Ah, the Life of a Theorist

Nothing quite like staring out at the beautiful mountains of Innsbruck while Scott Optimizes and I Pontifficate.
Thinking In Innsbruck
Dave: “Gee I wonder what the meaning of life is?”
More Thinking In Innsbruck
Scott: “That’s not a very precise question. Could you please state some conjecture about the meaning of life that I can prove?”
Even More Thinking In Innsbruck
Dave: “Let x be a postive integer….”
[Thanks to Hans Briegel for these amusing pictures.]

Quanteninformation

Now this
Innsbruck Office View
is what the view from every office should look like. I’m currently in Innsbruck, Austria visiting the Institut fur Quantenoptik und Quanteninformation. One of the few place in the world where you can study quantum computing and then go skiing. Or if you want to, you can go skiing and then study quantum computing. Of course my favorite is to ski and do quantum computing at the same time. This is fine just as long as you realize that putting yourself in a superposition of going to the left of a tree and to the right of a tree will most probably result in you dying.
Scott is here as well and tomorrow the poor denizens will get a double feature of our talks.

On the Road Again

Last week I was in Boulder for a workshop on ion trap quantum computing. Basically nearly everyone who is working on ion trap architectures for quantum computing was there, which was pretty incredible. A highlight of the workshop, besides the excellent experimental results, was that I got to see one of the participants describe how the ions will be shuttled around using his feet and then turning this description into a dance step. The ion trap boogie, or something like that. Won’t it be great to see the actual boogie in the ion traps?

SQuInTing at Pirates

This last weekend I attended two out of three days of the SQuInT conference in Albuquerque, NM. The conference, as usual, was stellar, and was rather large this year, with nearly 150 people! The only real draw back this year was that the hotel the conference was in had variously scheduled (1) a band, and (2) a group that liked to sing and cheer in the room adjacent to where the conference talks were held. When the crowd next door broke out into a hymn I almost lost it. Almost.
Anyway there were a lot of very interesting talks at the conference (schedule can be found here.) But I must say there was also the most unusual talk I have seen in a long time. And I must say it was also one of the best talks I have seen in ages. It was given by Jonathan Walgate from the University of Calgary. Here is the title and abstract:

Quantum Buried Treasure
Jonathan Walgate (University of Calgary)
Abstract. A swashbuckling tale of greed, deception, and quantum data hiding on the high seas. When we hide or encrypt information, it’s probably because that information is valuable. I present a novel approach to quantum data hiding based on this assumption. An entangled treasure map marks the spot where a hoard of doubloons is buried, but the sailors sharing this map want all the treasure for themselves! How should they study their map using local operations and classical communication? This simple scenario yields a surprisingly rich and counterintuitive game theoretic structure. A maximally entangled map performs no better than a separable one, leaving the treasure completely exposed. But non-maximally entangled maps can hide the information almost perfectly! Quantum data hiding was developed with two motivations. It is worth investigating purely as cryptographic scheme, allowing data to be concealed from cryptanalysts sharing a perfect copy. However it also provides an operational framework for studying entanglement and nonlocality, as it hinges on the difference between local and global physical information. `Quantum buried treasure’ schemes have four key advantages. Firstly, the local perspectives of those sharing the quantum system are clearly revealed, and this allows a more detailed comparison between the local and global information. (Previous schemes have treated local observers as a single collective eavesdropper, albeit operating under local constraints.) Secondly, interesting competitive situations emerge among the local parties. These suggest a useful role for game theory in quantum mechanics that emerges naturally from its nonlocal structure, unlike artificial attempts to unify the two. Thirdly, buried treasure provides a more realistic model both of encrypted information, which tends to be actually valuable, and of the motivations of those attempting the decryption. Last but not least, Alice and Bob get to be pirates!

