Computer scientists crash the Solvay Conference

Thanks so much to everyone who sent messages of support following my last post! I vowed there that I’m going to stop letting online trolls and sneerers occupy so much space in my mental world. Truthfully, though, while there are many trolls and sneerers who terrify me, there are also some who merely amuse me. A good example of the latter came a few weeks ago, when an anonymous commenter calling themselves “String Theorist” submitted the following:

It’s honestly funny to me when you [Scott] call yourself a “nerd” or a “prodigy” or whatever [I don’t recall ever calling myself a “prodigy,” which would indeed be cringe, though “nerd” certainly —SA], as if studying quantum computing, which is essentially nothing more than glorified linear algebra, is such an advanced intellectual achievement. For what it’s worth I’m a theoretical physicist, I’m in a completely different field, and I was still able to learn Shor’s algorithm in about half an hour, that’s how easy this stuff is. I took a look at some of your papers on arXiv and the math really doesn’t get any more advanced than linear algebra. To understand quantum circuits about the most advanced concept is a tensor product which is routinely covered in undergraduate linear algebra. Wheras in my field of string theory grasping, for instance, holographic dualities relating confirmal field theories and gravity requires vastly more expertise (years of advanced study). I actually find it pretty entertaining that you’ve said yourself you’re still struggling to understand QFT, which most people I’m working with in my research group were first exposed to in undergrad 😉 The truth is we’re in entirely different leagues of intelligence (“nerdiness”) and any of your qcomputing papers could easily be picked up by a first or second year math major. It’s just a joke that this is even a field (quantum complexity theory) with journals and faculty when the results in your papers that I’ve seen are pretty much trivial and don’t require anything more than undergraduate level maths.

Why does this sort of trash-talk, reminiscent of Luboš Motl, no longer ruffle me? Mostly because the boundaries between quantum computing theory, condensed matter physics, and quantum gravity, which were never clear in the first place, have steadily gotten fuzzier. Even in the 1990s, the field of quantum computing attracted amazing physicists—folks who definitely do know quantum field theory—such as Ed Farhi, John Preskill, and Ray Laflamme. Decades later, it would be fair to say that the physicists have banged their heads against many of the same questions that we computer scientists have banged our heads against, oftentimes in collaboration with us. And yes, there were cases where actual knowledge of particle physics gave physicists an advantage—with some famous examples being the algorithms of Farhi and collaborators (the adiabatic algorithm, the quantum walk on conjoined trees, the NAND-tree algorithm). There were other cases where computer scientists’ knowledge gave them an advantage: I wouldn’t know many details about that, but conceivably shadow tomography, BosonSampling, PostBQP=PP? Overall, it’s been what you wish every indisciplinary collaboration could be.

What’s new, in the last decade, is that the scientific conversation centered around quantum information and computation has dramatically “metastasized,” to encompass not only a good fraction of all the experimentalists doing quantum optics and sensing and metrology and so forth, and not only a good fraction of all the condensed-matter theorists, but even many leading string theorists and quantum gravity theorists, including Susskind, Maldacena, Bousso, Hubeny, Harlow, and yes, Witten. And I don’t think it’s just that they’re too professional to trash-talk quantum information people the way commenter “String Theorist” does. Rather it’s that, because of the intellectual success of “It from Qubit,” we’re increasingly participating in the same conversations and working on the same technical questions. One particularly exciting such question, which I’ll have more to say about in a future post, is the truth or falsehood of the Quantum Extended Church-Turing Thesis for observers who jump into black holes.

Not to psychoanalyze, but I’ve noticed a pattern wherein, the more secure a scientist is about their position within their own field, the readier they are to admit ignorance about the neighboring fields, to learn about those fields, and to reach out to the experts in them, to ask simple or (as it usually turns out) not-so-simple questions.

I can’t imagine any better illustration of these tendencies better than the 28th Solvay Conference on the Physics of Quantum Information, which I attended two weeks ago in Brussels on my 41st birthday.

As others pointed out, the proportion of women is not as high as we all wish, but it’s higher than in 1911, when there was exactly one: Madame Curie herself.

It was my first trip out of the US since before COVID—indeed, I’m so out of practice that I nearly missed my flights in both directions, in part because of my lack of familiarity with the COVID protocols for transatlantic travel, as well as the immense lines caused by those protocols. My former adviser Umesh Vazirani, who was also at the Solvay Conference, was proud.

The Solvay Conference is the venue where, legendarily, the fundamentals of quantum mechanics got hashed out between 1911 and 1927, by the likes of Einstein, Bohr, Planck, and Curie. (Einstein complained, in a letter, about being called away from his work on general relativity to attend a “witches’ sabbath.”) Remarkably, it’s still being held in Brussels every few years, and still funded by the same Solvay family that started it. The once-every-few-years schedule has, we were constantly reminded, been interrupted only three times in its 110-year history: once for WWI, once for WWII, and now once for COVID (this year’s conference was supposed to be in 2020).

This was the first ever Solvay conference organized around the theme of quantum information, and apparently, the first ever that counted computer scientists among its participants (me, Umesh Vazirani, Dorit Aharonov, Urmila Mahadev, and Thomas Vidick). There were four topics: (1) many-body physics, (2) quantum gravity, (3) quantum computing hardware, and (4) quantum algorithms. The structure, apparently unchanged since the conference’s founding, is this: everyone attends every session, without exception. They sit around facing each other the whole time; no one ever stands to lecture. For each topic, two “rapporteurs” introduce the topic with half-hour prepared talks; then there are short prepared response talks as well as an hour or more of unstructured discussion. Everything everyone says is recorded in order to be published later.

Daniel Gottesman and I were the two rapporteurs for quantum algorithms: Daniel spoke about quantum error-correction and fault-tolerance, and I spoke about “How Much Structure Is Needed for Huge Quantum Speedups?” The link goes to my PowerPoint slides, if you’d like to check them out. I tried to survey 30 years of history of that question, from Simon’s and Shor’s algorithms, to huge speedups in quantum query complexity (e.g., glued trees and Forrelation), to the recent quantum supremacy experiments based on BosonSampling and Random Circuit Sampling, all the way to the breakthrough by Yamakawa and Zhandry a couple months ago. The last slide hypothesizes a “Law of Conservation of Weirdness,” which after all these decades still remains to be undermined: “For every problem that admits an exponential quantum speedup, there must be some weirdness in its detailed statement, which the quantum algorithm exploits to focus amplitude on the rare right answers.” My title slide also shows DALL-E2‘s impressionistic take on the title question, “how much structure is needed for huge quantum speedups?”:

The discussion following my talk was largely a debate between me and Ed Farhi, reprising many debates he and I have had over the past 20 years: Farhi urged optimism about the prospect for large, practical quantum speedups via algorithms like QAOA, pointing out his group’s past successes and explaining how they wouldn’t have been possible without an optimistic attitude. For my part, I praised the past successes and said that optimism is well and good, but at the same time, companies, venture capitalists, and government agencies are right now pouring billions into quantum computing, in many cases—as I know from talking to them—because of a mistaken impression that QCs are already known to be able to revolutionize machine learning, finance, supply-chain optimization, or whatever other application domains they care about, and to do so soon. They’re genuinely surprised to learn that the consensus of QC experts is in a totally different place. And to be clear: among quantum computing theorists, I’m not at all unusually pessimistic or skeptical, just unusually willing to say in public what others say in private.

