Rod Van Meter makes the prediction that the first production quantum computer will cost forty bucks a qubit. He arrives at this number by assuming the first application will be factoring a 1,024 bit number which requires about five kilobits (kiloqubits?) and adds in a factor of fifty for quantum error correction. Thus there is a total of one quarter of a million qubits and figures such a machine could cost around ten million for the figure of forty bucks a qubit. It’s interesting to reason about this by first setting the cost instead of by estimating the actual costs. Why I like this approach is that if we suppose that a similar quantum computer costs ten times as much, then we simply won’t be building such a computer. Of course, I’m not sure how much the NSA would pay for a quantum computer: it may indeed be in the hundred million dollar range if factors 1,024 bit numbers.
Of course, I don’t believe in quantum error correction…or rather I don’t believe we will use the standard approach to quantum error correcting to obtain a fault-tolerant quantum computer 😉 . Thus I’m betting the first quantum computer will cost around a dollar a qubit (although I certainly think some of these “qubits” may in fact be made up of hundreds to thousands to millions to 10^19 number of single quantum systems.)
It will be interesting to see how far off Rod and I are at date Q. I suspect Rod will be closer mostly because he’s actually worked in the real world.
Update: For comparison the ENIAC cost about half a million dollars in 1945 which is about five million dollars in today’s money. The total number of vacuum tubes in that monster was around 20,000. Thats 500 of today’s dolars per vacuum tube. And, of course, today, I can buy a computer with 50 million more than a billion transistors for under five hundred bucks!
Constructors, Automata, and Evolution, Oh My!
Find of the day: an online version of John von Neumann’s “Theory of Self-Reproducing Automata.”
Nature Physics Versus PRL
On returning home from Boston (one and a half days late due to 1. a broken plane and 2. a missed connection in Dulles), I found I had received my first copy of Nature Physics. I must say, I was very impressed by the first issue. Why? Well first of all are the gorgeous color pictures. Everyone loves color pictures, right? Seeing a journal of well written, beautifully typeset and illustrated physics articles appeals to the right side of my brain (the part that hasn’t shriveled away from too much math 😉 ) Second was that, unlike PRL, of which there is absolutely no way one can read all of the articles in a single issue, Nature Physics has a reasonable number of well written articles (at least for this initial issue.) I see from their author submission page that letters are limited to 1500 words long (typically four pages long) and articles to 3000 words long, which is a bit more freedom than that afforded by Physical Review Letters. I suspect that Nature Physics will quickly become a prestigious place to publish ones work. Of course, in an idealized world, it wouldn’t matter where you publish your work, as long as it was excellent work. On the other hand, it is true that due to the selectivity of different journals I’m more likely to find excellent work in certain journals than in others.
Quantum Audio Upgrade
Via a student from the class I taught this last summer, The Intelligent Chip:
The Intelligent Chip is a one inch square, bright orange plastic wafer that, when placed on top of a compact disc player for 2-3 seconds, upgrades the disc (CD, DVD or SACD) being played at the time. The sound of the upgraded disc has more detail and articulation, better dynamics and an absence of “digital harshness.” Voices are more human-sounding and less synthetic. The upgrade is permanent. Inside the white translucent Intelligent Chip case are two ultrathin, clear polycarbonate sheets, one on each side of the Chip. The manufacturer’s product brochure states, “The Intelligent Chip should be put back into the packing case after using, because the packing case can protect the quantum material of the Intelligent Chip, preventing them from leaking.”
Read the description of how it works. Who says quantum information science isn’t going to revolutionize the world….of audio devices. Why does my mouth taste like snake oil?
Computation….On the Edge
Via Three Quark’s Daily (Update: and also at Geomblog, which I somehow missed reading, but which has some great comments about quantum information science): The Edge (which you either love or hate) has announced a $100,000 prize in computation science The list of nominations for the first prize was announced at Festival della Scienza in Genoa on Novermber 1st.
The list of those nominated is a pretty interesting. From quantum computing land, those nominated are
CHARLES H. BENNETT, for his many ongoing contributions to the physics of information, including reversible computation, quantum cryptography, quantum teleportation, and quantum communication theory.
DAVID DEUTSCH, for the enormous potential of quantum computing in studying the architecture of the brain.
SETH LLOYD, for turning quantum computers from dream into device.
PETER SHOR, for his discovery of revolutionary algorithms for quantum computation, which will hasten the day when this fundamentally new mode of computation becomes practicable.
That nomination for David Deutsch seems a bit strange to me: it sounds like it was written for Roger Penrose! I would have nominated David Deutsch for fundamental work developing the idea of a quantum computer, realizing that quantum computers could outperform classical computers, and for fundamental insights connecting physics to the foundations of computer science.
