Ask Me Anything: Apocalypse Edition

March 18th, 2020

So far, I confess, this pandemic is not shaping up for me like for Isaac Newton. It’s not just that I haven’t invented calculus or mechanics: I feel little motivation to think about research at all. Or to catch up on classic literature or films … or even to shower, shave, or brush my teeth. I’m quarantined in the house with my wife, our two kids, and my parents, so certainly there’s been plenty of family time, although my 7-year-daughter would inexplicably rather play fashion games on her iPad than get personalized math lessons from the author of Quantum Computing Since Democritus.

Mostly, it seems, I’ve been spending the time sleeping. Or curled up in bed, phone to face, transfixed by the disaster movie that’s the world’s new reality. Have you ever had one of those nightmares where you know the catastrophe is approaching—whether that means a missed flight, a botched presentation at your old high school, or (perhaps) more people dying than in any event since WWII—but you don’t know exactly when, and you can do nothing to avert it? Yeah, that feeling is what I now close my eyes to escape. And then I wake up, and I’m back in bizarro-nightmare-land, where the US is in no rush whatsoever to test people or to build ventilators or hospitals to cope with the coming deluge, and where ideas that could save millions have no chance against rotting institutions.

If nothing else, I guess we now have a decisive answer to the question of why humanity can’t get its act together on climate change. Namely, if we can’t wrap our heads around a catastrophe that explodes exponentially over a few weeks—if those who denied or minimized it face no consequences even when they’re dramatically refuted before everyone’s eyes—then what chance could we possibly have against a catastrophe that explodes exponentially over a century? (Note that I reject the view that the virus was sent by some guardian angel as the only possible solution to climate change, one crisis cancelling another one. For one thing, I expect emissions to roar back as soon as this new Black Death is over; for another, the virus punishes public transportation but not cars.)

Anyway, I realized I needed something, not necessarily to take my mind off the crisis, but to break me out of an unproductive spiral. Also, what better time than the present for things that I wouldn’t normally have time for? So, continuing a tradition from 2008, 2009, 2011, 2013, 2015, and 2018, we’re going to do an Ask Me Anything session. Questions directly or tangentially related to the crisis (continuing the discussion from the previous thread) are okay, questions totally unrelated to the crisis are even okayer, goofball questions are great, and questions that I can involve my two kids in answering are greatest of all. Here are this year’s ground rules:

  • 24 hours or until I get bored
  • One question per person total
  • Absolutely no multi-part questions
  • Self-contained questions only—nothing that requires me to read a paper, watch a video, etc.
  • Scan the previous AMAs to see if your question is already there
  • Any sufficiently patronizing, hostile, or annoying questions might be left in the moderation queue, 100% at my discretion

So ask away! And always look on the bright side of life.

Update (March 19): No more questions, please. Thanks, everyone! It will take me a few days just to work through all the great questions that are already in the queue.

Update (March 24): Thanks again for the 90-odd questions! For your reading convenience, here are links to all my answers, with some answers that I’m happy with bolded.

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Posted in Ask Me Anything | 322 Comments »

First it came for Wuhan

March 12th, 2020

Update (March 13): One day after I put up this post—a post that many commenters criticized as too alarmist—the first covid cases were detected in Austin. As a result, UT Austin closed its campus (including my son’s daycare), and at 3:30am, the Austin Independent School District announced its decision to suspend all schools until further notice. All my remaining plans for the semester (including visits to Berkeley, Stanford, Harvard, CU Boulder, Fermilab, Yale, and CMU) are obviously cancelled. My family is now on lockdown, in our house, probably at least until the summer. The war on the virus has reached us. The “1939” analogy that I mentioned in the post turned out to be more precise than I thought: then, as now, there were intense debates about how just serious the crisis would be, but those debates never even had a chance to get settled by argument; events on the ground simply rendered them irrelevant.

Scott’s foreword: This week Steve Ebin, a longtime Shtetl-Optimized reader (and occasional commenter) from the San Francisco tech world, sent me the essay below. Steve’s essay fit too well with my own recent thoughts, and indeed with this blog’s title, for me not to offer to share it here—and to my surprise and gratitude, Steve agreed.