Afterwards, one of the string theorists said that Farhi’s arguments with me had been a highlight … and I agreed. What’s the point of a friggin’ Solvay Conference if everyone’s just going to agree with each other?

Besides quantum algorithms, there was naturally lots of animated discussion about the practical prospects for building scalable quantum computers. While I’d hoped that this discussion might change the impressions I’d come with, it mostly confirmed them. Yes, the problem is staggeringly hard. Recent ideas for fault-tolerance, including the use of LDPC codes and bosonic codes, might help. Gottesman’s talk gave me the insight that, at its core, quantum fault-tolerance is all about testing, isolation, and contact-tracing, just for bit-flip and phase-flip errors rather than viruses. Alas, we don’t yet have the quantum fault-tolerance analogue of a vaccine!

At one point, I asked the trapped-ion experts in open session if they’d comment on the startup company IonQ, whose stock price recently fell precipitously in the wake of a scathing analyst report. Alas, none of them took the bait.

On a different note, I was tremendously excited by the quantum gravity session. Netta Engelhardt spoke about her and others’ celebrated recent work explaining the Page curve of an evaporating black hole using Euclidean path integrals—and by questioning her and others during coffee breaks, I finally got a handwavy intuition for how it works. There was also lots of debate, again at coffee breaks, about Susskind’s recent speculations on observers jumping into black holes and the quantum Extended Church-Turing Thesis. One of my main takeaways from the conference was a dramatically better understanding of the issues involved there—but that’s a big enough topic that it will need its own post.

Toward the end of the quantum gravity session, the experimentalist John Martinis innocently asked what actual experiments, or at least thought experiments, had been at issue for the past several hours. I got a laugh by explaining to him that, while the gravity experts considered this too obvious to point out, the thought experiments in question all involve forming a black hole in a known quantum pure state, with total control over all the Planck-scale degrees of freedom; then waiting outside the black hole for ~1070 years; collecting every last photon of Hawking radiation that comes out and routing them all into a quantum computer; doing a quantum computation that might actually require exponential time; and then jumping into the black hole, whereupon you might either die immediately at the event horizon, or else learn something in your last seconds before hitting the singularity, which you could then never communicate to anyone outside the black hole. Martinis thanked me for clarifying.

Anyway, I had a total blast. Here I am amusing some of the world’s great physicists by letting them mess around with GPT-3.

Back: Ahmed Almheiri, Juan Maldacena, John Martinis, Aron Wall. Front: Geoff Penington, me, Daniel Harlow. Thanks to Michelle Simmons for the photo.

I also had the following exchange at my birthday dinner:

Physicist: So I don’t get this, Scott. Are you a physicist who studied computer science, or a computer scientist who studied physics?

Me: I’m a computer scientist who studied computer science.

Physicist: But then you…

Me: Yeah, at some point I learned what a boson was, in order to invent BosonSampling.

Physicist: And your courses in physics…

Me: They ended at thermodynamics. I couldn’t handle PDEs.

Physicist: What are the units of h-bar?

Me: Uhh, well, it’s a conversion factor between energy and time. (*)

Physicist: Good. What’s the radius of the hydrogen atom?

Me: Uhh … not sure … maybe something like 10-15 meters?

Physicist: OK fine, he’s not one of us.

(The answer, it turns out, is more like 10-10 meters. I’d stupidly substituted the radius of the nucleus—or, y’know, a positively-charged hydrogen ion, i.e. proton. In my partial defense, I was massively jetlagged and at most 10% conscious.)

(*) Actually h-bar is a conversion factor between energy and 1/time, i.e. frequency, but the physicist accepted this answer.

Anyway, I look forward to attending more workshops this summer, seeing more colleagues who I hadn’t seen since before COVID, and talking more science … including branching out in some new directions that I’ll blog about soon. It does beat worrying about online trolls.

116 Responses to “Computer scientists crash the Solvay Conference”

  1. Ian Finn Says:

    This was awesome to read, thanks so much for sharing!

  2. badspeler Says:

    >Physicist: What are the units of h-bar?

    >Me: Uhh, well, it’s a conversion factor between energy and time. (*)

    >Physicist: Good. What’s the radius of the hydrogen atom?

    >Me: Uhh … not sure … maybe something like 10^-15 meters?

    >Physicist: OK fine, he’s not one of us.

    This made me laugh out loud. I think the “correct answer” is “about an ångström” and maybe add in something like, “I only use cgs units not that SI trash.”

  3. Rand Says:

    [I don’t recall ever calling myself a “prodigy,” which would indeed be cringe, though “nerd” certainly —SA]

    “Still, I was what some people would call a “child prodigy,” what with the finishing my PhD at 22 and whatnot, so naturally that colored my reaction to the show.”


  4. Joshua Zelinsky Says:

    The complaint that so much of what you is linear algebra seems weird at two levels. First, there’s a lot of subtle things that happen just in linear algebra. The second is that from a pedagogical standpoint, one of the things that makes me at least sort of understand some quantum computing at all is that you’ve made it so clear that so much of it really is just linear algebra. And part of what makes many of your papers *readable* to non-experts is how well you really make clear where the linear algebra is coming in. So it sounds like part of the mistake here is that commenter is mistaking you having a very good explanatory approach and thinking that that somehow means what you are doing is easy. (In contrast to say a lot of the number theory and graph theory I do, which honestly really is pretty easy stuff with much less abstraction.)

  5. Rand Says:

    That said, the criticism is pretty laughable, especially if you have any familiarity with It from Qubit and the surrounding work.

    Or if you read this blog.

    Or if you read Quanta.

    Or if you’ve heard of the MIP* result (because some of the CS stuff is hard too and resolves hard _math_ problems!).

  6. PDE and CS Says:

    As an engineer, I had a hold-my-nose-and-compute attitude to PDEs until a friend introduced me to the Feynman-Kac formula, which connects PDEs and stochastic processes. That in turn led me to a partial understanding of some beautiful results by Cedric Villani and colleagues, connecting PDEs, geometry, entropy and optimization. The last two are very much CS topics.

  7. Michael Ball Says:

    Maybe you should have estimated the radius in Electronvolts?

    Thanks for the post, brought a smile to my face.

  8. Scott Says:

    Rand #3: Once in 17 years, because it was directly relevant to what I was writing and I couldn’t figure out an alternative formulation, and even then, I used the sort of evasive formulation pioneered by Jesus when his disciples asked him whether he was the Messiah (“so people have said”) 😀

  9. Daniel Harlow Says:

    Honestly I expect that this anonymous “string theorist” is not a very good string theorist, judging a scientist by how fancy their mathematics is is like judging a carpenter by how expensive their tools are. Some tasks require expensive tools and some don’t, and it is only an idiot who buys the expensive ones when they aren’t needed. In fact there have been several Nobel prizes in physics given for diagonalizing 2×2 or 3×3 matrices; it is all about knowing which matrix to diagonalize!

  10. Scott Says:

    Daniel Harlow #9: Great analogy! Of course, many theoretical computer scientists do now use some fearsomely expensive tools, ones fashioned for them just within the last couple of decades by Gromov and Tao and Gowers and the like. It’s a subset of us who stick, whenever possible, to whatever we can do with a constant-sized hammer and a polynomial amount of duct tape… 🙂

  11. Scott Says:

    Joshua Zelinsky #4: Yeah, I’d tend to agree with the claim that quantum computing is “just linear algebra,” but would generalize it to the claim that 90% of everything is just linear algebra! 🙂

    Granted, when my physicist friends whip out their Euclidean path integrals, it does seem incomprehensibly deeper than anything I’ve ever worked on. A little copy of the commenter “String Theorist” even appears inside my own head to sneer at me. But then, a minute later, the very same physicists who’d been analytically continuing replica wormholes like nobody’s business might ask me to explain to them why PSPACE is contained in EXP, or even how the Bell/CHSH inequality works, and as I explain it, my self-confidence slowly returns. 🙂

  12. Robert Rand Says:

    Scott #8:

    ‘Scott Aaronson compares himself to Jesus Christ. Concerning whether or not he was the Messiah, “so people have said”.’