Let It Snow, Let It Snow
Sweet, sweet, NW weather news. But remember, even with this good news, it is important for everyone to continue to perform a snow dance every few days or so.
Superpositions of Worms Going In and Out
Over at Fact and Fiction there is an interesting post about an article in New Scientist called Attack of the Quantum Worms.
Having not read the article, I thought I’d be an idiot and comment on what one could possibly mean by the statement that quantum computers are more susceptible to malicious attacks. I’m an even bigger idiot because I know very little about computer software security. But life’s about saying silly things and then getting chewed out by all you smart people, know?
The first thing one might mean is that quantum data cannot be backed up due to the no cloning theorem. OK, suppose I’m a hacker who wants to attack your quantum computer. Surely if I write some code which is executed by the computer and it damages the quantum state of the system, then, because I can’t back up the state of the quantum computer, I’m in big trouble. So it seems that one cannot prevent crashing a quantum computation by backing the state of the system up. But this isn’t quite right, is it? I mean suppose we have a classical computation and we make two backups of the state of the computation at any time. Then we can use this to test whether one of these states has been corrupted by majority voting. But we’ve learned that we can do exactly the same thing for quantum computers: we can detect if the quantum state of one of our copies has been corrupted by encoding into a quantum computer. Now we need to use more than three qubits per bit, but still, this doesn’t seem like such a big deal (from a theorist perspective 😉 ) Now I’d also like to say that I don’t think this is even the way classical computers protect themselves versus malicious software.
So what about attacking the “quantum software?” Well in a standard circuit model of quantum computation, the software is just a list of classical expressions. There is nothing quantum about the data describing a quantum computing program. So it seems that there can’t be any difference here between the quantum and classical world.
Oh well, I really should get a copy of the New Scientist and figure out if any of this rambling has anything to do with the article (on a similar note, I don’t understand the second part of the post at Fact and Fiction. I just don’t see the relevance of copying in a fixed basis: this is something which we almost always avoid in quantum computing because it destroys the coherence properties of the subsystem being so copied.)
Boo!
Happy Halloween!
Posting has been low because I’ve been visiting Isaac Chuang at MIT. There seems to be a very popular costume here at MIT for Halloween: everyone is dressed up as a science geek 😉
Signaling and Information
One basic concept which has emerged in classical physics (and then moved on to the quantum world) is that it doesn’t appear possible to send information faster than the speed of light. What I find fascinating about this is that it seems to be, like Landaur’s principle, a statement which connects physics (special relativity, local field theory, quantum field theory, etc.) with, essentially, information theory (the concept of a signal, the concept of information capacity).
But now suppose, as I have argued before, that what makes a physical system a “storage” device is very much a matter of the physics of the device. Thus, for instance, I could try to encode information into the position of a particle on a line. Is this a good way to encode information? Well, certainly we could try to do this, but in the real world it will be very hard to achieve many orders of magnitude precision on this measurement because the system will interact with the rest of the world. While isolated we can talk about such an encoding, but as we crank up the real world meter, we find that there are limits on this encoding. Or to put it another way, the ability of the system to store information is a function of how it interacts with the rest of the world, a function of the physics of the system.
And if the ability of a system to store information is a function of the physics of the system, why isn’t the no-faster-than-light rule, a rule which is essentially about information transmission in physical systems, also a function of the physics of the system?
Performance Enhanced Theorems
Among sports fans there is a lot of controversy about the use of performance enhancing drugs by athletes. Of course what exactly an performance enhancing drug is, is often left pretty vague. But most sports fans argue against the use of such drugs because they are, in some form, cheating.
So what do we do, for example, with Erdos. Paul Erdos was, for those who don’t know, one of the twentieth centuries great mathematicians. He was the author, amazingly, of over 1,500 different papers. It was well known, also, that Erdos used amphetamines. There is a famous story that his friends were so worried about his amphetamine use that they bet him that he couldn’t stay off the drugs for a month. Of course Erdos took the bet and successfully stayed off the drugs for the required amount of time. When he went to collect the bet, he reportedly said “You set Mathematics back one month!” (OK, this story is off the top of my head, the details may or may not be correct!) So, in a real sense, Erdos’ productivity was increased in large part by his use of a performance enhancing drug. So, was Erdos cheating? Should we think of his “records” his “theorems” as somehow being “less proved by Erdos” because of his use of amphetamines? Well I certainly would argue against this.
At FOCS this year I was having this conversation, and it came up that perhaps we shouldn’t penalize the result, because the outcome, i.e. the mathematical proofs isn’t really a competitive sport. But what about those who are competing for tenure? Now of course I’m disregarding the legality of the performance enhancing drugs. But disregarding this issue (which may just invalidate the whole argument, but bear with me) should there be drug testing of tenure track professors to make sure they aren’t using amphetamines to increase their productivity?