Quantum Computing Since Democritus: The Buzz Intensifies

Update (March 22): The Kindle edition of Quantum Computing Since Democritus is now available, for the low price of $15.40!  (Not factorial.)  Click here to get it from amazon.com, or here to get it from amazon.co.uk.  And let me know how it looks (I haven’t seen it yet).  Another Update: Just saw the Kindle edition, and the figures and formulas came out great!  It’s a product I stand behind with pride.

In the meantime, I regret to say that the marketing for this book is getting crasser and more exploitative by the day.



It seems like wherever I go these days, all anyone wants to talk about is Quantum Computing Since Democritus—the sprawling new book by Scott Aaronson, published by Cambridge University Press and available for order now.  Among leading figures in quantum information science—many of them well-known to Shtetl-Optimized readers—the book is garnering the sort of hyperbolic praise that would make Shakespeare or Tolstoy blush:

“I laughed, I cried, I fell off my chair – and that was just reading the chapter on Computational Complexity.  Aaronson is a tornado of intellectual activity: he rips our brains from their intellectual foundations; twists them through a tour of physics, mathematics, computer science, and philosophy; stuffs them full of facts and theorems; tickles them until they cry ‘Uncle’; and then drops them, quivering, back into our skulls.  Aaronson raises deep questions of how the physical universe is put together and why it is put together the way it is.  While we read his lucid explanations we can believe – at least while we hold the book in our hands – that we understand the answers, too.” —Seth Lloyd

“Scott Aaronson has written a beautiful and highly original synthesis of what we know about some of the most fundamental questions in science: What is information? What does it mean to compute? What is the nature of mind and of free will?” —Michael Nielsen

“Not since Richard Feynman’s Lectures on Physics has there been a set of lecture notes as brilliant and as entertaining.  Aaronson leads the reader on a wild romp through the most important intellectual achievements in computing and physics, weaving these seemingly disparate fields into a captivating narrative for our modern age of information.  Aaronson wildly runs through the fields of physics and computers, showing us how they are connected, how to understand our computational universe, and what questions exist on the borders of these fields that we still don’t understand.   This book is a poem disguised as a set of lecture notes.  The lectures are on computing and physics, complexity theory and mathematical logic and quantum physics.  The poem is made up of proofs, jokes, stories, and revelations, synthesizing the two towering fields of computer science and physics into a coherent tapestry of sheer intellectual awesomeness.” —Dave Bacon

After months of overhearing people saying things like the above—in the halls of MIT, the checkout line at Trader Joe’s, the bathroom, anywhere—I finally had to ask in annoyance: “is all this buzz justified?  I mean, I’m sure the book is as deep, hilarious, and worldview-changing as everyone says it is.  But, after all, it’s based off lecture notes that have long been available for free on the web.  And Aaronson, being the magnanimous, open-access-loving saint that he is, has no plans to remove the online notes, even though he could really use the royalties from book sales to feed his growing family.  Nor does Cambridge University Press object to his principled decision.”

“No, you don’t understand,” they told me.  “Word on the street has it that the book is extensively updated for 2013—that it’s packed with new discussions of things like algebrization, lattice-based cryptography, the QIP=PSPACE theorem, the ‘quantum time travel controversy,’ BosonSampling, black-hole firewalls, and even the Australian models episode.  They say it took years of painstaking work, by Aaronson and his student Alex Arkhipov, to get the notes into book form: fixing mistakes, clarifying difficult points, smoothing out rough edges, all while leaving intact the original’s inimitable humor.  I even heard Aaronson reveals he’s changed his mind about certain things since 2006.  How could you not want such a labor of love on your bookshelf?”

Exasperated, I finally exclaimed: “But the book isn’t even out yet in North America!  Amazon.com says it won’t ship until April 30.”

“Sure,” one gas-station attendant replied to me, “but the secret is, it’s available now from Amazon.co.uk.  Personally, I couldn’t wait a month, so I ordered it shipped to me from across the pond.  But if you’re a less hardcore quantum complexity theory fan, and you live in North America, you can also preorder the book from Amazon.com, and they’ll send it to you when it arrives.”