  13. Scott Says:

    Robert Rand #12: The trouble is that I’ve been reading screenful after screenful of Eliezer Yudkowsky lately, to the point where discussing the question of one’s own Messiah-hood seemed normal and unexceptionable. 😀

  14. Rand Says:

    Scott #11: “You can only fit so many things in PSPACE until you get back back to the first thing”.

  15. Scott Says:

    OK, one story I can’t resist sharing. When, in the late 1950s, Paul Cohen acquired the suspicion that set theory was trivial and shallow compared to the kind of math he did, he arguably earned the right to his suspicion, by taking off a few years to solve set theory’s greatest unsolved problems (the independence of the Axiom of Choice and the Continuum Hypothesis), and winning the Fields Medal and eternal glory for it.

    I’d invite commenter “String Theorist,” in the warmest and most emphatic terms, to do the analogous thing with quantum complexity theory. Certainly no one can accuse us of hiding what our great open problems are.

  16. Scott Says:

    Rand #14: Yes, that’s the proof.

  17. Paul Bunch Says:

    Mr. Anonymous String Theorist sounds like the kind of guy who likes the smell of his own farts.

  18. Craig Says:

    Scott, if it makes you feel better, the theory of quantum computing is wrong, while string theory is not even wrong, so you are more of a scientist than your string theorist critic.

  19. Scott Says:

    Craig #18: Thanks, I’ll look forward to your refutation of quantum computing theory as well your not-even-refutation of string theory!

    Though if, as scientists, we’re supposed to be actually responsive to data, over the past few years the Google and USTC quantum supremacy experiments showed errors nearly uncorrelated between gates—and if that trend continues, then quantum fault-tolerance will ultimately work! Gil Kalai and the other QC skeptics have had a lot of work cut out for them to explain this away. 🙂

  20. Yonah Borns-Weil Says:

    Hi Scott,

    Will you by any chance be at QMath in Davis this September? (Then you’ll get to be a computer scientist in a conference of physicists AND mathematicians)

  21. Scott Says:

    Yonah #20: Sorry, I don’t think so!

  22. Luboš Motl Says:

    What the “string theorist” wrote isn’t trash talk but a collection of totally obviously true and fundamentally important facts about the fields that are being deliberately obfuscated by a movement that doesn’t belong to the Academia but that has thoroughly contaminated it, anyway.

    Like that user (and probably many other string theorists), I have also mastered Shor’s algorithm in about 30 minutes and I optimized its teaching so that I could teach it in 30 minutes, too. If someone had asked me to write down a quantum algorithm doing what Shor’s algorithm does, I am pretty sure that I would have done (invented) it within days, too.

    Those are true observations. Most of this field is just overhyped linear algebra (I co-wrote a linear algebra textbook as an undergraduate freshman) combined with the optimization of P.R. Everyone in that field who claims to be on par with string theorists is just a plain fraudster and the real reasons why you don’t care is that you also know it is obvious; and the mediocre minds such as yourself (and assorted woke and perverse garbage of mankind) have actually acquired the core powers over the Academia and turned it into hospices for people who aren’t good at anything. The likes of you are also brainwashing the new generations and elevating the filth of those generations above the gems so that you preserve your power.

    The fraudsters like you may have conquered the tools of brainwashing and claim that everyone is equal and you are the peer of string theorists. But you still can’t change the truth and it will always be the case that you are about as analogous to a string theorist as manure is isomorphic to gold.

    Quantum computing is just an overhyped application of undergraduate freshman mathematics. Research-level string theory is about 10 years of expertise and 1-in-100 degree of selection above that. People like you are enthusiastic about promoting woke lies and similar garbage exactly because you know that you can align yourself with this garbage well while you have no chance to reach the level of genuine world class scholarship.

  23. kodlu Says:

    is there a list of participants somewhere?

  24. Scott Says:

    Luboš #22: Welcome back! And then please see yourself out again. 😀

    It must sting to see Susskind, Maldacena, Witten, and so many of your other stringy heroes (or ex-heroes?) come to a point of view on these matters that’s so remote from yours. Juan was joking with me a few years ago about how, when I came to meet with him in 2004 about the computational complexity of simulating black hole dynamics, and whether it might exceed BQP (this is back when I was a postdoc in the School of Mathematics at IAS), it sounded like a wild juxtaposition from out of nowhere. And yet now, less than two decades later, such wild juxtapositions seem to be taking over your whole field—or former field.

  25. LK2 Says:

    Scott, as a physicist I envy you a lot for participating to the Solvay conference. Maybe in some decades the photo you posted will become iconic like to one containing Schroedinger & Co 😉
    You could start by producing a black-and-white version of it!

    QC question now: you state that the error independence is pretty well proved (for now) by two experiments. Would be possible that this were true only for this kind of circuit sampling tasks, but will fail in a “classical” (!) QC task like applying a sequence of gates to a bunch of qbits for running a computation like Shor or something simpler?
    In essence, the question is: is a proof based on circuit sampling sufficient for settling this issue?

    Don’t bother about string theorists: some of them are getting increasingly nervous since after few decades of adoration, the public is getting bored by the total absence of results connected to reality. We have only one QFT which is well verified by the data and it is called the Standard Model. I wonder if complexity papers exist (never found) discussing the complexity difference for example between perturbative QED and perturbative QCD, or in other words what is the difference in complexity between abelian and non-abelian QFTs…

  26. Scott Says:

    LK2 #25:

    – I mean, the only fully convincing experimental demonstration that it’s possible to run Shor’s algorithm … will be to run Shor’s algorithm!

    But after the sampling-based supremacy experiments, if you don’t believe that fault-tolerant QCs running Shor’s algorithm will ultimately be possible, then I’d say that the burden falls squarely on you to explain the difference between the two cases. Will Nature somehow “notice” that you’re trying to build fault-tolerant qubits, and conspire to thwart you? A few skeptics, most notably Gil Kalai, have tried to develop models where something like that would be true. My personal view is that they’ve been spectacularly unsuccessful so far—and indeed, since they’re smart people, that their failure constitutes evidence that such a model won’t be easy to find. That said, if they turned out to be right, of course that would be a scientific revolution, and a hundred times more exciting than a mere “success” in building scalable QCs.

    – As I took pains to point out, I’m under no illusions that “String Theorist” (or Luboš, for that matter) represent the majority of string theorists. In fact, my experience over the past decade has been the exact opposite.

    – Yes, there’s been a whole line of work over the past decade on the computational complexity of simulating interacting QFTs—starting with the 2011 paper by Jordan, Lee, and Preskill, which showed how to simulate φ4 theory (e.g., a Higgs field) using a standard qubit-based QC. While there have been many followups, my understanding is that the full Standard Model has remained out of reach, in part because of issues related to chiral fermions. But there’s a huge number of subtleties even just in defining what it is that you want your quantum algorithm to calculate. To me, it seems more principled to define the computational problem nonperturbatively whenever possible (e.g., using lattice models), and then to treat perturbation as just one calculational technique, which might or might give a sensible answer, and which part of the whole point of a QC would be to let you bypass.

