Scott Aaronson's Blog, page 57

Ask Me Anything! Tenure Edition

By popular request, for the next 36 hours—so, from now until ~11PM on Tuesday—I’ll have a long-overdue edition of “Ask Me Anything.”  (For the previous editions, see here, here, here, and here.)  Today’s edition is partly to celebrate my new, tenured “freedom to do whatever the hell I want” (as well as the publication after 7 years of Quantum Computing Since Democritus), but is mostly just to have an excuse to get out of changing diapers (“I’d love to, honey, but the world is demanding answers!”).  Here are the ground rules:

One question per person, total.
Please check to see whether your question was already asked in one of the previous editions—if it was, then I’ll probably just refer you there.
No questions with complicated backstories, or that require me to watch a video, read a paper, etc. and comment on it.
No questions about D-Wave.  (As it happens, Matthias Troyer will be giving a talk at MIT this Wednesday about his group’s experiments on the D-Wave machine, and I’m planning a blog post about it—so just hold your horses for a few more days!)
If your question is offensive, patronizing, nosy, or annoying, I reserve the right to give a flippant non-answer or even delete the question.
Keep in mind that, in past editions, the best questions have almost always been the most goofball ones (“What’s up with those painting elephants?”).

That’s it: ask away!

The Tenured Toll-Taker

On Friday afternoon—in the middle of a pizza social for my undergrad advisees—I found out that I’ve received tenure at MIT.

Am I happy about the news?  Of course!  Yet even on such a joyous occasion, I found myself reflecting on a weird juxtaposition.  I learned about MIT’s tenure decision at the tail end of a fierce, weeks-long comment war over on Luboš Motl’s blog, in which I assumed the task of defending theoretical computer science and quantum information science as a whole: explaining why these fields could have anything whatsoever to contribute to our understanding of the universe.  Indeed, I took the title of this post from a comment Luboš made to me in the middle of the comment war: that compared to string theorists, quantum computing researchers have as little to say about the nature of reality as toll-takers on the Golden Gate Bridge.  (Even though the Golden Gate tolls are apparently all-electronic these days, I still found Luboš’s analogy striking.  I could imagine that staring all day at the breathtaking San Francisco Bay would lead to deep thoughts about the nature of reality.)

Now, some people will ask: why should I even waste my time this way—arguing with Luboš, a blogger infamous for describing the scientists he disagrees with as garbage, worms, fungi, etc., and even calling for their “elimination”?  If I find the limits of computation in the physical universe to be a rich, fascinating, worthwhile subject; if I have hundreds of wonderful colleagues with whom to share the thrill of surprising new discoveries; if a large, growing fraction of the wider scientific community follows this field with interest, if my employer seems to want me doing it for the long haul … then why should I lose sleep just because someone, somewhere, declared that the P vs. NP problem is a random puzzle, of no deeper significance than whether or not chess is a draw?  Or because he characterized the entire field of quantum computing and information as a trivial footnote to 1920s physics, fit only for mediocre students who couldn’t do string theory?  Or because, on the “other side,” a persistent minority calls quantum computers an absurd fantasy, and the quest to build them a taxpayer boondoggle bordering on fraud?  Or because some skeptics, going even further, dismiss quantum mechanics itself as nonsensical mumbo-jumbo that physicists made up to conceal their own failure to find a straightforward, mechanical description of Nature?  Likewise, why should it bother me if some anti-complexites dismiss the quest to prove P≠NP as a fashionable-but-irrelevant journey to formalize the obvious—even while others denounce the Soviet-style groupthink that leads the “CS establishment” to reject the possibility that P=NP?  After all, these various naysayers can’t all be right!  Doesn’t it comfort me that, of all the confidently-asserted reasons why everything my colleagues and I study is dead-end, cargo-cult science, so many of the reasons contradict each other?

Sure, but here’s the thing.  In seven years of teaching and blogging, I’ve learned something about my own psychology.  Namely, if I meet anyone—an undergrad, an anonymous blog commenter, anyone—who claims that the P vs. NP problem is beside the point, since it’s perfectly plausible that P=NP but the algorithm takes n10000 time—or that, while quantum mechanics works fine for small systems, there’s not the slightest reason to expect it to scale up to larger ones—or that the limits of computation are plainly no more relevant to physics than the fact that cucumbers are green—trying to reason with that person will always, till the end of my life, feel like the most pressing task in the world to me.  And it will make no difference whether I’m an unknown postdoc and the other person is Emperor of the Galaxy, or vice versa.