Much as the hype still grated, I had to admit that I’d run out of counterarguments, so I looked into ordering a copy for myself.

70 Responses to “Quantum Computing Since Democritus: The Buzz Intensifies”

  1. Jeffrey Scofield Says:

    As I promised years ago, I’m ordering one copy for each of my two young sons. Not since the Feynman Lectures has there been a book so appropriate for bedtime reading yet also for carrying off to college in one’s satchel.

  2. joe Says:

    Fix your Amazon links! So many book sales squelched by the dreaded 404…

  3. Matt Leifer Says:

    Will there be an ebook?

  4. Scott Says:

    Thanks so much, Jeffrey! Hope they like it.

  5. Scott Says:

    joe #2: Argh, thanks, fixed! (They were missing http://'s)

  6. Scott Says:

    Matt Leifer #3: Yes, CUP says they’re planning to do a Kindle edition, but I don’t know the timetable for that.

  7. Gus Says:

    Congratulations, Scott. I look forward to all the updated nuggets in the printed version.

    Regarding the lack of e-book thus far: what’s up with that?! Even if one is not concerned about the environmental degradation associated with printing physical books and then shipping them across an ocean, the sheer waste of resources (from a purely economic perspective) is enough to make one’s skin crawl. Did you try to pressure CUP on this issue?

    Some questions I’ve always wanted to ask authors of books of this type, but never had the nerve until your book came along: Do you expect the royalties to be significant enough that you simply could not afford to make the book freely available? Is your first priority to make money, or to be read by as wide an audience as possible? If the latter, do you think that a non-free book marketed by a publisher will reach a wider audience than a relatively un-marketed free book on the internet? I ask these questions in all seriousness. Naturally, they are personal questions and I will not be offended if you decline to answer.

    Say hi to Lily for me. 🙂

  8. Scott Says:

    Gus #7: Yes, I did tell my editor at CUP that I wanted a Kindle version out as soon as possible. I don’t know the status of it, and (prompted by your question) I think I’ll check again. But I do know that e-books can be nontrivial to get right, especially when (like this one) they have huge numbers of displayed formulas and nonstandard symbols.

    Now, regarding your other questions:

    1. I have made a draft freely available on the web, and I intend to keep it there. That’s more than probably >99% of authors do, even today. Don’t I get any credit for that? 🙂

    (In particular, this seemed like a way to have a decently-selling book, while still probably causing zero net harm to the goal of reaching the largest possible audience. Sure, maybe there are a few people who would read a free book, but will read neither a non-free book nor the free draft. But believe it or not, there are also people who will read a traditional book, and won’t read what they consider “random stuff on the web.”)

    2. Speaking of which, some people actually like reading printed books, and I count myself as one of them. (Though I’ve also started to like e-books, as they have obvious convenience benefits that compensate for not being able to see where you are by hefting the pages with your fingers.)

    3. My royalties are somewhere between $1 and $2 per book. If we sell 5,000 copies, that’s barely enough to be worth discussing. If we sell 500,000 copies, it’s enough to put Lily through college, and pay off both Vinay Deolalikar and Robert Alicki in the unlikely event that becomes necessary. I don’t know what to expect, but figured it couldn’t hurt to try and increase the probability of the latter. 🙂

    4. Is making money my first priority? Ask yourself: if it were, would I have written Quantum Computing Since Democritus, or Shed Those Pounds The BQP Way?

    5. Sure, shipping books across an ocean harms the environment. So does shipping yourself to a conference (as you and I both do), having kids, and almost every other human activity. After years of reflecting on this, I eventually decided the best response was not that the relatively few people who care about such things should unilaterally join monasteries (while the rest of the world continues happily driving SUVs and buying printed copies of Harry Potter and the Fifty Shades of Grey), but rather that they should work toward a future where all economic activities are simply taxed at a rate commensurate with the environmental damage they do.

  9. John Says:

    “Shed Those Pounds The BQP Way”

    OMG, I so want this book!!!