  27. Aspect Says:

    It’s so nostalgic: a post about a cool conference where both CS and physics people attend, fun discussions about QC and related topics, and Lubos in the comments talking mad trash.
    This is like the early/pre-2010 era 🙂

  28. Scott Says:

    kodlu #23: Sorry! With enough effort, the participants could be identified from the photo, but I’m not going to do it. In any case it’s not secret and will be in the published proceedings.

  29. Jon Says:

    Re: quantum simulation of \(\phi^4\) theory, is there a principled argument for why this is classically hard? This might be hard to answer given the lack of definition of what the problem is, of course.

    I have in mind the following (vigorously) hand-waving argument that suggests it could be classically easy: combine the Jerrum-Sinclair algorithm for the Ising model with the Griffiths-Simon trick for expressing Euclidean \(\phi^4\) theory as a superposition of Ising models. Is there a computational subtlety in the transfer of information to Minkowski signature?

  30. Andrew White Says:

    Looks like a great workshop, and I *love* the photo at dinner. I’m not sure if it counts, but there was an earlier Solvay workshop on quantum information-y things:

    “First Solvay Workshop on Bits, Quanta, and Complex Systems : modern approaches to photonic information processing, organized by the International Solvay Institutes Brussels, April 30th – May 3rd, 2008”.

  31. Ivo Says:

    “String Theorist” is pretty confused about what makes things hard if they believe it is the height of the tower of knowledge necessary to address a question that matters. The height of the tower is a measure of how specialized they are, not of how difficult it is to become that specialized.

    A question that just requires primary school knowledge can be equally difficult to answer as one that requires a PhD in string theory to answer. What matters is how parts of that knowledge need to be combined to come to an answer. Whether you need to combine 150 theorems about Calabi-Yau manifolds or 150 about ‘trivial’ linear algebra makes no difference.

  32. LK2 Says:

    Hi Scott and thank you very much for the extensive answer.

    My point was not that nature sees I’m running Shor and invents something to prevent it.
    What I mean was something more trivial, like the “averaging” or the structure itself of circuit
    sampling might shadow somehow correlations which can LIMIT (not completely prevent) other types of quantum computations.
    Probably my view is biased by being a physicist and having a kind of “feeling” about how hard it is to protect quantum states.

    Thus the question: is this possibility mathematically ruled out (by people other than Kalai) or we really have “just” to wait and see?

  33. Alex Says:

    Comment #22 As an immunologist that is interested in quantum computing I’m quite sure that I’m “not really good at anything”. I’m sure I can’t understand Shor’s algorythm – neither in 30 min nor 30 months, but what I do understand is that insulting colleagues on the internet is unprofessional and that your worldview has long since ceased to have a future. Still, I’d be very interested in reading your current paper – if you had any.

  34. Logan Says:

    Hi Scott, I for one am pleased to hear that you’ve had enough of your troll-related angst period. Mind you, it does you great credit that you have taken these matters to heart, but it is not your best blogging material.
    Now, I well know that age does this to all of us, but truly you were once absolutely hilarious in your posts. I hope that life might arrange for you to find your inner comedian once again (apart from being a brilliant scientist) because that is the best Scott, or at least the best blogging Scott.

  35. Anthony Says:

    Scott #28: the list is here for instance:

  36. Mitchell Porter Says:

    A reminder that if someone can prove whether or not P=NP – they can use linear algebra, string theory, or anything in between – there’s a million dollars to be won…

  37. Triceratops Says:

    I cannot believe a human being sat down at a computer, typed out that comment, and hit submit. Good grief.

    Some people do not appreciate the wonderful gift of life.

  38. Set theorist Says:

    Sadly, this sentiment of “my field is superior to yours” is echoed among many mathematicians as well, including some very competent ones (though most of them will usually express it in more subtle and implicit ways). When I encounter such claims, my way to “win the argument” is to ask them about the most advanced result from my field that they understand. Usually it will turn out to be some undergrad-level stuff. So in the case of the anti-QC trolls above, I would guess that:

    1. Shor’s algorithm is the most advanced result in QC that they understand.

    2. They might not even understand Shor’s algorithm that well.

    3. They will never understand MIP^*=RE (due to intellectual laziness).

  39. Ted Says:

    Scott, please let us know when the recordings/transcripts are published!

    I know that this is an extremely crude oversimplification of both your Aaronson-Ambainis Conjecture and the Yamakawa-Zhandry result, but my naive understanding is that the former says that “No random oracle problem admits an exponential quantum speedup,” while the latter says that “Some random oracle problem admits an exponential quantum speedup.” But at you say that the two propositions are 100% consistent, which means that my understanding of one or both of them is fundamentally incorrect. Could you please briefly clarify why the two propositions are consistent, and which of those crude summaries above is fundamentally wrong?

  40. Scott Says:

    LK2 #32: Yeah, I understood the question. Is there a theory that “naturally” kills quantum fault-tolerance, or makes it exponentially costly to implement, without killing sampling-based quantum supremacy—one that would only look like a conspiracy if you didn’t know what it was?

    Certainly there’s no mathematical proof that such a theory is impossible (what would such a proof even look like? what assumptions would it rest on?). I personally find it implausible: it’s as if someone were trying to prove in the 1830’s that, while special-purpose, noisy, probabilistic classical computations are of course possible, Babbage’s dream of a reliable universal digital computer is inevitably doomed to failure. I.e. it’s a statement about the current technological limits of civilization rather than the ultimate limits of Nature, and is therefore precisely the sort of thing that’s only true until it isn’t! But that’s just my intuition: go read Gil Kalai’s stuff, for example, and see how plausible you find it!

  41. Scott Says:

    Set theorist #38: In my experience, it’s ridiculously easy to delude yourself into thinking you understand something, the gaps being exposed only when you either

    (1) try to explain it to others (that’s why teaching is great!), or
    (2) try to build on, generalize, or improve it.

    In particular, the following statement is childish yet true: anyone who thinks they could’ve easily invented Shor’s algorithm is welcome to convince the world by inventing the next great quantum algorithm.

    (It’s true that anyone working now has the disadvantage that much of the low-hanging fruit has been picked—but they also have the advantage of knowing what general sort of thing to look for!)

  42. Scott Says:

    Ted #39: It’s explained in my previous post, but … Aaronson-Ambainis says that there’s no exponential quantum speedup relative to a random oracle for algorithms that output yes/no answers. The Yamakawa-Zhandry algorithm does not output a yes/no answer. It solves an NP search problem (that is, it finds an n-bit string that satisfies some constraint). That’s it. That’s the entire difference, and the reason why the two statements are compatible.

  43. Scott Says:

    Logan #34: Thanks! Alas, I’ve learned firsthand just how much harder it is to be funny when so many more people—not just the trolls and sneerers but your colleagues, your students, CEOs, university presidents, whatever—are watching what you say and holding you to a certain standard of conduct. Can you imagine if I tried to do another biting vaginas post today? 😀 Or maybe that’s just what I tell myself, when the reality is that I’ve simply gotten old, tired, and unfunny. But I promise you this: I will continue trying to corner the market for quantum-complexity-theory-related humor.

  44. Scott Says:

    Jon #29: That’s a great question! We don’t actually know whether the scattering problem solved by the Jordan-Lee-Preskill algorithm is classically hard. Definitely see, however, this followup paper, where they show that, if you add a controllable external classical potential, then the problem becomes BQP-hard (i.e., as hard as any other quantum computation, including Shor’s algorithm).