Why?  Because, I confess, a large part of me worries: what if this other person is right?  What if I really do have to jettison everything I thought I knew about physics, computation, and pretty much everything else since I was a teenager, toss all my results into the garbage can (or at least the “amusing recreations can”), and start over from kindergarten?  But then, as I fret about that possibility, counterarguments well up in my mind.  Like someone pinching himself to make sure he’s awake, I remember all the reasons why I was led to think what I think in the first place.  And I want the other person to go through that experience with me—the experience, if you like, of feeling the foundations of the universe smashed to pieces and then rebuilt, the infinite hierarchy of complexity classes collapsing and then springing back into place, decades’ worth of books set ablaze and then rewritten on blank pages.  I want to say: at least come stand here with me—in this place that I spent twenty years of late nights, false starts, and discarded preconceptions getting to—and tell me if you still don’t see what I see.

That’s how I am; I doubt I can change it any more than I can change my blood type.  So I feel profoundly grateful to have been born into a world where I can make a comfortable living just by being this strange, thin-skinned creature that I am—a world where there are countless others who do see what I see, indeed see it a thousand times more clearly in many cases, but who still appreciate what little I can do to explore this corner or that, or to describe the view to others.  I’d say I’m grateful to “fate,” but really I’m grateful to my friends and family, my students and teachers, my colleagues at MIT and around the world, and the readers of Shtetl-Optimized—yes, even John Sidles.  “Fate” either doesn’t exist or doesn’t need my gratitude if it does.

“Closer to Truth”

Two years ago, when I attended the FQXi conference on a ship from Norway to Denmark, I (along with many other conference participants) was interviewed by Robert Lawrence Kuhn, who produces a late-night TV program called “Closer to Truth.”  I’m pleased to announce (hat tip: Sean Carroll) that four videos from my interview are finally available online:

Is the Universe a Computer?

(like a politician, I steer the question toward “what kind of computer is the universe?,” then start talking about P vs. NP, quantum computing, and the holographic principle)

What Does Quantum Theory Mean?

(here I mostly talk about the idea of computational intractability as a principle of physics)

Quantum Computing Mysteries

(basics of quantum mechanics and quantum computing)

Setting Time Aright (about the differences between time and space, the P vs. PSPACE problem, and computing with closed timelike curves)

(No, I didn’t choose the titles!)

For regular readers of this blog, there’s probably nothing new in these videos, but for those who are “just tuning in,” they provide an extremely simple and concise introduction to what I care about and why.  I’m pretty happy with how they came out.

Once you’re finished with me (or maybe even before then…), click here for the full list of interviewees, which includes David Albert, Raphael Bousso, Sean Carroll, David Deutsch, Rebecca Goldstein, Seth Lloyd, Marvin Minsky, Roger Penrose, Lenny Susskind, Steven Weinberg, and many, many others who might be of interest to Shtetl-Optimized readers.

Quantum Computing Since Democritus now out in the US! 20% discount for Shtetl-Optimized readers

OK, this will be my last blog post hawking Quantum Computing Since Democritus, at least for a while.  But I do have four pieces of exciting news about the book that I want to share.