  10. Moritz Says:

    Also the very first link seems to be broken.

  11. asdf Says:

    Congrats, Scott. I’ll snag a printed copy when I can. I won’t go anywhere near a Kindle edition because of the usual eeeeevil DRM issues.

    Meanwhile, here’s a couple of good CUP books available as authorized pdf’s:



    I have printed and electronic copies of both, and they’re both great. The second one despite being titled “information theory” etc., actually (among other things) has a lot of well written info about error correcting codes.

  12. Vladimir Says:

    (The first link to the CUP site is still broken.)

  13. Jay Says:

    It is understandable that you need to feed your family, but I am disappointed you feel obliged to appear half naked on the cover.

  14. Jay Says:

    ( Congrats 🙂 )

  15. Scott Says:

    Moritz #10, Vladimir #12: Dammit, fixed, thanks!

    Jay #13: LOL!

  16. Gus Says:

    Scott #8: Thanks for answering. Of course you get heaps of credit for putting a free draft on the internet, and I apologize for not making that clear straight away.

    I would like to ask those questions to many other authors like yourself, most of whom have not put a free draft on the web. You’re probably the only one who would answer me though. Unfortunately, you’ve corrupted my painstakingly scientific poll with n=1 by making yourself ineligible.

    I’m a little surprised that your royalties per book are so small, but I guess somebody needs to cover the cost of all those duds shipped across oceans by CUP. It must be exciting to contemplate your potential sales. I sincerely hope you strike it big!

  17. Vadim Says:

    Ugh, I can only imagine how “Shed Those Pounds The BQP Way” would get butchered in the popular press: “A book that shows how you can both lose weight and not lose weight at the same time.”

  18. John Preskill Says:

    Wow, Seth really knows how to make me want to read a book! I think my favorite part is “… and then drops them, quivering, back into our skulls.”

    Now that’s a BLURB! But it wasn’t really necessary. I’ve known I want this book since hearing about it in the bathroom at Trader Joe’s.

  19. Slipper.Mystery Says:

    Although the author may appear to spend too much time reading (and perhaps even writing) his own press reviews, if you read only one book by scott aaronson this year, definitely read this one.

  20. Clement Says:

    Out of curiosity, how accessible (i.e, newbie-friendly) is your book? I plan on buying one copy for myself, but do also have a 4 and 3-year old niece and nephew, and I’d be rather pleased to see them grow into enlightened, educated people with a strong taste for science (before of course their clubbing me to death for ruining their childhood).

  21. Scott Says:

    Clement #20: If a 3- or 4-year-old (or even a 5-year-old) can read this book, that’s definitely a kid who I want to meet! 🙂 I’m calling the book “semipopular”: it’s way too informal to be a textbook, but also goes way too deep to be an ordinary “pop-science” book. I wrote it for the much-neglected third audience of the sort of people who read this blog. In terms of level, maybe the closest comparisons I can think of are Roger Penrose’s The Road to Reality or Lenny Susskind’s The Theoretical Minimum.

  22. Clement Says:

    Thanks! I’ll stick with one for myself, then (and buy them S. Colbert’s “I Am A Pole” instead. This still can mess up with their minds.)

  23. Michael Nielsen Says:

    Congrats, Scott. I hope a zillion people read it.

    I can’t resist quoting my original (unedited by CUP) endorsement:

    “This book is a beautiful synthesis of what we know about some of the most fundamental questions in science.  What is information?  What does it mean to compute?  What is the nature of mind and of free will? Along the way, Scott Aaronson provides crisp and often highly original explanations of some of the most striking recent ideas in science, ideas such as zero-knowledge proofs, quantum computing, black hole entropy, and many others.  Highly recommended.”

  24. Rahul Says:


    Off topic but have you had a look at this latest NYT piece on QC? You are quoted in it!


    Apparantly Lockheed Martin’s embracing D-Wave’s magic box. To me that article seemed grossly over-hyped but maybe others can comment.

    Hype e.g.