  45. John Preskill Says:

    Others have made this point already, but I’ll chime in.

    I recall being asked by colleagues in the 1990s whether after 20 years of doing particle theory I ever felt embarrassed about working on the far less sophisticated field of quantum computing (“just linear algebra”). But I never felt that way (well, hardly ever).

    It’s certainly true that it requires far less background to understand Shor’s algorithm or the concept of a quantum error-correcting code than to understand AdS/CFT duality (though in both cases it took me considerably longer than half an hour). That did not make Shor’s algorithm or quantum error correction easy to discover, nor does it diminish the scientific implications of either discovery.

    Incidentally, it was quantum error correction even more than superpolynomial quantum computational speedups that convinced me that quantum information science would have a long-term impact on physical science and encouraged me to steer my own research in that direction. It’s interesting to see how quantum error correction is becoming an essential theme of research in both quantum condensed matter and quantum gravity.

  46. Raoul Ohio Says:

    Kind of funny having a “String Theorist” casting shade on QC!

    QC is something that might actually work and be useful. Although my guess for the likelihood of a “useful” QC result ever occurring is 50% at best, the payoff would probably be huge, so the mathematical expectation is pretty good.

    On the other hand, a reasonable estimate for the likelihood of ST ever doing ANYTHING useful is about 1% at best. Furthermore, ST is sucking down a large fraction of physics funding, and also wasting the careers of many graduate students. The grad students will be OK, because skill in advanced math translates well, but if they think they will be the next Einstein, I suggest that they not hold their breath.

  47. Raoul Ohio Says:

    Lubos #22:

    Thanks for sharing.

  48. Michel Says:

    Lubos #22 : This really sounds to me like: My artwork is more beautiful because it is made of gold, while your artwork is only made of simple stone. Don’t look at the art, look at the material!

    Ever looked at the David by Michelangelo?Just stone.

  49. Alex Gezerlis Says:

    Those who dismiss entire research fields as “just” linear algebra would do well to peruse Wilkinson’s treatise on the algebraic eigenvalue problem. As noted in the Preface, the eigenvalue problem has a deceptively simple formulation and the background theory is well-established, but that doesn’t mean that mastering the topic is trivial.

  50. LK2 Says:

    Scott #40: thanks again for your extended answer: I will not bother you further with other questions (even as I would like to 😉 ). It is exactly because I read Kalai’s stuff that I wanted to hear (read?) your opinion. I still have a lot to think about all this.
    Thank you very much again!

  51. matt Says:

    Scott #15, you say that we don’t hide what our great open problems are, but I’m not sure about that. Of course, there are problems like separating P and PSPACE, but such problems are far too difficult to call great open problems. There’s your own personal lists of annoying problems, but some of those are more annoying than great. There’s questions like “find a new quantum algorithm”, but it would be better to have a problem that is stated more mathematically “prove that …” because it is more clear what it mean to solve it (we can argue about which quantum algorithm really are new). But what do you think the great open problems are? I remember at one point there being a nice webpage of great open problems in QI, and being inspired to consider some of those problems, but I don’t know an analogue today.

  52. Scott Says:

    matt #51: I think P vs. PSPACE does qualify as a great open problem—the fact that it’s so hard is our problem, not the problem’s problem! Short of that, though, there’s derandomizing polynomial identity testing, RL vs. L, superquadratic lower bounds on arithmetic complexity of the permanent … and in quantum computing, the quantum PCP question (as you well know), QMA vs QCMA, quantum algorithms for lattice problems and dihedral HSP, a Mahadev-style protocol with no cryptographic assumptions, the hardness of approximate BosonSampling (or other sampling tasks), and more. Obviously as the questions get less insanely hard, they also get more abstruse: were that not the case, they would’ve already been solved!

  53. Greg Rosenthal Says:

    Scott #13: I suspect you’re referring to Harry Potter and the Methods of Rationality (if not, I’m curious what you’re reading since it sounds engrossing) in which case you might like to know that there’s an excellent audiobook version of it:

  54. Scott Says:

    Greg Rosenthal #53: Thanks! As it happens, my 9-year-old daughter Lily and I have been reading HPMOR together (we’re now about 75% through). But in addition, I just read Eliezer’s brand-new litany o’ doom, about why it’s now virtually inevitable that AI will wipe out the human race, the latter having ignored Eliezer’s warnings for the past 20 years (read it and then tell me if that’s an inaccurate characterization).

  55. Ted Says:

    Scott #42 My apologies for missing that discussion in your previous post, as it’s buried a bit of a ways down in the comments. For the benefit of any other readers with my same question: the discussion is in comments #19-23 at

    Even though it isn’t a counterexample, does the Yamakawa-Zhandry result decrease your confidence in the Aaronson-Ambainis conjecture at all? Or do you think that search problems and decision problems are different enough beasts that the YZ result doesn’t affect the likelihood of the AA conjecture much?

  56. Alex Says:

    Hi Scott. As a mathematical physicist, I don’t really see with good eyes how people like string theorists are now also playing with the ideas of your field. If I were you, I would be worried, because everything they touch, they transform it into pseudoscience. And since they are attached to influential places and institutions in the US, they use their positions to force their “ideas” to the detriment either of the original ideas or of some other approaches in the same field (if they contradict a comma of their dogma). You mentioned you were not a physicist. As one, and knowing first hand the damage that string theorists have done to fundamental physics, I would suggest you to approach all of those things you mention (in a seemingly positive view) with much more skepticism, you may be inviting a Trojan Horse computer virus (bad pun intended) to your field. In fact, most string theorists are rather mediocre, they just live from the image of people like Witten (who does know the math), and don’t really have a fraction of the mathematical knowledge they claim to have (they only tend to know some rudiments of this and that). In your case, even if you “only use linear algebra”, the conceptual problems are much harder and richer than many ill-formulated pseudo-technical problems in string theory.

  57. Scott Says:

    Alex #56: Thanks for the concern! But I think quantum complexity theory is a grown adult who can make its own decisions about whom to associate with, and who doesn’t need to be rescued from rapacious string theorists. 😀

    What caught my attention was when, again and again, Susskind and the other string theorists were able to give me problems that were interesting to me as quantum computing theory, even if I completely removed the motivating story involving black holes or AdS/CFT. But then also, the motivating story, insofar as I understood it, struck me as raising conceptual questions of a sort that would eventually need to be faced in nearly any quantum theory of gravity.

    For the truth is that, while I call these people “string theorists” (and while they still call themselves that), in all my conversations with them, there’s been nary a string, superparticle, or curled-up extra dimension (let alone a landscape of them) anywhere. Instead, it’s been all about smashing the well-accepted principles of QM, QFT, and GR into each other in clever thought experiments involving black holes and wormholes, while typically using AdS/CFT (or rather, vaguely-AdS/CFT-flavored toy models) as a playground to make the discussion concrete. While it’s true that AdS/CFT originally came from string theory, now that it exists the actual strings seem to have been discarded like scaffolding for most questions of interest!

    In any case, none of my discussions or collaborations with the string theorists have required me to make any commitment whatsoever about the reality of strings, supersymmetry, or extra dimensions in our universe, let alone at accessible energies.

  58. Scott Says:

    Ted #55: To be honest, my confidence in the AA conjecture is dented only slightly if at all. (And for whatever it’s worth, Yamakawa and Zhandry say that they still believe the AA conjecture—indeed, they even assume it to prove one of the side results in their paper!)