Argy matey. Notice especially that last point. The talk was very amusing, as you can imagine. Hopefully there will be a paper coming out soon, as the idea is fascinating and, I must say, one of the first times I’ve seen a quantum game theory paper and haven’t wanted to jump out of my seat and shout something. Well this time I only realized afterwards that I wanted to jump out of my seat, but I didn’t have a chance to ask Jonathan my question so I guess I’ll have to wait for the paper.
Another talk I found very interesting was Andrew Landahl’s work on a quantum algorithm for ordered search problems (Update: I forgot to mention this was joint work Andrew did with Andrew Childs and Pablo Parrilo.) An old result of Farhi et. al. showed that one could search an ordered list using 3 times log base 52 of the size of the database. This algorithm should, of course, be called the card players algorithm ;). If we work in base 2, this works out to an algorithm which is approximately 0.53 log base 2 of the size of the database. The best lower bound (IIRC) was 0.22 log base 2 of the size of the database. Of course, quantum computer people like square root speedups, so a natural guess is that the real answer is log base 2 of the square root of the size of the database. But Andrew was able to show, by solving some neat little semidefinite programming problems, that 4 times log base 605 the size of the database queries suffice. This is about 0.43 times the log base 2 of the size of the database, hence destroying the naive quantum computing Grover guess! Well how excited should we be about these “constant” speedups? I’m not sure. On the one hand they are not as sexy as Shor’s algorithm (what is!) but on the other hand, they are kind of cute demonstrations that if you build a quantum computer comparable to a classical computer you should pay at least a constant amount more to use the quantum computer 😉
Another talk which I need to think more about was given by Masoud Mohensi (USC/University of Toronto). Masoud talked about work he did with Daniel Lidar on what they call “Direct Characterization” of open systems quantum dynamics. The idea here is to perform process tomography without having to actually perform quantum state tomography, and in the process obtain less use of resources. In particular Masoud showed how to use entangled states as inputs into a quantum superoperator and then characterize this superoperator using 4^n Bell measurements where n is the number of qubits. Papers on this subject can be found as quant-ph/0601033 and quant-ph/0601034.
Finally, of great interest to everyone, I’m sure, I learned that the state of New Mexico is building a spaceport. That’s right, the economically depressed state of New Mexico is going to make their stamp on the world by building a spaceport! I also heard a theory about this from one of the participants at the conference. This person suggested that he now understood the UFO landing at Rosewell. Apparently the aliens simply set their time machine incorrectly and ended up a few years early! (Their maps for the spaceport were correct, but they misdialed the “YEAR” dial, most certainly due to a translation problem caused by the Babelfish.)

All My Bags Are Packed

After class today (literally) I head off on quite a journey. Albuquerque to Boulder to Seattle to Santa Barbara to Seattle to Santa Barabara to Seattle. Those Seattle waypoints? Laundry and getting my wisdom teeth pulled. Unfortunately I’ll be missing the first day of the SQuInT conference, but maybe I will be able to blog something about the conference tomorrow.
Update: I will be flying into the Albuquerque sunport, and unfortunately, not the Albuquerque spaceport which hasn’t been built yet.

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.

