John Baez’s description of Hawking’s talk at GR17 is the best scientific commentary on the talk I’ve come across. It’s a notch above all of these descriptions I’ve read which are of the form: I don’t like Euclidean quantum gravity, but I do know [insert other theory of quantum gravity here], and we already knew [insert claim here]. Which is fine for learning about [insert claim here] but doesn’t really tell me anything about what Hawking was trying to say!
Northern New Mexico
From George Johnson’s New York Times July 3, 2004 article “Los Alamos’s Super-Secret Heritage Shows Some Cracks:”
When science is conducted in secrecy it takes on the air of magic.
From its beginnings as an outpost of the Manhattan Project, Los Alamos has operated in a state where the ideal of science as the free exchange of information has been indefinitely suspended, replaced by a conviction that there is safety in ignorance, that life is more secure when certain powerful ideas are kept among a few.
Peace through the nonproliferation of knowledge, another of the ingrained absurdities of the nuclear age.
Which reminds me of why cryptography (and quantum cryptography in particular) is so disturbing to me: does the universe really allow for the hording of information? Our unsharing universe? Of course, the type of knowledge Johnson is talking about, “scientific knowledge”, does appear to be open to everyone: you don’t get exclusive rights to the science when you discover it. But what if the universe didn’t even work that way? What if the mere discovery of some new bit of science closed the door for all others investigating the same phenomenon?
The Entropy of Lost Bets
Reading John Preskill’s description of his bet with Stephen Hawking on the black hole information paradox, I began to wonder what my requirements for thinking the paradox had been solved would be. The bet Preskill and Hawking and Thorne made was
When an initial pure quantum state undergoes gravitational collapse to form a black hole, the final state at the end of black hole evaporation will always be a pure quantum state.
Well at first I thought, surely a quantum theory of gravity which showed such a preservation of purity would be sufficient? Wouldn’t it? Well, a single quantum theory of gravity might be evidence, but even if we find that theory, what makes us think it is the correct theory describing our universe? Yeah, yeah, string theorists mutter something about “the only way.” So do Taoists.
This, I guess, is the funny thing about bets made by theorists. Their criteria for satisfying the bet may have nothing to do with reality. We may resolve the paradox, say in the Euclidean theory of quantum gravity, but what if the Euclidean theory of quantum gravity doesn’t correctly describe our universe. What if Twistor theory ends up giving a valid theory of quantum gravity and entails a total overhall of quantum theory such that the paradox is resolved in the opposite direction? What if the theory of quantum gravity makes it apparent that the question doesn’t even make sense?
The only way I’ll be happy is if we go out and create a black hole. Let it evaporate. And track the information flow. Admitting this, I believe, has just caused my theoretical physicists i.d. card to spontaneously combust. Excuse me while I put out the fire in my wallet.
Physiology of Heartache
Today I got curious about what causes the physical feeling of “heartache.” Well at first I just was curious if I could find any well written physical descriptions of heartache. While there are certainly thousands of sentimental descriptions, I couldn’t find a single description of the physiology of heartache. Further according to one article there is no known physiological explanation for the physical feeling of heartache. Strange.
On the other hand, I did learn that there may be a relationship between a broken heart and an increased chance of a heart attack (although the few studies I dug up were not totally convincing.) Our modern world: “Better to have loved and lost than to have never loved at all (unless you’ve got a history of heart disease.)”
Paper Collaboration Software
Recently, I completed a paper with Isaac Chuang and Aram Harrow. In the final stages of completing the paper we used a CVS (Concurrent Version System). For those not familiar with CVS, this is a piece of software which allows for version control (meaning it records the history of the source files) and nicely protects multiple authors working on the same source (basically this means multiple authors can work on the paper without fear of overwriting other’s changes.)
Using a CVS was definitely an improvement over the normal way paper collaboration works: the authors bounce emails back and forth with the source (aka LaTeX) attached. This essentially means that only one person at a time has “the token” and is responsible for working on the paper. While knowing that “you have the token” can press you into working efficiently to getting your changes done, not having anyone else working on the paper at the same time can be frustrating. Especially as a paper nears completion, and small changes are constantly being made by all authors, multitasking with CVS is definitely a plus.