    Once you switch attention from decision and promise problems to sampling and search problems, we actually already knew that exponential quantum speedups were possible relative to a random oracle (see for example my Forrelation paper). We “just” didn’t know that those search problems could also be put into NP! This supports the view, for which we have other evidence as well, that sampling and search problems are just a different ballgame.

  59. Douglas Knight Says:

    Why does this sort of trash-talk…no longer ruffle me?

    Your answer seems to buy into the framing, that the point of the field, of “advanced intellectual achievement” is an intelligence test. You are no longer afraid of physicists because you have held your own against the ones that entered the field. What a sad, zero-sum view! Whereas you used to justify your choice of field by saying that it was a good field, aimed at fundamental philosophy and stringent test of quantum mechanics. You could frame this as a different test of personal virtue: the good taste to choose an important field, perhaps more amenable to progress than string theory. Or you could reject the framing of personal virtue entirely.

  60. Douglas Knight Says:

    And to be clear: among quantum computing theorists, I’m not at all unusually pessimistic or skeptical, just unusually willing to say in public what others say in private.

    Does the concept of NISQ function as an easy way to communicate to people that we can’t do anything? But people aren’t willing to spell out even that?

  61. ppnl Says:

    Paul Bunch #17:

    That reminds me of a quote I barely remember from decades ago:

    “I suspect that more people enjoy the smell of their own farts than is popularly supposed.”

    I do not know the source. I only get a vague echo of Asimov but have not been able to find any reference. I swear if I can’t find a reference I’m going to claim it as my own!

  62. ppnl Says:

    Scott #40:

    Well their have been such conspiracies before. Nobody could explain why you couldn’t construct Maxwell’s Demon. It turns out that there is a very elegant conspiracy that prevents Maxwell’s demon. Finding it built a bridge between thermodynamics and computer science. Nearly a hundred years after Maxwell proposed his demon we got the Landauer limit.

    I have long suspected that the deeper understanding of quantum information that the quantum computer question will cause will be necessary for progress in string theory and/or quantum gravity. We will either build QCs or understand why they can’t be built. Either way it will light the path forward. We may just have to wait a hundred years.

  63. Scott Says:

    Douglas Knight #59: Almost all of us think we’re trying to understand the world, not merely prove our intelligence … if the latter, then why not just do competitive chess, or math or programming contests, or take IQ tests like Marilyn vos Savant?

    All the same, it would obviously sting if everything in your field, the field you’d spent your whole career on, were laughably trivial to someone from a different field. So, when an asshole from a different field does come along to claim that, it seems like 100% fair game to ask the asshole to solve your field’s great open problems—provided your field has great open problems that plausibly have solutions that could be found today and that everyone would recognize as valid—and to send the asshole away with extreme prejudice if they can’t do it.

  64. Scott Says:

    Douglas Knight #60: No. While plenty of cringeworthy hype has attached itself to the term, “NISQ” was originally coined, and is still used by experts, simply as a way to talk about what we can or can’t do before we have fault-tolerance. It’s not secret code for something other than that.

  65. Scott Says:

    ppnl #62: I’ll happily settle for lighting the path forward! 🙂

  66. James Gallagher Says:

    AdS/CFT is definitely one of the most hyped UNPHYSICAL ideas ever in all of Science – and the genius String Theory community are to blame – promoting a fantastical mathematical coincidence as if God himself couldn’t do any better!

    We don’t live in anti-de Sitter Space so it should be dS/CFT, and a conformal field theory can easily be substituted for something as simple as a random process, so we really should just have dS/(Random Number Generator) as the more realistic and general model

  67. Scott Says:

    James Gallagher #66: Honest question—how well do you understand AdS/CFT?

  68. Daniel Chantry Says:

    Everything is part of the big puzzle, from maths 5o English and computer science to physicists…you cannot solve the things you want until all piece of the puzzle work together, so dont say, he is not one of us else you are shutting the door on a possibility.
    Everything links like an electron to an atom.
    If it connects on a particle level then it all connects on an educational level

  69. John K Clark Says:

    The fellow calling himself “String Theorist” seems to be saying that string theory is superior to computer science because the mathematics used is much more convoluted, and never mind the fact that all that advanced mathematics has never been able to find anything useful and string theory can’t produce even one testable prediction. As for me I say there is no point in adding more bells and whistles to the mathematics used than what is needed to get the job done.

    John K Clark

  70. Job Says:

    The way to dismiss a whole field of study is to do so while praising the efforts of those involved.

    If you just do it while personally attacking someone, in a here’s what I think of you and your field kind of way, nobody takes it seriously.

    Also, you are only the intellectual others grant you to be. You can’t be forceful about it, it’s counterproductive.

    These are basic observations.

  71. Raoul Ohio Says:

    ppnl #62

    I have also thought “maybe there is something like Maxwell’s Demon” behind the empirical observation that certain engineering challenges seem to show a negative rate of progress. There are many very hard steps, maybe infinitely many, to get to something that works.

    Is it like Zeno’s paradox, where you have a convergent series? Or is it like the harmonic function, where you keep adding on smaller and smaller terms, but the sum is unbounded?

    Two illustrative examples:

    1. Controlled nuclear fusion: In my recollection, 60 years ago we would have free electricity in about 5 or 10 years. Now there might be “breakeven” in maybe 20 years.

    2. Quantum computing: There have been regular announcements of different flavors of “Quantum Supremacy” from Google, IBM, startups in strip malls, and whatnot. For each, we debate “did it calculate anything?”, “is it faster than an Apple II?”, etc. Sometimes it turns out that if you squint, right at twilight, that it kind of works on some problem invented to utilize the contraption. So there’s that. But the time frame for “when can I get one at newegg to do some factoring” seems to growing.

    Either or both of these worthy endeavours might turn out to be like:

    A: Building an airplane: a lot of people got banged up for decades, but now they got it figured out.

    B: Transmuting lead into gold: Alchemists hung in there for millennia without much luck. Along the way, however, they invented chemistry (giving hope that String Theorists might figure something out).

    Who knows? It is fun being a sideline spectator, monitoring progress.

  72. GCT Says:

    Isn’t GCT tough? Wouldn’t that qualify as a difficult topic?

  73. Olivier Says:

    When you have a high profile, it’s pretty clear that some trolls are going to invent a game of trying to piss off the great Scott Aaronson. I’d suspect most (reasonable) people who follow don’t actually post or comment on anything, just reading, so you’re clearly getting a highly biased sample of the people out there, which a unnaturally high proportion of trolls trying to get a reaction out of you that they think they could go parade around as a trophy, for whatever trollic ritual it’s involved in.

  74. bystander Says:

    @Luboš Motl: If someone had asked me to […] Shor was able to find it out w/o being asked.

    @Scott: Regarding BHIP, were you presented only with the Page curve way, or with the other approaches too? BTW If you cannot even imagine that your work would have some measurable consequences, I cannot imagine that you do physics.

  75. Greg Rosenthal Says:

    Scott #54: Accurate characterization.

  76. Shmi Says:

    Scott, I hope to see you writing up your reflections on Eliezer’s doomposting. None of it seems obviously wrong to me, provided one accepts that agentic superintelligence is a thing that can exist. I guess one counter-argument would be “if it were possible and as drastic as predicted by Eliezer, it would have observable cosmological effects by now.”