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 😉

The Gospel of Theoretical Computer Science

I’m in Pittsburgh this weekend for FOCS 2005. This is the first FOCS I’ve attended.
This evening there was a panel discussion at the business meeting (free beer!) on “Exciting the public about (theoretical) Computer Science.” (Update: for a detailed description of the business meeting see Rocco Servedio’s guest post at Lance Fortnow’s blog and for a real computer scientist’s comments see here and for a nice collection comments head over to Geomblog. For a fare and balanced counter, see Pit of Bable) It was very interested to hear about the severity of the public image crisis the field of theoretical computer science currently finds itself facing. It is true that even within the broader computer science community, theory is oftentimes seen as not very important. But beyond this, the public’s perception of the theory of computation is very limited and a lot of the panel discussion focused on how to fix this. I mean, if I ask random people if they know anything in theoretical computer science, what are the chances that they will know anything? At best you might be very lucky and meet someone who has heard of the P versus NP question. On the other hand, mention physics to people, and they immediately think nuclear bombs, black holes, perhaps lasers and string theory, quantum mechanics, and atoms with electrons zipping around a nucleus (well I’m not saying any of these things are correct physics 😉 ) So how can theoretical computer science convey the excitement of the field to the general public?
Concrete suggestions like “publish in Science and Nature” and “get IEEE and ACM to hire someone to do PR” were offered up, and probably deserve serious consideration. It was interesting, to me, originally(?) a physicist, to hear how physics and astronomy were held up as prime examples of doing a good job conveying to the public the excitement of their research. It is true that physics and astronomy do a good job of conveying the excitement of the field, and there are various reasons for this.
But I’d like to focus on why theoretical physics has done a good job at exciting the public. Why? Because this is much closer to the theory of computation. Because lets face it: CS theory doesn’t have things dug up from the ground (dinosaurs, early primates, archeology), nor beautiful pictures of alien environments (planetary science, all of astronomy). And theoretical physics, like CS theory is hard. I mean really hard. And also, I would claim, theoretical physicis and CS theory share a very fundamental similarity in that they are both essentially about advanced creative problem solving.
So let’s look at theoretical physics. How is the excitement of theoretical physics conveyed? Well, the first things that probably pops into most peoples minds that is related to theoretical physics are Stephen Hawking’s “A Brief History of Time” or maybe Brian Green’s “The Elegant Universe.” Or maybe the recent NOVA program on “E=mc^2.” Now clearly neither of these books or the TV show is explaining to the public the “real” story of the theoretical physics. But what they do a good job of is convincing the audience that they, the audience, actually understand what is going on. As was mentioned on the panel tonight, people will hear about gravitons and think that they actually understand the physics of gravitons. But really, of course they don’t. Do they even know why exchange of particles can give rise to attractive forces or the connection of whether these forces are attractive or repulsive to the spin of the exchanged particle. I seriously doubt it. Yet, the authors of these books and TV shows have successfully given the audience the feeling that they do understand the field.
There are stories I have been told about Richard Feynman (OK, yeah, I just can’t resist another Feynman story) which said that when you went to one of his lectures, while you were listening to the lecture you would think “Yeah! This is great! Everything makes total sense now!” But when you left the lecture and tried to recall the reasoning and what Feynman was teaching, you couldn’t reproduce the results. I maintain that what was happening here is the same thing which good popular expositions on theoretical physics do: they convince the reader that they understand what is going on even though they most certainly do not. What is funny about the Feynman stories, of course, is that these are real physicists who themselves probably should understand the subject, and yet Feynman was able to convince them they understood what was going on, even though they really didn’t. Kind of scary.
So what lesson do I draw for this for the theory of CS? Well they need a Richard Feynman and a Stephen Hawking! But seriously, they need to attempt to convey their results in a way which, while not toally faithful to the science, gives the reader a reason to believe that they understand what is going on. This, of course, is much hard to do as a computer scientist than as a theoretical physicist because in the former rigor is held in higher esteme than in physics where hand-wavy arguments hold a much greater standing. But certainly even theoretical physicists (except the best) have to distort their understandings to meet the general public. So my advice to the theoretical computer science community is to let the rigor go but convey the spirit in a way that convince the public they understand what is going on.
Now one might argue that this is dishonest. And to the brighter readers it certainly is. But remember, it’s not the bright readers which are the main concern: they don’t consitute the public (if they did I wouldn’t be writing this post nor would FOCS be having this panel discussion. Nor would their be trials about whether intelligent design should be taught in science courses at the beginning of the twenty first century.)
Another interesting perspective coming from physics is that theoretical physics has conveyed to the public that it is really pursuing something fundamental. The two big fundamentals are “learning the laws of nature” and “understanding the origin of our universe.” CS theory hasn’t, in my opinion, exploited the fact that it is studying a fundamental question: the fundamental limits of computation. This fundamental research direction, to me, is as deep as understanding what the laws of nature are (and if you catch my on some days I might even say that one is deeper than the other. Which is deeper depends on the day. And perhaps the last time I’ve had a conversation with Scott Aaronson.) Certainly this is one of the reasons people get interested in the theory of computer science. I myself have very fond memories of reading “The Turing Omnibus” which introduced me at an early age to ideas of P versus NP, error correcting codes, the von Neuman architecture, the theory of computablity, etc. This excitement is as exciting as thinking about string theory, or supersymmetry, or solutions to Einstein’s equations. And it certainly, is a fundamental question, about our universe (I began my thesis at Berkeley with the sentence “Our generous universe comes equiped with the ability to compute.” Heh. Pretty cheesy, no?)
I think I could go on about this subject ad nauseum. So I’ll stop. And, of course, I’m more of an outsider than an insider here. This is my first FOCS. On the other hand, when one of the panelists asked how many had publised in Science or Nature, I was one of about four who got to raise their hand. And the paper even had some computer science (about universal quantum computers) in it! And remember, if you publish in Nature or Science, there is the possibility of being sucked into their press cabul and there will be articles about your work appearing simultaneously around the world’s newspapers.

Singapore Airport

I just couldn’t resist free internet access at 5am in the morning in the Sinapore Airport.
Update: Nor could I resist internet access at the Tokyo airport.

Flash, Boom!

Singapore. Nothing like a thunder storm at 2 am.
I’m here to visit the Quantum Information Technology Group at the National University of Singapore, a.k.a. quantumlah. Their motto is “We do IT with qubits.” Which reminds me that I need to get my personalized Washington state license plates. In California, I had the plates “QUBITS” (because one qubit isn’t that interest). What should I get this time? I was thinking of “NTANGLD” or maybe just “QUANTUM.”