I guess there are only two things I’d add to what Steve wrote. First, some commenters took me to task for a misplaced emphasis in my last coronavirus post, and on further reflection, I now concede that they were right. When a preventable catastrophe strikes the world, what’s always terrified me most are not the ranting lunatics and conspiracy theorists, even if some of those lunatics actually managed to attain the height of power, from where they played a central role in the catastrophe. No, what’s terrified me more are the blank-faced bureaucrats who’ve signed the paperwork that amounted to death warrants. Like, for example, the state regulators who ordered the Seattle infectious disease expert to stop, after she’d had enough of the government’s failure to allow corona tests, took it upon herself to start testing anyway, and found lots of positive results. Notably, only some countries have empowered lunatics, but the blank-faced bureaucrats rule everywhere unless something stronger overrides them.

Second, I’ll forever ask myself what went wrong with me, that it took me until metaphorical 1939 to acknowledge the scale of an unfolding catastrophe (on more than a purely intellectual level)—even while others were trying to tell me way back in metaphorical 1933. Even so, better metaphorical 1939 than metaphorical 1946.

Without further ado, Steve’s essay:

The most expensive meal I ever ate was in San Francisco at a restaurant called Eight Tables. As the name implies, the restaurant has only eight tables. The meal cost $1,000 and featured 12 courses, prepared by award-winning chefs.

The most expensive meal a person ever ate was in late 2019, in China, and consisted of under-cooked bat meat. It cost trillions of dollars. The person who ate it, possibly a peasant, changed the course of the 21st century. The bat he ate contained a virus, and the virus threatened to spread from this man to the rest of humanity.

I’m making up some details, of course. Maybe the man wasn’t a peasant. Or he could have been a woman. Or the bat could have been a pangolin. Or maybe, through a lucky accident (the guy was a loner perhaps), it could have not spread. That could have happened, but it didn’t. Or maybe sometimes that does happen and we don’t know it. These are just accidents of history.

I’m writing this on March 9, 2020. The good news is that the virus, in its current form, doesn’t kill children. I am so thankful for that. The bad news is that the virus does kill adults. The virus is like a grim reaper, culling the sick, the debilitated, and the elderly from the population. It attacks the pulmonary system. I heard a 25-year-old survivor describing how he became unable to control his breathing and could not fall asleep or he would die. Even for healthy young people, the prognosis is often poor. 

There were Jews in Europe in the 1930s who sat around tables with the elders of their families and villages and debated whether to leave for America, or Palestine, or South America. Most of them, including my grandmother’s family, didn’t leave, and were largely exterminated. The virus of the time was Nazism, and it too attacked the pulmonary systems of the old and the debilitated, in that case with poisonous gasses.

When you grow up as I did, you are taught to have a paranoia in the back of your mind that there is a major disaster about to happen. That a holocaust, or something of that magnitude, might occur in your lifetime. And so you are never complacent. For your whole life, you’re looking and waiting for a history changing event. You try to ensure that you are willing to follow your thoughts to their logical conclusion and take the necessary actions as a result, unlike many of the Jews of 1930s Europe, who refused to confront the obstacle in front of them until it was too late, and unlike many politicians and world leaders today, who are doing the same.

And the conclusion we must now confront is clear. We are watching a once-in-a-century event unfold. Coronavirus–its mutations, its spawn–will change the course of human history. It will overwhelm our defense system and may kill millions. It may continue to mutate and kill millions more. We will develop painful social measures to slow its spread. We will produce vaccines and better treatment protocols. Some of this will help, but none of this will work perfectly. What will happen to society as this unfolds?

My favorite biblical verse comes from Ecclesiastes: To everything there is a season, and a time to every purpose under the heaven. A time to be born, and a time to die. A time to plant and a time to pluck that which is planted. And so on.

The season has changed, and the seven years of famine have begun.

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Posted in Rage Against Doofosity, The Fate of Humanity | 169 Comments »

National disgrace

March 10th, 2020

In this blog’s now 15-year-history, at Waterloo and then MIT and now UT Austin, I’ve tried to make it clear that I blog always as Scott, never as Dr. Aaronson of Such-and-Such Institution. (God knows I’ve written a few things that a prudent dean might prefer that I hadn’t—though if I couldn’t honestly say that, in what sense would I even enjoy “academic freedom”?) Today, though, for only about the second time, I’m also writing as a professor motivated by a duty of care toward his students.