  77. Nick Drozd Says:

    Lubos Motl #22

    > Like that user (and probably many other string theorists), I have also mastered Shor’s algorithm in about 30 minutes and I optimized its teaching so that I could teach it in 30 minutes, too. If someone had asked me to write down a quantum algorithm doing what Shor’s algorithm does, I am pretty sure that I would have done (invented) it within days, too.

    There are few people in England, I suppose, who have more true enjoyment of music than myself, or a better natural taste. If I had ever learnt, I should have been a great proficient.

  78. Scott Says:

    Nick Drozd #77: LOL, had to look that one up! Pride and Prejudice.

  79. Scott Says:

    Shmi #76: Reflections a-comin’! I’m actually in the Bay Area now, and will be meeting in person with Eliezer and a bunch of other thinkers about AI alignment next week.

  80. Scott Says:

    GCT #72:

      Isn’t GCT tough? Wouldn’t that qualify as a difficult topic?

    GCT is definitely tough—in fact I’ve often described it as “the string theory of computer science”!

    On the other hand, which should be considered more “impressive”: someone who’s mastered the geometric invariant theory, representation theory, quantum groups, and Langlands-type correspondences needed to seriously discuss GCT, but can’t yet use them to say anything new about computation, or someone who uses much more elementary techniques (e.g. basic combinatorics and linear algebra) but can say something new?

  81. Lorraine Ford Says:

    Most theoretical physicists seemingly spend their entire working lives trying to mathematically model a type of world where people could never have any input to the system.

    These physicists envision and model a type of world where laws of nature and randomness are 100% responsible for every outcome (i.e. every number for every variable). I.e. these physicists envision and model a type of world where there could be no inputs (i.e. number assignments to variables) from people or other living things.

    In other words, these physicists envision and model a type of world where Vladimir Putin, and what Putin does, are just normal, unremarkable, outcomes of the evolution of the mathematical system, because they don’t envision a world where Putin could have any input (i.e. number assignments to variables) to the system.

    The Solvay Conference was presumably just another display of physics’ hard-line dystopian vision of the type of world we live in.

  82. Boaz Barak Says:

    Nice to see the blog getting back to standard trash talk of CS vs physics 🙂
    It is a shame that almost all physicists are already on our side, makes things less interesting 🙂

    Re Yudkowski’s doom predictions, I hope to write more at some point but my short take is

    Specifically, the scenarios he comes up to destroy the world are ones that don’t seem to require some extreme intelligence, and even humans could do it. Similarly, the scenarios he comes up with to prevent them (“burn all GPUs”) don’t seem to require extreme intelligence either.

    I don’t think this holds for all the people worried about AI risk but this particular text read less than predictions than a science fiction or superheroes story. The superpower here happens to be intelligence but it’s not clear it’s essential to the plot.

  83. Scott Says:

    Lorraine Ford #81:

      The Solvay Conference was presumably just another display of physics’ hard-line dystopian vision of the type of world we live in.

    As someone who was actually there, I can tell you that I don’t remember the question of free will ever really coming up at all.

  84. James Gallagher Says:

    #67 Scott

    I understand the difference between AdS and dS (which is non-trivial), and I have studied CFTs in some real-world applications too, but I don’t have much understanding of Maldacena’s celebrated work.

    My comment was rather meant as a sarcastic reply to “String Theorist” in your OP. I mean as far as I am concerned, QM describes the whole Universe and it is just Linear Algebra (+ randomness) – so eventually, all Physics will be explained by “simple” Linear Algebra.

  85. Lorraine Ford Says:

    Scott #83:
    I guess the point I’m getting at is that, despite experimental results, if physicists envision the world to be a certain way, the models will follow the vision (as well as the experimental results).

    It’s a pretty big thing to claim that Putin (or anyone else) is responsible for outcomes. A claim that Putin (or anyone else) is responsible for outcomes requires that the system we live in to be such that entities/ people actually have input to the system (i.e. people assign numbers to variables). This is a very different vision of the world to the usual physics’ vision of the type of world we live in.

  86. Craig Says:

    In my opinion, the most important subject in science is demography, even though the math is trivial compared to string theory – you cannot do science if there are no people. Demography is everything.

  87. Scott Says:

    Lorraine Ford #85: For what it’s worth, I can testify that there were lunch conversations at Solvay about the vileness of Vladimir Putin (along with various tactical aspects of the war in Ukraine). Like all such discussions, these assumed the existence of free will for practical purposes.

  88. Raoul Ohio Says:

    Are we witnessing Lorraine Ford’s creation of “Putin Theory”, a new branch of physics? Don’t know where it is going, but I predict linear algebra will be useful.

  89. Danny Says:

    I found your response to the arrogant commenter a little disappointing, to be honest. I didn’t feel it prudent to engage in a defense of quantum computing and argue that the burgeoning field’s complexity makes it just as “legitimate” as string theory—doing so in fact vindicates the premise of his so-called argument, that there are some fields intrinsically more “advanced” and “better” than other fields, when most of us (hopefully) agree that such a view is absolute piffle.

  90. Vladimir Says:

    >Physicist: What are the units of h-bar?

    >Physicist: What’s the radius of the hydrogen atom?

    FYI, the best answers to these questions are “it’s dimensionless” and “one Bohr radius” 😛

  91. ppnl Says:

    Scott #87:

    The thing about free will is that it takes a real effort of will not to believe in it.

  92. wolfgang Says:


    what was the many-body session about?

  93. Ari T Says:

    Honestly that email you got in the first blockquote, sounds exactly like Luboš. Someone who is obsessed about creating some sort of “hardest field” signalling game. The intellectual fashion show. What would Robin Hanson say – well we know what he would (I think I’m still missing the blog post where he discussed the very same problem).

    I am not going to have an opinion about the string theory as valid physics (it could well be, whatever), because that is not my point, but string theory like anything super hard is exactly an example of impressive signalling which attracts status-conscious folk.

    More importantly, the people I know who are super smart, the ones I respect, are always very kind, humble and never brag about their (fields’) intelligence. The people you like to talk to and learn from. I like to think Scott is in this category, and I’d be happy to hear I’m not alone in this.

  94. Anthony Says:

    Scott, thanks a lot for this post!
    How would you compare the Solvay conference to more typical workshops: do you think that the discussions among a group of a chosen few have led to more new/deeper insights than what happens in more standard venues? Said otherwise, should we hold our breath for the proceedings of the discussions with the hope of finding exciting original insights in there?

  95. Scott Says:

    wolfgang #92:

      what was the many-body session about?

    It was about many-body physics. 😀

    Frank Verstraete spoke. Area laws, and the role of quantum information in understanding them, definitely made an appearance, as did MPS and tensor networks.

  96. Scott Says:

    Anthony #94: Honest answer … I’d expect the official proceedings to have nice summaries of the various topics, well worth reading if you’re looking for that, but not to contain anything world-changing. By far the highest value that I personally got came from the lunches and coffee breaks and receptions. I’ll write in a future post about one of the most important things I learned. (Teaser: it has to do with black holes, the Quantum Extended Church-Turing Thesis, AdS/CFT, the mind/body problem, brain uploading, and fully homomorphic encryption. Yes, really. 🙂 )

    Interestingly, apparently at the 1927 Solvay Conference — the most famous one at all — the Einstein-Bohr debates about quantum mechanics appear nowhere in the official proceedings! They mostly took place at breakfast. 🙂

  97. GCT Says:

    “someone who’s mastered the geometric invariant theory, representation theory, quantum groups, and Langlands-type correspondences needed to seriously discuss GCT, but can’t yet use them to say anything new about computation, or someone who uses much more elementary techniques (e.g. basic combinatorics and linear algebra) but can say something new?”

