putting a quantum-computer-on-a-card inside of a traditional computer to handle those sort of problems?
Re:Key cracking (Score:2)
The Quantum Computer built by IBM however, does it in 1 (ONE!!!) step. So if they can scale it to several thousand atoms, your 4000 bit key is worth nothing... because it will still only take ONE step!!! The only thing they need is a computer with a register long enough to hold your key (4096 bit, possibly they need a bit more..). I imagine however, that this will be quite difficult and that our keys should be safe for the near future :)
The question, as you mention, is whether is is practical to set up a 4000-qbit computer such that the quantum entanglements of the 4000 qbits cause the right solution (e.g. the factors of a specific 4000-bit number) to pop out of the collapsed state. The slow crawl from 2 qbits to 5 qbits to 7 qbits suggests to me that it might turn out that the difficulty of setting up a 4000-qbit computer for a given problem isn't much less than the difficulty of just solving the problem algorithmically.
/.
Re:5 Atoms? (Score:2)
"Bill, I want to talk to you about this 20 million dollar hardware acquisition charge. All we got was this box with foam kernels in it"
"You opened the box?! You fool! You let all the quantum computers out! Now I'll have to reorder them! The board will hear about this!"
Later
Erik Z
Programming Quantum Computers? (Score:2)
I have to admit first off here that I haven't read up as much as I should about quantum computing. Nontheless, I find myself wondering: what will it be like writing software for a quantum computer? Will quantum machines even be stored-program computers?
Could it pass the Turing Test? (Score:2)
Re:Key cracking (Score:2)
You don't seem to get it. A quantum computer in effect "knows" the answer right at the beginning and it just takes a little bit of time to display it. If quantum computers were to ever become stable enough to have the ability to run something like linux at the speed of a Pentium, your 40960 bit long key would be rendered useless in minutes if not seconds.
A very simplistic way to look at it is you have a room with n switches, where n is the number of bits in you encryption, and some lights connected to those switches. In order to have all of the lights on you need to have those switches in a specific order. A regular computer flips the first switch, turns around and checks to see if the lights are on, if not moves on in a binary fassion (there are better ways of doing it but this is just a simplification). It will go through all of the combinations until it hits the correct answer. A quantum computer has the equivelent to a cheat sheet with the answer on it already and it only takes enough time to flip the switches in the correct order.
Standard cryptography today is useless against quantum factorization. Luckly, right now there is no way to keep the particles in a stable configuration. If you think that large bit encryption will keep you safe from quantum computers, when they finally become viable, then you are asking for you messages to be broken.
Re:Why would we EVER see them on shelves? (Score:3)
Whew! I'm glad you figured it all out for us. You saved everyone a lot of time and money by letting us know what what we shouldn't be doing with quantum computing.
Oh, but I think you're wrong on games, I believe you'd be able to program some incredible AI for games like Quake, Or do fantastic universe simulations for games like Elite or privateer.
You're right about the spreadsheets though, who needs spreadsheets when you have have a quantum computer go though all the possible combinations of funding for a company to come up with the best fiscal plan, in about two seconds.
And I'd hate to have one of these things on my desktop, I mean, I'd be playing with it all the time, trying to find out new things that could be done with it. Working together with other cutting edge geeks out there...I mean, what's the point?
Sheesh,
Erik Z
Re:Key cracking (Score:2)
Re:Programming Quantum Computers (Score:3)
P=NP (Score:2)
Right now my solution:
P=NP where N=1 just doesn't seem to work...
Crypto has many uses (Score:2)
Burris
Re:Language for quantum computers (Score:2)
These opinions are my own and not necessarily
Re:Why would we EVER see them on shelves? (Score:2)
Yeah, right. I remember when the Compaq Deskpro 386 came out. "That'll make a great server, but nobody really needs a workstation that fast." So naive. In 20 years, the a.out from hello.c will be 50 megabytes, and you'll need something with a the power to simulate a nuclear explosion just so that MS Word will be able to keep up with your typing speed.
I know. You think I'm joking, or that I'm wrong. But I'm not. Try MS Word 2000 on a Pentium 66 some time and see if it can keep up with your fingers. In 1990, you would have laughed at the idea that computers were going to be slower in 1995 than they were in 1985, but guess what? It happened. Ain't software "progress" great?
20 years from now you're going to be begging on your knees for one of these quantum computers just so you can read your email without falling asleep while waiting for the screen to redraw. And in 2023 your "old" quantum computer will be totally obsolete.
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Re:Why normal computers can't simulate quantum one (Score:2)
This part of the book is very "mathematical" and its conclusions must be regarded as true.
Actually, many reseachers, in both physics and AI, do not regard it is true. And the question of "intelligent computers" is still an open one.
Just because something is mathematical doesn't make it true. It may follow from the assumptions, but it is Penrose's assumptions that are in dispute.
See Dennet's Consciousness Explained for an example of a viewpoint opposed to Penrose's.
Steve M
NMR is dead end for QC (Score:2)
That's fine, as long as 10^23 votes is enough to overwhelm any errors. But for a serious number of qubits, the unavoidable chance of quantum bitflip in each atom means that eventually less than one of those 10^23 molecules is in the correct starting state. Perhaps you can solve this by quantum error correction - the algorithms aren't worked out yet - but that multiplies the number of bits needed for a given problem by a factor of (provably) 2 or (probably) 3. Then you have the problem that any operation can only involve closely neighboring bits; to add register A to register C requires huge numbers of operations to shuffle with register B. Finally, to read or write to any given bit, you need a unique frequency to address that bit. With hundreds of bits, only a few can possibly have frequencies that stand out enough. These problems, combined, add one or more factors of N to the resources necessary; it's still polynomial, but...
Quantum dots - single particles, NOT entire atoms, confined electrically to a single quantum state - are more hopeful. Because they can be physically rearranged or put in more complex configurations and still physically addressed on an individual basis, the problems above go away or become more manageable.
Re:Key cracking (Score:2)
Don't brush quantum computing aside because it will come to nip you in the butt before you know it.