Amazon is finally listing the print version of QCSD as available for shipment in North America, slightly ahead of schedule!  Amazon’s price is $35.27.
Cambridge University Press has very generously offered readers of Shtetl-Optimized a 20% discount off their list price—meaning $31.99 instead of $39.99—if you click this link to order directly from them.  Note that CUP has a shipping charge of $6.50.  So ordering from CUP might either be slightly cheaper or slightly more expensive than ordering from Amazon, depending (for example) on whether you get free shipping from Amazon Prime.
So far, there have been maybe 1000 orders and preorders for QCSD (not counting hundreds of Kindle sales).  The book has also spent a month as one of Amazon’s top few “Quantum Physics” sellers, with a fabulous average rating of 4.6 / 5 stars from 9 reviews (or 4.9 if we discount the pseudonymous rant by Joy Christian).  Thanks so much to everyone who ordered a copy; I hope you like it!  Alas, these sales figures also mean that QCSD still has a long way to go before it enters the rarefied echelon of—to pick a few top Amazon science sellers—Cosmos, A Brief History of Time, Proof of Heaven (A Neurosurgeon’s Journey into the Afterlife), Turn On Your SUPER BRAIN, or The Lemon Book (Natural Recipes and Preparations).  So, if you believe that QCSD deserves to be with such timeless classics, then put your money where your mouth is and help make it happen!
The most exciting news of all?  Luboš Motl is reading the free copy of QCSD that I sent him and blogging his reactions chapter-by-chapter!  So, if you’d like to learn about how mathematicians and computer scientists simply lack the brainpower to do physics—which is why we obsess over kindergarten trivialities like the Church-Turing Thesis or the Axiom of Choice, and why we insist idiotically that Nature use only the mathematical structures that our inferior minds can grasp—then check out Luboš’s posts about Chapters 1-3 or Chapters 4-6.  If, on the other hand, you want to see our diacritical critic pleasantly surprised by QCSD’s later chapters on cryptography, quantum mechanics, quantum computing, then here’s the post for you.  Either way, be sure to scroll down to the comments, where I patiently defend the honor of theoretical computer science against Luboš’s hilarious ad hominem onslaughts.

Superiority of the Latke: The Unexpected Convergence of Quantum Mechanics and Common Sense

Back in February, I gave a talk with the above title at the Annual MIT Latke-Hamentaschen Debate.  I’m pleased to announce that streaming video of my talk is now available!  (My segment starts about 10 minutes into the video, and lasts for 10 minutes.)  You can also download my PowerPoint slides here.

Out of hundreds of talks I’ve given in my life, on five continents, this is the single talk of which I’m the proudest.

Of course, before you form an opinion about the issue at hand, you should also check out the contributions of my fellow debaters.  On the sadly-mistaken hamentasch side, my favorite presentation was that of mathematician Arthur Mattuck, which starts in at 56 minutes and lasts for a full half hour (!! – the allotted time was only 8 minutes).  Mattuck relates the shapes of latkes and hamentaschen to the famous Kakeya problem in measure theory—though strangely, his final conclusions seem to provide no support whatsoever for the hamentaschen, even on Mattuck’s own terms.

Finally, what if you’re a reader for whom the very words “latke” and “hamentaschen” are just as incomprehensible as the title of this blog?  OK, here are some Cliff Notes:

Latkes are fried potato pancakes, traditionally eaten by Jews on Hannukah.
Hamentaschen are triangular fruit-filled cookies, traditionally eaten by Jews on Purim.
Beginning at the University of Chicago in 1946, many universities around the world have held farcical annual “debates” between faculty members (both Jewish and non-Jewish) about which of those two foods is better.  (The reason I say “farcical” is simply that, as I explain in my talk, the truth has always been overwhelmingly on one side.)  The debaters have invoked everything from feminist theory to particle physics to bolster their case.

Thanks very much to Dean of Admissions Stu Schmill for moderating, and to MIT Hillel for organizing the debate.

Update: Luboš has a new blog post announcing that he finally found a chapter in Quantum Computing Since Democritus that he likes!  Woohoo!  Whether coincidentally or not, the chapter he likes makes exactly the same points about quantum mechanics that I also make in my pro-latke presentation.

I was right: Congress’s attack on the NSF widens

Last month, I blogged about Sen. Tom Coburn (R-Oklahoma) passing an amendment blocking the National Science Foundation from funding most political science research.  I wrote:

This sort of political interference with the peer-review process, of course, sets a chilling precedent for all academic research, regardless of discipline.  (What’s next, an amendment banning computer science research, unless it has applications to scheduling baseball games or slicing apple pies?)

In the comments section of that post, I was pilloried by critics, who ridiculed my delusional fears about an anti-science witch hunt.  Obviously, they said, Congressional Republicans only wanted to slash dubious social science research: not computer science or the other hard sciences that people reading this blog really care about, and that everyone agrees are worthy.  Well, today I write to inform you that I was right, and my critics were wrong.  For the benefit of readers who might have missed it the first time, let me repeat that:

I was right, and my critics were wrong.

In this case, like in countless others, my “paranoid fears” about what could happen turned out to be preternaturally well-attuned to what would happen.

