Author: dabacon

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!

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.

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.)