A week ago, most of my grad students were in the Bay Area for a workshop; they then returned and spent a week hanging around the CS building like normal. Yesterday I learned that at least one of those students developed symptoms consistent with covid19. Of course, it’s much more likely to be a boring cold or flu—but still, in any sane regime, just to be certain, such a person would promptly get tested.

After quarantining himself, my student called the “24/7 covid19 hotline” listed in an email from the university’s president, but found no one answering the phone over the weekend. Yesterday he finally got through—only to be told, flatly, that he couldn’t be tested due to insufficient capacity. When I heard this, I asked my department chair and dean to look into the matter, and received confirmation that yeah, it sucks, but this is the situation.

If it’s true that, as I’ve read, the same story is currently playing itself out all over the country, then this presumably isn’t the fault of anyone in UT’s health service or the city of Austin. Rather, as they say in the movies, it goes all the way to the top, to the CDC director and ultimately the president—or rather, to the festering wound that now sits where the top used to be.

Speaking of movies, over the weekend Dana and I watched Contagion, as apparently many people are now doing.  I confess that I’d missed it when it came out in 2011.  I think it’s a cinematic masterpiece.  It freely violates many of the rules of movie narrative: characters are neither done in by their own hubris, nor saved by their faith or by being A-list stars.  But Contagion is also more than a glorified public service announcement about the importance of washing your hands.  It wants to show you the reality of the human world of its characters, and also the reality of a virus, and how the two realities affect each other despite obeying utterly different logic.  It will show a scene that’s important to the charaters for human reasons, and then it will show you the same scene again, except this time making you focus on whose hand touched which surface in which order.

But for all its excellence and now-obvious prescience, there are two respects in which Contagion failed to predict the reality of 2020.  The first is just a lucky throw of the RNA dice: namely, that the real coronavirus is perhaps an order of magnitude less fatal than the movie virus, and for some unknown reason it spares children.  But the second difference is terrifying.  All the public health authorities in the movie are ultra-empowered and competent.  They do badass things like injecting themselves with experimental vaccines.  If they stumble, it’s only in deeply understandable ways that any of us might (e.g., warning their own loved ones to evacuate a city before warning the public).

In other words, when the scriptwriters, writing their disaster movie, tried to imagine the worst, they failed to imagine a US government that would essentially abandon the public, by

(1) botching a simple test that dozens of other countries performed without issue,
(2) preventing anyone else from performing their own tests, and then
(3) turning around and using the lack of positive test results to justify its own inaction.

They failed to imagine a CDC that might as well not exist for all it would do in its hour of need: one that didn’t even bother to update its website on weekends, and stopped publishing data once the data became too embarrassing.  The scriptwriters did imagine a troll gleefully spreading lies about the virus online, endangering anyone who listened to him.  They failed to imagine a universe where that troll was the president.

“I mean, don’t get me wrong,” they told me. “Trump is a racist con artist, a demagogue, the precise thing that Adams and Hamilton and Franklin tried to engineer our republic to avoid. Just, don’t get so depressed about it all the time! Moaning about how we’re trapped in a freakishly horrible branch of the wavefunction, blah blah. I mean look on the bright side! What an incredible run of luck we’ve had, that we elected a president with the mental horizons of a sadistic toddler, and yet in three years he hasn’t caused even one apocalypse. You’re alive and healthy, your loved ones are alive and healthy. It could be a lot worse!”

The above, I suspect, is a sentiment that will now forever date any writing containing it to January 2020 or earlier.

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Posted in Adventures in Meatspace, Rage Against Doofosity, The Fate of Humanity | 87 Comments »

Coronavirus: the second-weirdest solution?

March 6th, 2020

Many people have suggested coating handles, doorknobs and so forth with virus-killing copper tape. It’s a shame that this isn’t being tried on a wider scale. In the meantime, though, here’s a related but different idea that I had last night.

Imagine we could coat every doorknob, every light switch, every railing, every other surface that people might touch in public buildings, with some long-lasting disgusting, sticky, slimy substance. For a variety of reasons, one probably wouldn’t use actual excrement, although it wouldn’t hurt if the substance looked like that. Or it could be a sickly neon green or red, to make it impossible to conceal when you’d gotten the substance on your hands.