According to an article in Science, Lamar Smith (R-Texas), the new chair of the ironically-named House Science Committee, held two hearings in which he “floated the idea of having every NSF grant application [in every field] include a statement of how the research, if funded, ‘would directly benefit the American people.’ “  Connoisseurs of NSF proposals will know that every proposal already includes a “Broader Impacts” section, and that that section often borders on comic farce.  (“We expect further progress on the μ-approximate shortest vector problem to enthrall middle-school students and other members of the local community, especially if they happen to belong to underrepresented groups.”)  Now progress on the μ-approximate shortest vector problem also has to directly—directly—”benefit the American people.”  It’s not enough for such research to benefit science—arguably the least bad, least wasteful enterprise our sorry species has ever managed—and for science, in turn, to be a principal engine of the country’s economic and military strength, something that generally can’t be privatized because of a tragedy-of-the-commons problem, and something that economists say has repaid public investments many, many times over.  No, the benefit now needs to be “direct.”

The truth is, I find myself strangely indifferent to whether Smith gets his way or not.  On the negative side, sure, a pessimist might worry that this could spell the beginning of the end for American science.  But on the positive side, I would have been proven so massively right that, even as I held up my “Will Prove Quantum Complexity Theorems For Food” sign on a street corner or whatever, I’d have something to crow about until the end of my life.

My fortune-cookie wisdom for the day

On Sunday afternoon, Dana, Lily, and I were in Copley Square in Boston for a brunch with friends, at the Mandarin Oriental hotel on Boylston Street.  As I now recall, I was complaining bitterly about a number of things.  First, I’d lost my passport (it’s since been found).  Second, we hadn’t correctly timed Lily’s feedings, making us extremely late for the brunch, and causing Lily to scream hysterically the entire car ride.  Third, parking (and later, locating) our car at the Prudential Center was a logistical nightmare.  Fourth, I’d recently received by email a profoundly silly paper, claiming that one of my results was wrong based on a trivial misunderstanding.  Fifth … well, there were other things that were bothering me, but I don’t remember what they were.

Then the next day, maybe 50 feet from where we’d been, the bombs went off, three innocent human beings lost their lives and many more were rendered permanently disabled.

Drawing appropriate morals is left as an exercise for the reader.

QStart conference in Jerusalem, June 24-27

Friend-of-the-blog Dorit Aharonov asked me to advertise the QStart Conference, which will be held at Hebrew University of Jerusalem June 24-27 of this year, to celebrate the opening of Hebrew University’s new Quantum Information Science Center.  Speakers include Yakir Aharonov, Jacob Bekenstein, Hans Briegel, Ed Farhi, Patrick Hayden, Ray Laflamme, Elon Lindenstrauss, Alex Lubotzky, John Martinis, Barbara Terhal, Umesh Vazirani, Barbara Terhal, Stephanie Wehner, Andrew Yao … and me, your humble blogger (who will actually be there with Lily, on her first trip abroad—or for that matter, beyond the Boston metropolitan area).  Dorit tells me that the conference should be of interest to mathematicians, physicists, chemists, philosophers, and computer scientists; that registration is open now; and that student travel support is available.  Oh, and if you’re one of the people who think quantum computing is bunk?  As displayed on the poster above, leading QC skeptic Gil Kalai is a co-organizer of the conference.

“So You Think Quantum Computing Is Bunk?”

On Wednesday, I gave a fun talk with that title down the street at Microsoft Research New England.  Disappointingly, no one in the audience did seem to think quantum computing was bunk (or if they did, they didn’t speak up): I was basically preaching to the choir.  My PowerPoint slides are here.  There’s also a streaming video here, but watch it at your own risk—my stuttering and other nerdy mannerisms seemed particularly bad, at least in the short initial segment that I listened to.  I really need media training.  Anyway, thanks very much to Boaz Barak for inviting me.

Pigs sprouted wings, Hell froze over, and I guest-posted on Luboš Motl’s blog

Furthermore, the last of those things actually happened.  What won’t I do to promote Quantum Computing Since Democritus?  Enjoy!

Update: I submitted the following response to the comments over on Lubos’s blog.  Since it has some bits of general interest, I thought I’d crosspost it here while it awaits Lubos’s moderation.

Since Lubos “officially invited” me to respond to the comments here, let me now do so.