    Ray Johnson, Lockheed’s chief technical officer, said his company would use the quantum computer to create and test complex radar, space and aircraft systems. It could be possible, for example, to tell instantly how the millions of lines of software running a network of satellites would react to a solar burst or a pulse from a nuclear explosion — something that can now take weeks, if ever, to determine.

  25. Mateus Araújo Says:

    Congratulations for the book, Scott. I’ll put it besides my beloved Mike & Ike =)

    But are you sure that the Kindle version does not exist? Amazon thinks it does: http://www.amazon.co.uk/Quantum-Computing-since-Democritus-ebook/dp/B00B4V6IZK/ref=tmm_kin_title_0

  26. Tim Converse Says:

    There seems to be a Kindle edition available now on amazon.com.


  27. Vadim Says:

    Awesome find, Tim, I’m reading it as I type this! Though it’s strange that Amazon’s page for the actual book indicates that there’s no Kindle version available when Amazon clearly sells the Kindle version. I guess Amazon is big enough where the left hand and right hand can’t always know what each other is doing.

  28. John Sidles Says:

    LOL … an eminent quantum theorist once confessed to me of having written considerably many popular books because they had considerably many children enrolled in [expensive] schools. Therefore Scott, please accept this wish that you and Emma (?) together have many wonderful children who happily catalyze the writing of many wonderful books!

  29. Scott Says:

    Tim Converse #26: Yes, thanks so much for the find!

  30. Scott Says:

    John Sidles #28:

      Therefore Scott, please accept this wish that you and Emma (?) together have many wonderful children who happily catalyze the writing of many wonderful books!

    Thanks! But her name is Dana. 🙂

  31. Scott Says:

    Rahul #24:

      Off topic but have you had a look at this latest NYT piece on QC? You are quoted in it!

    Yeah, I saw it this morning. The strange part is that I have zero recollection of saying the things John Markoff quotes me as saying! (I might have said them, but I don’t remember when. And it probably would’ve been in the context of how D-Wave’s communications have improved since 2007—something the article omitted, maybe because they just wanted an uncomplicated skeptic.) In any case, there seemed to be nothing really new in this article—I’m not sure why it was written.

  32. John Sidles Says:

    Scott #30 … doh! … yes, Dana’s name was recalled erroneously (hence the ?) yet the sentiment regarding future happy children catalyzing future wonderful books was entirely sincere. Best wishes for further happy conceptions of every kind!

  33. Paul Beame Says:

    Scott: In any case, there seemed to be nothing really new in this article—I’m not sure why it was written.

    I find the coincidence suspicious: Just when your book is coming out, there is Lazardis’ announcement on creating a “Quantum Valley” in Canada and then Markoff hypes quantum computing a couple of days later with the D-Wave article.

    Don’t be modest. I suspect it is all an elaborate ploy designed to increase sales of your book.

  34. JT Says:

    Paul: Don’t be modest. I suspect it is all an elaborate ploy designed to increase sales of your book.

    It’s an effective ploy. The D-Wave article is currently at the top of the NYTimes’ most-emailed list!

  35. John Preskill Says:

    Being impatient, I bought the Kindle edition. It looks good, and I am already enjoying it.

  36. Douglas Knight Says:

    How about you modify the lecture notes page to say “Now available in book form!” and link somewhere?

  37. Ajit R. Jadhav Says:

    Seth Lloyd said:

    While we read his lucid explanations we can believe – at least while we hold the book in our hands – that we understand the answers, too. [emphasis mine]

    What’s the special thing about Scott’s book that Seth Lloyd had in mind, here? … It seems to happen to me with almost any book I read.


  38. Goda Says:

    I have no doubts that this book wil be just great! Really want to read it asap!

  39. Chris Tomlinson Says:

    There is also a PDF (ADE DRM’d) version available from several online sellers: ebooks.com and booksonboard.com. I prefer PDF since the typesetting is generally cleaner than Kindle or ePub for mathematical materials.

  40. Scott Says:

    Douglas Knight #36: Thanks very much for the suggestion! Done.