    The former is definitely impressive beyond any reasonable doubt. Probably the tools don’t fit in to solve the computational complexity problems which are low key anyways. The expert probably has other things to do than discover elementary algorithms and write pages on pages for publication which anyway can be ultimately condensed to a few pages in a textbook down the road. Even Terence Tao’s papers are mostly a couple of dozen pages. I wonder why algorithm papers run into so many more pages. Something has to be done to standardize things so they can be written precisely and condensed even when they are to be published rather than wait for textbook condensation later. But I agree certain insights in algorithms are impressive.

  98. Lorraine Ford Says:

    Scott #87:
    Why pretend that free will exists “for practical purposes”, when that is actually just a big lie about what they really think about the nature of the world?

    Physicists’ models of the world can’t explain in principle how a person, like Vladimir Putin, could be responsible for his own outcomes; the models say that it is the laws of nature and randomness that are responsible for every aspect of every outcome. Physics’ models are missing something important about the world because the models can’t cope with people having input to the world, i.e. people having a genuine effect on the world. Only something like a computer system model of the world could potentially cope with that aspect of the world.

  99. Qwerty Says:

    Do consider getting TSA pre-check. Shorter security lines, atleast. It is like the Disneyworld fastpass – pay more to be in shorter lines.

    You get it by filling some forms and going to a govt building and getting background checks and fingerprinted, etc. Ofcourse, they make you pay something for the faster and shorter line! Huge time-saver if you travel often. The U.S will not require covid tests to enter the U.S, from midnight tonight.

  100. ppnl Says:

    Lorraine Ford #87:

    But physics can’t explain subjective experiences so we are left with a mystery any way you cut it.

    It is not that I believe in free will. I think our experience of free will is created by the fact that we experience our thoughts. It is not necessarily a thing any more than the qualia “red” is a thing out there. But there is still a mystery out there.

    In the end we have little choice but to act as if we have free will.

  101. OhMyGoodness Says:

    Not sure if it was the influence of the computer scientists but there are an astounding number of people smiling in the group photo compared to the funerary photos of Solvay Conferences past.

  102. phi Says:

    Lorraine Ford #98:

    Have you heard of the compatibilist [1] idea of free will? This is the notion that Putin and other humans are responsible for their actions, even if at the lowest level they are just big piles of atoms following fixed rules. Physicists aren’t lying when they say they believe in free will, they just don’t think there is a contradiction between being made of atoms and being able to make one’s own decisions and have moral responsibility for those decisions.


  103. Tamás V Says:

    I have to admit I first misread it as “String Terrorist” 🙂 That guy definitely hasn’t heard of the Egg of Columbus.

  104. asdf Says:

    Scott, why is it that Daniel Harlow is the only one in that photo wearing a mask? Don’t you have a Jewish mother to tell you to read and do all the stuff it says, then wear a mask everywhere except maybe at home?

    Regarding math technique, see : “A (likely apocryphal) story goes: when Peter Lax was awarded the National Medal of Science, the other recipients (presumably non-mathematicians) asked him what he did to deserve the Medal. Lax responded: “I integrated by parts.” (per Willie Wong but I’ve seen the story elsewhere too).

  105. Anthony Says:

    Scott #96:
    Thanks! It’s true that it makes sense that new ideas would be discussed more during breaks than during overly formatted scientific sessions.

    Looking forward to your future post where you explain the links between all these topics!

  106. James Harlin Says:


    Looking forward to your argument/explanation about the extended quantum Church-Turing thesis and (I presume) why it’s not violated even for an observer in a black hole. It’d be strange wouldn’t it that a certain place in the Universe would effectively allow for that? My intuition simply says it has to hold everywhere and at all times like QM. But I’m all up for a surprise if that’s the truth of the matter.

  107. asdf Says:

    Scott #54 “my 9-year-old daughter Lily and I have been reading HPMOR together (we’re now about 75% through)” OMG. How is she liking it so far? Were you able to explain the Buchholz hydra to her (chapter 100)? There is a wikipedia article about it now…

  108. Lorraine Ford Says:

    ppnl #100:
    In your second paragraph you seem to be saying that free will is an illusion. The implication is that you are not genuinely responsible for what your body does; presumably you are saying that it is the laws of nature and randomness that are responsible for each and every outcome in the entire universe, including what your body does.

    However, the legal system takes a different view, about what you do, and about what Vladimir Putin does. The legal system says that you are genuinely responsible for what your body does; to put it another way, the legal system says that you are assigning at least some of the numbers to some of your own variables. Is Putin responsible for what he is doing or not?

  109. Lorraine Ford Says:

    phi #102:
    No matter what some old philosophers might try to argue, free will means: “the power of acting without the constraint of necessity or fate”, where necessity and fate are the laws of nature and randomness.

    If all outcomes, including one’s own bodily outcomes, are due to the laws of nature and randomness, then free will is totally superfluous. If every number for each and every variable is due to the laws of nature and randomness, then free will is totally superfluous.

  110. asdf Says:

    Lorraine Ford,

    > The legal system says that you are genuinely responsible for what your body does;

    That makes it sound like the legal system has free will of its own, to make such a choice. Maybe it is all a consequence of an initial quantum state, and the apparent free will is just an illusion.

  111. Lorraine Ford Says:

    asdf #110:
    Is what Vladimir Putin is doing “just an illusion” in people’s minds? Are the people maimed and killed, and the cities razed to the ground, just an illusion? Is Vladimir Putin responsible for what he is doing, or is that just an illusion too?

  112. red75prime Says:

    Lorraine Ford #109: No metaphysical free will, fine. We still need to ponder physically impossible counterfactuals to make decisions, isolate unruly individuals (for damage control and rehabilitation), “someone is genuinely responsible” becomes “this lump of atoms is an autonomous intelligent agent that made such and such transgression(s), while having intact reasoning and predictive cognitive modules, and could be modified by arguing and, maybe, rehabilitation, instead of, say, medications”.

    Maybe it’s easier to redefine “free will” and be done with it.

  113. ppnl Says:

    Lorraine Ford #108:

    I don’t know. It seems odd that I get to experience the world but have no say in what happens. But I don’t get to make the rules and I don’t even get a rule book.

    Free will is so poorly defined that the question may be meaningless. I focus on the mystery of experience itself. Solve that and then maybe we can talk about free will.

  114. Lorraine Ford Says:

    red75prime #112 and ppnl #113:
    Free will is only superfluous IF all outcomes in the world, including one’s own bodily outcomes, are due to the laws of nature and randomness. I.e. free will is only superfluous IF every number for each and every variable is due to the laws of nature and randomness.

    But that is not the type of world we live in. We live in a type of world where people ARE genuinely responsible for their own outcomes, a type of world where Vladimir Putin IS genuinely responsible for what he has done.

    I.e. we live in a type of world where people are assigning at least some numbers to their own variables, in response to the situation they find themselves in.

  115. DeepSpace Says:

    There ought to be an analogous “dark information” \emph{inside} the blackhole so that total information is preserved, i.e., the quantity “information+darkinformation” remains unchanged on either side of the event horizon. This would also neatly resolve the AMPS firewall paradox, and address some of the questions raised by Lenny Susskind on the validity of QECTT inside a blackhole.

    For the latter, I would expect something like “computation done using dark information inside a blackhole cannot be more powerful than quantum computation”

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