1. On “loopholes” in quantum mechanics: I completely agree with Lubos’s observation that the actual contents of my book are “conservative” about the truth of QM. Indeed, I predict that, when Lubos reads his free copy, he’ll agree with (or at least, have no objections to) the vast majority of what’s in the book. On the other hand, because I was guest-blogging about “the story of me and Lubos,” I found it interesting to highlight one area of disagreement regarding QM, rather than the larger areas of agreement.

2. On Gene Day’s patronizing accusation that I don’t “get the basics of QM or even comprehend the role of mathematics in physics”: his misreading of what I wrote is so off-base that I don’t know whether a response is even necessary.  Briefly, though: of course two formulations of QM are mathematically equivalent if they’re mathematically equivalent!  I wasn’t asking why we don’t use different mathematical structures (quaternions, the 3-norm, etc.) to describe the same physical world.  I was asking why the physical world itself shouldn’t have been different, in such a way that those other mathematical structures would have described it.  In other words: if you were God, and you tried to invent a theory that was like QM but based on those other structures, would the result necessarily be less “nice” than QM?  Would you have to give up various desirable properties of QM?  Yes?  Can you prove it?  The ball’s in your court, Mr. Day — or else you can just read my book!

3. On Lord Nelson’s accusation that I’m a “poseur”: on reflection, someone who only knew me from blog stunts like this one could easily be forgiven for getting that impression! So it might be worth pointing out for the record that I also have a “day job” outside the blogosphere, whose results you can see here if you care.

4. On my political views: I wish to clarify for Tom Vonk that I despise not only “Communists,” but the ideology of Communism itself. One of the formative experiences of my life occurred when I was an 8-year-old at Wingate Kirkland summer camp, and all the campers had to relinquish whatever candy they’d brought into a communal “bunk trunk.” The theory was that all the campers, rich and poor alike, would then share the candy equally during occasional “bunk parties.” What actually happened was that the counselors stole the candy. So, during a meeting of the entire camp, I got up and gave a speech denouncing the bunk trunk as Communism. The next day, the camp director (who had apparently been a fellow-traveler in the 1950s) sat with me at lunchtime, and told me about a very evil man named Joe McCarthy who I was in danger of becoming like. But the truth was that I’d never even heard of McCarthy at that point — I just wanted to eat candy.  And I’d give exactly the same speech today.

Like (I suppose) several billion of the world’s people, I believe in a dynamic market-based capitalist society, and also in strong environmental and other regulations to safeguard that society’s continued existence. And I don’t merely believe in that as a cynical compromise, since I can’t get the “dictatorship of the proletariat” that I want in my heart of hearts. Were I emperor of the world, progressive capitalism is precisely what I would institute. In return, perhaps, for paying a “candy tax” to keep the bunk functioning smoothly, campers could keep their remaining candy and eat or trade it to their heart’s delight.

5. On climate change: I’m not a professional climatologist, but neither is Lubos, and nor (correct me if I’m wrong) is anyone else commenting here. Accordingly, I refuse to get drawn into a debate about ice cores and tree rings and hockey sticks, since my experience is that such debates tend to be profoundly unilluminating when not conducted by experts. My position is an incredibly simple one: just like with the link between smoking and cancer, or the lack of a link between vaccines and autism, or any other issue where I lack the expertise to evaluate the evidence myself, I’ll go with what certainly looks like an overwhelming consensus among the scientists who’ve studied the matter carefully. Period. If the climate skeptics want to win me over, then the way for them to do so is straightforward: they should ignore me, and try instead to win over the academic climatology community, majorities of chemists and physicists, Nobel laureates, the IPCC, National Academies of Science, etc. with superior research and arguments.

To this, the skeptics might respond: but of course we can’t win over the mainstream scientific community, since they’re all in the grip of an evil left-wing conspiracy or delusion!  Now, that response is precisely where “the buck stops” for me, and further discussion becomes useless.  If I’m asked which of the following two groups is more likely to be in the grip of a delusion — (a) Senate Republicans, Freeman Dyson, and a certain excitable string-theory blogger, or (b) virtually every single expert in the relevant fields, and virtually every other chemist and physicist who I’ve ever respected or heard of — well then, it comes down to a judgment call, but I’m 100% comfortable with my judgment.