What would be the result? Of course, people would avoid touching these surfaces. If they had to, they’d do so with a napkin or glove whenever possible. If they had to touch them bare-handedly, they’d rush to wash their hands with soap as soon as possible afterwards. Certainly they wouldn’t touch their faces before having washed their hands.

In short, they’d show exactly the behaviors that experts agree are among the most helpful, if our goal is to slow the spread of the coronavirus. In effect, we’d be plugging an unfortunate gap in our evolutionary programming—namely, that the surfaces where viruses can thrive aren’t intuitively disgusting to us, as (say) vomit or putrid meat are—by making those surfaces disgusting, as they ought to be in the middle of a pandemic.

Note that, even if it somehow turns out to be infeasible to coat all the touchable surfaces in public buildings with disgusting goo, you might still derive great personal benefit from imagining them so covered. If you manage to pull that off, it will yield just the right heuristic for when and how often you should now be washing your hands (and avoiding touching your face), without no need for additional conscious reflection.

Mostly, having the above thoughts made me grateful for my friend Robin Hanson. For as long Robin is around, tweeting and blogging from his unique corner of mindspace, no one will ever be able to say that my ideas for how to control the coronavirus were the world’s weirdest or most politically tone-deaf.

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Posted in Embarrassing Myself, Procrastination, The Fate of Humanity | 46 Comments »

Turn down the quantum volume

March 5th, 2020

Several people asked me to comment on the recent announcement by Honeywell that they’ll soon have what they call “the most powerful” quantum computer (see here for press release, here for Forbes article, here for paper).

I’m glad that Honeywell, which many people might know as an air-conditioner manufacturer, has entered the race for trapped-ion QC. I wish them success. I’ve known about what they were doing in part because Drew Potter, my friend and colleague in UT Austin’s physics department, took a one-year leave from UT to contribute to their effort.

Here I wanted to comment about one detail in Honeywell’s announcement: namely, the huge emphasis on “quantum volume” as the central metric for judging quantum computing progress, and the basis for calling their own planned device the “most powerful.” One journalist asked me to explain why quantum volume is such an important measure. I had to give her an honest answer: I don’t know whether it is.

Quantum volume was invented a few years ago by a group at IBM. According to one of their papers, it can be defined roughly as 2k, where k is the largest number such that you can run a k-qubit random quantum circuit, with depth k and with any-to-any connectivity, and have at least (say) 2/3 probability of measuring an answer that passes some statistical test. (In the paper, they use what Lijie Chen and I named Heavy Output Generation, though Google’s Linear Cross-Entropy Benchmark is similar.)

I don’t know why IBM takes the “volume” to be 2k rather than k itself. Leaving that aside, though, the idea was to invent a single “goodness measure” for quantum computers that can’t be gamed either by building a huge number of qubits that don’t maintain nearly enough coherence (what one might call “the D-Wave approach”), or by building just one perfect qubit, or by building qubits that behave well in isolation but don’t interact easily. Note that the any-to-any connectivity requirement makes things harder for architectures with nearest-neighbor interactions only, like the 2D superconducting chips being built by Google, Rigetti, or IBM itself.

You know the notion of a researcher’s h-index—defined as the largest h such that she’s published h papers that garnered h citations each? Quantum volume is basically an h-index for quantum computers. It’s an attempt to take several different yardsticks of experimental progress, none terribly useful in isolation, and combine them into one “consumer index.”

Certainly I sympathize with the goal of broadening people’s focus beyond the “but how many qubits does it have?” question—since the answer to that question is meaningless without further information about what the qubits can do. From that standpoint, quantum volume seems like a clear step in the right direction.

Alas, Goodhart’s Law states that “as soon as a measure becomes a target, it ceases to be a good measure.” That happened years ago with the h-index, which now regularly pollutes academic hiring and promotion decisions, to the point where its inventor expressed regrets. Quantum volume is now looking to me like another example of Goodhart’s Law at work.

The position of Honeywell’s PR seems to be that, if they can build a device that can apply 6 layers of gates to 6 qubits, with full connectivity and good fidelity, that will then count as “the world’s most powerful quantum computer,” since it will have the largest volume. One problem here is that such a device could be simulated by maintaining a vector of only 26=64 amplitudes. This is nowhere near quantum supremacy (i.e., beating classical computers at some well-defined task), which is a necessary though not sufficient condition for doing anything useful.

