One of the big pushes occuring in ion trap quantum computing these days is the construction of different ion traps which will be useful in scaling up these quantum computer architectures. Chris Monroe’s group at Michigan (in collaboration with Keith Schwab at the PRL in Maryland) has a nice paper out a few days ago in Nature Physics describing a new ion trap they have built (for a news release, see here. ) This microtrap is built, basically, on a semiconductor chip, and is of the micrometer size as compared to the millimeter sized traps normally used for trapping ions. Because these traps are fabricated using semiconductor MEMS technology, it is not unreasonable to think of building traps which can stored hundreds to thousands of ions at a time.
One interesting property of the traps described in the paper is the shallow depth of the trapping potential as compared to the depth of the potential for larger, milimeter scale traps (about 0.08 eV in the former compared to order 1 eV in the latter.) What this means is that the ions they trap stay in the trap for minutes as opposed to days, and that it has not been possible to simultaneously trap two ions in the trap. Which is what I love about experiments: while this is an important step, we’re certain to see more steps in the future and it is not unreasonable to expect some good scaling up in of ion trap quantum computers in the next few years.
Another set of experiments involving traps designed to be scalable comes from Isaac Chuang’s group at MIT. A preprint of their work is available as quant-ph/0511018. Me, I just like to flip to the end of their paper and stare at their neat hexagonal trap and dream of the cool things I could do with such a trap.
Physicists and Computer Scientists
Scott Aaronson and Lance Fortnow discuss What should physicists know about computational complexity?
I’m thinking that this deserves a rejoiner, “What should a computer scientist know about computational complexity?” I mean, how silly have these computer scientists been…they’ve been studying classical computers for all these years, when it is totally obvious (at least to a physicist like me) that they should have been studying quantum computers. 😉
This reminds me of my favorite way to distinguish between a computer scientist and a physicist at quantum computing conference. Physicists are the ones who think that NP stands for “not polynomial” and computer scientists are the ones who think that a Hamiltonian is some sort of sandwich.
QIP 2006 Talks
QIP 2006, to be held in Paris, now has the list of talks for this workshop here. There were 160 submissions! There are eight invited talks, sixteen long talks, and sixteen short talks. Lots of interesting talks, which makes me wish I could have figured a way to attend (that and I’ve never spent any time in Paris.)
By the way, for those of you thinking of applying to graduate school in quantum information science theory, this list of speakers, and the institutions they represent, would probably be a good place to start.
Last Trip
Last trip of the term visiting the Institute for Quantum Information at Caltech this week, my old stomping ground (for seven years!) Those who are bored might be interested in the talk I’m giving tomorrow for the IQI seminar. It is possible that after this talk you might even be more bored, but, well thats a chance you’ll have to take. The title of the talk is “Wasing Away in Hidden Subgroup Ville.” Yeah, I’m still looking for that lost shaker of salt.
CSE 599 – Quantum Computing
The course I’m teaching next term:
CSE 599 (Special Topics in Computer Science)
Quantum Computing
—————————
Instructor: Dave Bacon
Time: Monday and Friday, 1:30-2:50, Wednesday 1:00-2:20
Location: CSE 503
What are the ultimate limits to the information processing power of computing machines? Since computers are physical devices, it makes sense to look for the answer to this question through the lens of our theories of physics. Astoundingly it was discovered over a decade ago that there exists a completely different kind of a computer than today’s modern computer. This new type of computer has the peculiar feature that it processes information according to the laws of quantum physics. Remarkably, such quantum computers have been shown to possess superior computing power over today’s classical computers. For example, in 1994 Peter Shor showed that a quantum computer could efficiently factor whole numbers (a task for which there is no known efficient classical algorithm.) This discovery is especially important since it tells us that if we build a large scale quantum computer, the most widely used public key cryptosystems will no longer be secure.
This course will serve as an introduction to the theory of quantum information science. Today this field is too large to cover in one course, but we will cover two of the most exciting fields in quantum computing: quantum algorithms and quantum error correction. No prior knowledge of quantum theory is necessary for this course, but prior exposure to linear algebra will be assumed.
The course will run three days a week from Wednesday January 4, to Friday February 17. Questions about the course can be directed to Dave Bacon at dabacon[aaattt]cs.washington.edu .
The course has a number which makes it sound like it is for sale, 599.
Jobs in Quantum Information Science
This is the first year in a few that I haven’t been applying for jobs (You might suspect that this makes me less grumpy. Well, judge for yourself!) Now I could be wrong, but is this the first explicit advertisement by a U.S. university physics department for a theory position in quantum information science?
Quantum Information Theory
The Department of Physics and Astronomy at the University of Southern California invites applications for tenure or tenure track positions at all faculty levels in the area of Quantum Information Theory.
Well even if it isn’t the first, can we take this as a good sign?
Ski Season 05-06, Day 2
Saturday I went to Steven’s Pass for a day of skiing. This ski area is rather nice, especially due to the fact that they had about a foot of new snow. I suspect, however, that when the snow conditions are icy the place isn’t as much fun. What was amazing about the ski area was the number of people on the runs in comparison to the waits at the bottom of the lift. There were tons of people on the runs, but very small lift lines (at least on the backside.) Also if you go to Steven’s on a weekday, you should go early. Why? Because the wait to buy a ticket was absolutely ridicious. I mean, I have never seen lift lines move so slowly. Oh, and by the way, my new skis rock!
Ion Trap Quantum Computer Papers
Interesting papers in experimental ion trap quantum computation:
Creation of a six-atom ‘Schrödinger cat’ state from Wineland’s group at NIST Boulder, Nature 438, 639-642 (1 December 2005.) Schrodinger’s cat is now six qubits big! And growing! What a cute little kitten.
Scalable multiparticle entanglement of trapped ions from Blatt’s group in Innsbruck. Nature 438, 643-646 (1 December 2005.) In this paper the group discusses experiment they performed which created the so-called “W” entangled state for up to eight qubits. That’s a quantum byte, peoples! Amazingly the group performs full state tomography on these states. Wow that sounds like an awful lot of graduate student hours.
3.14159265…
Steve sends along this link to…well, it’s a bit hard to describe, but it involves pi. No, not pie, pi!
More Dice
The full t’ ‘t Hooft (look I put the apostrophy in the correct location!) article is now posted at Physics World (not Physics Today, as I listed incorrectly in my first post) commentary by Edward Witten, Fay Dowker, and Paul Davies. Quick summary: Witten thinks that quantum cosmology is perplexing, Dowker worries about the emergence of classical physics, and Davies postulates that complexity is the key to understanding the emergence of classicality. Davies suggests that quantum mechanics will break down when the Hilbert space is of size 10^120 and suggests that quantum comptuers will fail at this size. His argument could equally be applied to probablistic classical computers, and so I suggest that if he is right, then classical computers using randomness cannot be any larger than 400 bits.