  41. Gil Kalai Says:

    Congratulations, Scott, for your first book!

    (I searched Scott Aaronson in Amazon to verify that it is indeed the first, and while other amusing items came up, it seems they refer to other people with the same name.) Having the first book published is a very special feeling!

  42. Scott Says:

    Thanks, Gil!

  43. Henning Dekant Says:

    Dang it, this marketing really works, just … cannot … resist … adorable baby pics 🙂

    Interestingly, she seems to be more taken to the eBook. Probably feels all warm and comfortably heavy on the belly.

  44. Andrew Hickey Says:

    Just in case anyone was in doubt, there are epub versions available from the usual online bookstores, too, not just Kindle.

  45. Howto: Strip Adobe DRM in Debian GNU/Linux | Sci-Ence! Justice Leak! Says:

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  46. William Hird Says:

    The baby is adorable, would it be appropriate to call her “The First Baby of Computer Science” !!! 😉

  47. q vs c Says:


    does this prove quantumness has more compuatational power than from classical computing?

  48. Scott Says:

    q vs c #47: No. It looks like a very nice result, but one that has nothing to do with computational power.

  49. tubelite Says:

    FYI, I just bought the Kindle edition for $25.76 (INR 1486) from Kindle’s India store. Usually the prices there are lower there than the US Kindle store, funny…

  50. Cristopher Moore Says:

    I read your online notes when they first came out. Now I get to enjoy it all over again.

    When will the graphic novel version appear?

  51. luca turin Says:

    Great book ! I read through it once [is one even supposed to do this with a serious book ?] and understood, say, 5%, will spend the next few months working on a further 5% or so, which would be fine by me. One comment: you say that Gauss could factor large numbers in his head and maybe had/was a quantum computer but the rest of us have/are no such thing. As a biologist, my feeling is our hardware _must_ be the same as Gauss’, except that most of us use the world’s most powerful warm quantum computer to play Pong instead of during serious stuff.

  52. Lukasz Grabowski Says:

    Congratulation for the book! I thoroughly enjoyed reading the lecture notes and I’d be very glad to get you a pint by buying the e-book. Is there any chance there’s gonna be a version for other e-readers? For example epub version? Here in Europe kindle is not the only or even the default ereader…

  53. Scott Says:

    Lukasz #52: Yes, it looks like there are versions for other e-readers — please check comments #39 and #44 above.

  54. Jon Says:

    Oh wow.

    Istumbled across your PHYS771 Lecture 9 notes, and some of the related links like, “NP-complete Problems and Physical Reality” and immediately though decided to see if you had written a book.

    Imagine my delight to find out you have, in fact, and it just came last week! Kindle edition purchased and I’m going to start it tonight.

  55. Lazaridis to keep BlackBerry stake, focus on new venture | eJumo Says:

    […] his fortune to found the Perimeter Institute for Theoretical Physics in Waterloo, said he sees the quantum computing field “producing opportunities in the near-term.” He said the fund has started making […]

  56. q vs c Says:

    not to be cranky… what do you think about this? I looked at scholar.google. It has 38 citations.


  57. Totient Says:

    Finally, my favorite set of lecture notes, now in convenient e-book form! (Of course, half of my soon-to-be-graduate-student self is asking “Why did I just pay for something I can get online for free?”)

  58. GiantRobot Says:


    Congrats on the book. What’s the cover photo about?

  59. Scott Says:

    GiantRobot #58: Thanks! The cover shows a Dutch painting of Democritus from the 1600s. No one actually knows what he looked like, so the painter simply imagined it, but kept in mind that Democritus was known to his contemporaries as “the laughing philosopher.” I thought (hoped) that Democritus’s laughter captured the spirit of the book—and just as importantly, the painting was hundreds of years past its copyright expiration. 🙂

  60. Sebastian Henckel Says:

    Hi! Just bought the book on Kindle in Germany. 15.53 Euros here. Am currently at chapter 4, and stumbled over the author’s attack on “Meat chauvinism”. Well, I’m guilty for sure:

    Meat-chauvinism is necessary and righteous.