Think of a university that achieves an average faculty-to-student ratio of infinity by holding one class with zero students. It gets the “best score” only by exploiting an obvious defect in the scoring system.

So what’s the alternative? The policy I prefer is simply to tell the world all your system specs, as clearly as you can, with no attempts made to bury the lede. How many qubits do you have? With what coherence times? With what connectivity? What are the 1- and 2-qubit gate fidelities? What depth of circuit can you do? What resources do the standard classical algorithms need to simulate your system? Most importantly: what’s the main drawback of your system, the spec that’s the worst, the one you most need to improve? What prevents you from having a scalable quantum computer right now? And are you going to tell me, or will you make me scour Appendix III.B in your paper, or worse yet, ask one of your competitors?

I confess that the answers to the above questions are hard to summarize in a single number (unless you, like, concatenated binary encodings of them or something). But they can be ineffably combined, to produce a progress metric that one of my postdocs suggested calling “quantum scottness,” and which roughly equals the number of expressions of wide-eyed surprise minus the number of groans.

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Posted in Quantum | 36 Comments »

A coronavirus poem

March 3rd, 2020

These next few months, every time I stop myself from touching my face by force of will,

Let me remind myself that the same willpower is available to diet, to exercise, to throw myself into a project, to keep calm amid screaming, to introduce myself to strangers, to decrease the fraction of my life spent getting upset that someone was mean to my ingroup on social media, or otherwise to better myself as a human specimen.

Yea, let all of these things be just as easy for me as it was not to touch my face.

Ah, but what if I forget, what if I do keep touching my face in the next few months?

In one plausible scenario, with at least ~0.1% probability and probably higher depending on my age, a cheap answer will be available to that question: namely, that I’ll no longer be around to ponder the implications.

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Posted in Embarrassing Myself, Nerd Self-Help, The Fate of Humanity | 12 Comments »

Paperz

March 3rd, 2020

Soon, all anyone will want to talk about is quarantines, food shortages, N95 masks, the suspension of universities and of scientific conferences. (As many others have pointed out, this last might actually be a boon to scientific productivity—as it was for a young Isaac Newton when Cambridge was closed for the bubonic plague, so Newton went home and invented calculus and mechanics.)

Anyway, before that all happens, I figured I’d get in a last post about quantum information and complexity theory progress.

Hsin-Yuan Huang, Richard Kueng, and John Preskill have a nice preprint entitled Predicting Many Properties of a Quantum System from Very Few Measurements. In it they take shadow tomography, which I proposed a couple years ago, and try to bring it closer to practicality on near-term devices, by restricting to the special case of non-adaptive, one-shot measurements, on separate copies of the state ρ that you’re trying to learn about. They show that this is possible using a number of copies that depends logarithmically on the number of properties you’re trying to learn (the optimal dependence), not at all on the Hilbert space dimension, and linearly on a new “shadow norm” quantity that they introduce.

Rahul Ilango, Bruno Loff, and Igor Oliveira announced the pretty spectacular-sounding result that the Minimum Circuit Size Problem (MCSP) is NP-complete for multi-output functions—that is, for Boolean functions f with not only many input bits but many outputs. Given the 2n-sized truth table of a Boolean function f:{0,1}n→{0,1}, the original MCSP simply asks for the size of the smallest Boolean circuit that computes f. This problem was studied in the USSR as early as the 1950s; whether it’s NP-complete has stood for decades as one of the big open problems of complexity theory. We’ve known that if you could quickly solve MCSP then you could also invert any one-way function, but we’ve also known technical barriers to going beyond that to a flat-out NP-hardness result, at least via known routes. Before seeing this paper, I’d never thought about whether MCSP for many-output functions might somehow be easier to classify, but apparently it is!

Hamoon Mousavi, Seyed Nezhadi, and Henry Yuen have now taken the MIP*=RE breakthrough even a tiny step further, by showing that “zero-gap MIP*” (that is, quantum multi-prover interactive proofs with an arbitrarily small gap between the completeness and soundness probabilities) takes you even beyond the halting problem (i.e., beyond Recursively Enumerable or RE), and up to the second level of the arithmetical hierarchy (i.e., to the halting problem for Turing machines with oracles for the original halting problem). This answers a question that someone asked in the comments section of this blog.