But there are some issues with using a CVS which are more specific to scientific paper writing which make me think a paper collaboration CVS might be a really nice tool. Any ideas? Here is one idea:
Traditionally authors comment out sections which they change. Thus, for instance, if I am writing a new version of a paragraph, I will comment out the old version and keep it in the source. One reason for doing this is that it allows one to revert back fairly easily. With a CVS, of course, this is not strictly needed: the CVS is designed exactly to revert to prior version if necessary. But there is another reason why we comment out: we often cut and paste from the commented out component, or just want to quickly reread the commented out component as we write the new version. So the CVS needs some way of dealing with this technique: author’s want to have extremely easy access to previous versions. In fact what we really need is integration with an editor so I can turn on and off display of the “deleted” sections from prior version.
Schurly You're Joking Dr. Bacon
A new paper, a new paper! If you love the theory of the addition of angular momentum, and don’t we all just love the theory of the addition of angular momentum, then you will really love the new paper we (Isaac Chuang and Aram Harrow) just put on the arXiv. Unfortunately my spell check changed the title to Clench-Gordon and I didn’t notice. So I expect a lot of nasy emails complaining about the title. Doh. Well that’s what the replace button is for, I guess. Here is the paper:
quant-ph/0407082
Efficient Quantum Circuits for Schur and Clebsch-Gordon Transforms
Authors: Dave Bacon, Isaac Chuang, Aram Harrow
Comments: 4 pages, 3 figures
The Schur basis on n d-dimensional quantum systems is a generalization of the total angular momentum basis that is useful for exploiting symmetry under permutations or collective unitary rotations. We present efficient (size poly(n,d,log(1/epsilon)) for accuracy epsilon) quantum circuits for the Schur transform, which is the change of basis between the computational and the Schur bases. These circuits are based on efficient circuits for the Clebsch-Gordon transformation. We also present an efficient circuit for a limited version of the Schur transform in which one needs only to project onto different Schur subspaces. This second circuit is based on a generalization of phase estimation to any nonabelian finite group for which there exists a fast quantum Fourier transform.
Full-text: PostScript, PDF, or Other formats
Too Legit? Too Legit to Qubit?
Physical Review Letters has changed their sections around. Previously, quantum information was in the last section “Interdisciplinary Physics: Biological Physics, Quantum Information, etc.” For the more fundamental oriented papers, one would sometimes also submit to “General Physics.” Now quantum information has been moved to the new first section “General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.”
Is this a good thing? Since I am nothing if but a bag of poorly thought out opinions I will spew out some here. (1) It is nice to see that quantum information is consider a part of “General Physics.” “Interdisciplinary physics” seems a way to say, well there were these good physicists, and then they took interest in this other field which has overlap outside of physics, and since we liked these physicists we let them publish here. If I look at this move as acknowledging that quantum information has intrinsic value to physics, then I get goosebumps all over (sadly doubling the amount of stimulation I’ve had all day.) (2) The old “General Physics” section was notoriously harder to get papers accepted into if they had a quantum information tilt. Generally (err) this was because the papers submitted there were of a more foundational nature, and well, let’s not even go there. Will the movement of quantum information to general physics make it easier for foundational people to get published?
5ive Days to Midnight
Yesterday I subjected myself to the SciFi Channel minseries “5ive Days to Midnight.” Why would I subject myself to five hours of such torture? Well, the main character is a physicist and the plot involves time travel! That withstanding it was not a pretty site. First, because the dialogue was atrocious, but second because the main character is a physicist who lives in Washington (the state, that is!) Even the T.V. taunts me now.
I Doubt It
I hold that doubt is essential for the discovering and the understanding of the Truth…examine yourselves by that and scrutinize the very knowledge which you are supposed to have gained. For I tell you that orthodoxy is set up when the mind and heart are in decay…But when you invite doubt, it is as the rain washes away the dust of tradition, which is the dust of ages, the dust of belief, and leaves you certain of those things which are essential- one-time-messiah turned guru-in-denial J. Krishnamurti
Publish Noise
From an interview with Neal Stephenson:
Hooke, for example, when he figured out how arches work, published it as an anagram. He condensed the idea into this pithy statement: “The ideal form of an arch is the form of a chain hanging, flipped upside down.” Then he scrambled the letters to make an anagram and published it. That way, he wasn’t giving away the secret, but if somebody came along a few years later and claimed that they’d invented it, he could just unscramble what he’d published. He was establishing precedence.
How long until someone publishes a paper on the arXiv which is just noise and then, after some major result appears, says “No, I did this a long time ago, and here is the key which unscrambles my paper?