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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.

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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.)”

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Heavenly Tasks

The young girl across from me in the Toronto airport is reading “The Five People you Will Meet in Heaven.” Which got me thinking: isn’t that nice, all these cool people who you’d never get a chance to talk to, will be your pals in heaven. But why does their eternal bliss in heaven involve a conversation with you?

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Reality Propaganda

Philip Dick has a famous quote about reality. Actually on the web you can find two versions of the quote:

Reality is that which, when you stop believing in it, doesn’t go away.

and

Reality is whatever refuses to go away when I stop believing in it.

If the second quote is correct, well Philip Dick died in 1982, and yet reality certainly exists, so Philip Dick must not have died in 1982. So I decided to stop believing in the second quote. And yet the second quote remains.

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Hallelujah

Listening to Jeff Buckley’s version of Leonard Cohen’s “Hallelujah,” I did a Google search and was surprised to find that
The Hallelujah Chorus is Satanic!!!
Go ahead, click on the link.
Good thing that Buckley’s version doesn’t have any drums! But the question is, if we aren’t to be literal, then where do we draw our lines? Why isn’t Buckley’s song canonized? It seems he knows the secret chord (E minor?)

I heard there was a secret chord
that David played and it pleased the Lord
But you don’t really care for music, do you?
Well it goes like this :
The fourth, the fifth, the minor fall and the major lift
The baffled king composing Hallelujah

But King David, probable author of many Psalms, not caring for the music? Or is it the almighty who doesn’t care for music? As the prophet Homer Jay might say, “Mmm, Sacrelicious.”
On a David note: I have often wondered how my parents knew that I would have red hair (well it was red when I was a wee lad!), considering neither of my parents had red hair. Hindsight on imagined precognition is what I practice here at the Quantum Pontiff!

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The Guitar of Time Travel

Inside of physicist Dave, behind skiing Dave, squished under happy Dave, there lies just a tiny bit of music Dave. Today I did something I haven’t done in too long a time—I picked up my guitar and played a few songs. OK, I have no talent! I’m blonde: whateeever!
Strumming my guitar on a warm Southern California evening put me in mood nostalgic for similar days spent in the summer of 96 sitting in front of the house at 270 Holliston. Which in turn reminded me of the man who sold the world.

We passed upon the stair
we spoke of was and when
Although I wasn’t there
he said I was his friend
Which came as some surprise
I spoke into his eyes
I thought you died alone
a long long time ago
Oh no, not me
I never lost control
You’re face to face
With The Man Who Sold The World
I laughed and shook his hand
and made my way back home
I searched for form and land
for years and years I roamed
I gazed a gazely stare
at all the millions here
We must have died along
a long long time ago
Who knows? not me
We never lost control
You’re face to face
With the Man who Sold the World
–David Bowie

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One Large Sundial

On my way home from Yreka for my sister’s birthday, I stopped by the Sundial Bridge in Redding, CA. It is a very strange feeling seeing this gigantic foot bridge over the Sacramento river in the middle of little old Redding. Here are a few pictures:



The bridge was designed by Santiago Calatrava, who also designed the olympic stadium for the upcoming olympics in Rome. On the summer solstice, the bridge acts as a large sundial. I wonder if anthropologists 4000 years from now will wonder what we used this gigantic sundial for?
RuhRoh Update: Panos points out that the olympics are in Athens not Rome. God am I an idiot these days: what was I thinking? Also it is the roof of the stadium which is being designed by Calatrava, not the whole stadium. See the comment section for some pictures of the stadium.

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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.

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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

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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?