Several people asked me for comment on the paper What limits the simulation of quantum computers?, by Yiqing Zhou, Miles Stoudenmire, and Xavier Waintal. In particular, does this paper refute or weaken Google’s quantum supremacy claim, as the paper does not claim to do (but, rather coyly, also does not claim not to do)? Short answer: No, it doesn’t, or not now anyway.

Longer, more technical answer: The quoted simulation times, just a few minutes for quantum circuits with 54 qubits and depth 20, assume Controlled-Z gates rather than iSWAP-like gates. Using tensor network methods, the classical simulation cost with the former is roughly the square root of the simulation cost with the latter (~2k versus ~4k for some parameter k related to the depth). As it happens, Google switched its hardware from Controlled-Z to iSWAP-like gates a couple years ago precisely because they realized this—I had a conversation about it with Sergio Boixo at the time. Once this issue is accounted for, the quoted simulation times in the new paper seem to be roughly in line with what was previously reported by, e.g., Johnnie Gray and Google itself.

Oh yeah, I enjoyed Quantum Homeopathy Works. Cool result, and the title is actually a pretty accurate description of the contents.

To end with a community announcement: as many of you might know, the American Physical Society’s March Meeting, which was planned for this week in Denver, was abruptly cancelled due to the coronavirus (leaving thousands of physicists out their flights and hotel rooms—many had even already arrived there). However, my colleague Michael Biercuk kindly alerted me to a “virtual March Meeting” that’s been set up online, with recorded talks and live webinars. Even after the pandemic passes, is this a model that we should increasingly move to? I wouldn’t have thought so ten or fifteen years ago, but today every schlep across the continent brings me a step closer to shouting “yes”…

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Posted in Complexity, Quantum | 12 Comments »

Freeman Dyson and Boris Tsirelson

February 29th, 2020

Today, as the world braces for the possibility of losing millions of lives to the new coronavirus—to the hunger for pangolin meat, of all things (combined with the evisceration of competent public health agencies like the CDC)—we also mourn the loss of two incredibly special lives, those of Freeman Dyson (age 96) and Boris Tsirelson (age 69).

Freeman Dyson was sufficiently legendary, both within and beyond the worlds of math and physics, that there’s very little I can add to what’s been said. It seemed like he was immortal, although I’d heard from mutual friends that his health was failing over the past year. When I spent a year as a postdoc at the Institute for Advanced Study, in 2004-5, I often sat across from Dyson in the common room, while he drank tea and read the news. That I never once struck up a conversation with him is a regret that I’ll now carry with me forever.

My only exchange with Dyson came when he gave a lecture at UC Berkeley, about how life might persist infinitely far into the future, even after the last stars had burnt out, by feeding off steadily dimishing negentropy flows in the nearly-thermal radiation. During the Q&A, I challenged Dyson that his proposal seemed to assume an analog model of computation. But, I asked, once we took on board the quantum-gravity insights of Jacob Bekenstein and others, suggesting that nature behaves like a (quantum) digital computer at the Planck scale, with at most ~1043 operations per second and ~1069 qubits per square meter and so forth, wasn’t this sort of proposal ruled out? “I’m not going to argue with you,” was Dyson’s response. Yes, he’d assumed an analog computational model; if computation was digital then that surely changed the picture.

Sometimes—and not just with his climate skepticism, but also (e.g.) with his idea that general relativity and quantum mechanics didn’t need to be reconciled, that it was totally fine for the deepest layer of reality to be a patchwork of inconsistent theories—Dyson’s views struck me as not merely contrarian but as a high-level form of trolling. Even so, Dyson’s book Disturbing the Universe had had a major impact on me as a teenager, for the sparkling prose as much as for the ideas.

With Dyson’s passing, the scientific world has lost one of its last direct links to a heroic era, of Einstein and Oppenheimer and von Neumann and a young Richard Feynman, when theoretical physics stood at the helm of civilization like never before or since. Dyson, who apparently remained not only lucid but mathematically powerful (!) well into his last year, clearly remembered when the Golden Age of science fiction looked like simply sober forecasting; when the smartest young people, rather than denouncing each other on Twitter, dreamed of scouting the solar system in thermonuclear-explosion-powered spacecraft and seriously worked to make that happen.

Boris Tsirelson (homepage, Wikipedia), who emigrated from the Soviet Union and then worked at Tel Aviv University (where my wife Dana attended his math lectures), wasn’t nearly as well known as Dyson to the wider world, but was equally beloved within the quantum computing and information community. Tsirelson’s bound, which he proved in the 1980s, showed that even quantum mechanics could only violate the Bell inequality by so much and by no more, could only let Alice and Bob win the CHSH game with probability cos2(π/8). This seminal result anticipated many of the questions that would only be asked decades later with the rise of quantum information. Tsirelson’s investigations of quantum nonlocality also led him to pose the famous Tsirelson’s problem: loosely speaking, can all sets of quantum correlations that can arise from an infinite amount of entanglement, be arbitrarily well approximated using finite amounts of entanglement? The spectacular answer—no—was only announced one month ago, as a corollary of the MIP*=RE breakthrough, something that Tsirelson happily lived to see although I don’t know what his reaction was (update: I’m told that he indeed learned of it in his final weeks, and was happy about it). Sadly, for some reason, I never met Tsirelson in person, although I did have lively email exchanges with him 10-15 years ago about his problem and other topics. This amusing interview with Tsirelson gives some sense for his personality (hat tip to Gil Kalai, who knew Tsirelson well).

Please share any memories of Dyson or Tsirelson in the comments section.

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Posted in Announcements, Nerd Interest, Quantum, The Fate of Humanity | 40 Comments »

My video interview with Lex Fridman at MIT about philosophy and quantum computing

February 17th, 2020

Here it is (about 90 minutes; I recommend the 1.5x speed)

I had buried this as an addendum to my previous post on the quantum supremacy lecture tour, but then decided that a steely-eyed assessment of what’s likely to have more or less interest for this blog’s readers probably militated in favor of a separate post.

Thanks so much to Lex for arranging the interview and for his questions!

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Posted in Adventures in Meatspace, Announcements, Metaphysical Spouting, Quantum | 85 Comments »

My “Quantum Supremacy: Skeptics Were Wrong” 2020 World Speaking Tour

February 17th, 2020

(At a few people’s request, I’ve changed the title so that it no longer refers to a specific person. I try always to be accurate, amusing, and appropriate, but sometimes I only hit 1 or 2 of the 3.)

As part of my speaking tour, in the last month I’ve already given talks at the following fine places:

World Economic Forum at Davos
University of Waterloo
Perimeter Institute
UC Berkeley
Harvard
MIT
Princeton
University of Houston

And I’ll be giving talks at the following places over the next couple of months:

Louisiana State University
Pittsburgh Quantum Institute
Fermilab
Yale

For anyone who’s interested, I’ll add links and dates to this post later (if you want that to happen any faster, feel free to hunt them down for me!).

In the meantime, there are also interviews! See, for example, this 5-minute one on Texas Standard (an NPR affiliate), where I’m asked about the current state of quantum computing in the US, in light of the Trump administration’s recent proposal to give a big boost to quantum computing and AI research, even while slashing and burning basic science more broadly. I made some critical comments—for example, about the need to support the whole basic research ecosystem (I pointed out that “quantum computing can’t thrive in isolation”), and also about the urgent need to make it feasible for the best researchers from around the world to get US visas and green cards. Unfortunately, those parts seem to have been edited out, in favor of my explanations of basic points about quantum computing.

More Updates:

There was a discussion on Twitter of the ethics of the “Quantum Bullshit Detector” Twitter feed—which dishes out vigilante justice, like some dark and troubled comic-book hero, by rendering anonymous, unexplained, unaccountable, very often correct albeit not infallible verdicts of “Bullshit” or “Not Bullshit” on claimed quantum information advances. As part of that discussion, Christopher Savoie wrote:

[Criticizing] is what we do in science. [But not calling] “bullshit” anonymously and without any accountability. Look at Scott Aaronson’s blog. He takes strong positions. But as Scott. I respect that.

What do people think: should “He takes strong positions. But as Scott.” be added onto the Shtetl-Optimized header bar?

In other news, I was amused by the following headline, for a Vice story about the MIP*=RE breakthrough: Mathematicians Are Studying Planet-Sized Supercomputers With God-Like Powers. (If I’m going to quibble about accuracy: only planet-sized???)

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Posted in Adventures in Meatspace, Announcements, Quantum | 59 Comments »

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