    Otherwise, the following Turing test would claim consciousness for a machine that is obviously devoid of it:

    Here’s the description of the machine and the associated Turing Test:

    Hook up a speaker with the Real part of a Riemann Zeta function generator. Normalize the output so that the speaker doesn’t blow out for high values. Hook up an analog TV set with the Imaginary part of the Riemann Zeta function generator. Also normalize that output so the TV set doesn’t blow.

    Choose a random line segment on the complex plane of length 1 parallel to the real segment [0,1]. Parametrize the line segment to be run through continuously in 100 years, from left to right. Feed this time parametrized domain segment path into the Riemann Zeta function generator and have its Riemann Zeta function values output into audio/video. The screen will flicker, the audio hum. There’s our AI machine – at least our first try.

    Now let a human being converse with this machine for 100 years at the most. (This is the maximum length the test has to work – a lifetime.) The human tester is looking at the screen, expecting a face, and listening to the audio, expecting a voice. Once the Turing test fails, i.e. the human tester determines he isn’t conversing with an intelligent being, the machine is reset and the test is restarted with a new domain. The machine has no inputs, so it does not process the information given by the human tester. It just outputs audio and video according to the Riemann Zeta function being output for the random subdomain. This is going to be very boring most of the time. But we have all the time in the world. “Conversation” wasn’t interesting? Reset! Each reset is considered a new machine. Here’s hoping next time ‘round we will have built ourselves an AI machine. When the human tester becomes too old to continue holding the test, he is replaced by another tester.

    Because the Zeta function is universal (http://en.wikipedia.org/wiki/Zeta_function_universality), eventually – albeit after a VERY long time – the tester will encounter a subdomain of the Zeta function that he will have a brilliant, heartfelt, life-lasting conversation with – A beautiful woman appears on the screen, who seems to understand every nuance of his feelings, questions and concerns. They will grow old together and die as a happy couple. Turing passed with flying colours. I ask: Does this machine qualify for having consciousness? No? Well, who are you to deny a soul to this domain of the Zeta function, you racist, meat-chauvinist pigs!

    And don’t tell me the machine flunked too often before – those were different machines!

  61. Joe Shipman Says:


    I bought the book on Kindle and read it (it cost $18.56 not $15.40 but it was worth it anyway).

    Three points, which I may or may not have made in coments here before:

    1) If the fine-structure constant, or any other dimensionless physically measurable number, is not Turing-computable as a real number, then the ordinary Church-Turing thesis is false, and so is the extended Church-Turing thesis. These numbers are polynomial-time equivalent to measurable probabilities, and although the first N bits of such a probability takes exponentially long to measure (asymptotically, you need (4+delta)^N trials in order to have a probability of (1-epsilon) of never getting a bit wrong), you can create an exponentially “padded” version of the number which is still noncomputable classically but is computable in BQP* (a generalized version of BQP that allows us to count experiments measuring these probabilities as computational operations).

    2) You discuss the difficulty of answering intelligent design advocates. Complexity theory is relevant in a less trivial way than you think, and you will do fine if you adopt the following intellectually honest 3-tier approach:
    (i) it is theoretically possible that ID could be strongly supported by evidence we don’t happen to have uncovered yet (for example if our “junk DNA” turns out to cryptographically encode “Made by Yahweh” in a robust way) and ID supporters are free to go look for it
    (ii) There is serious technical work on the origin of the genetic code, by Dembski and others, which probably needs to be answered by a complexity theorist rather than any other kind of scientist
    (iii) The “irreducible complexity” argument that is most favored by IDers has a fatal flaw which opponents like Dawkins have not articulated properly: ANY system that evolves to perform complex functions, however redundant and Rube Goldbergish it is initially, will then tend to be streamlined by evolution, which will knock out inessential parts until an irreducibly complex system remains, at which point any further streamlining will fail to reproduce. Irreducible complexity should be EXPECTED, you just can’t get there by only building up, you have to get there by cutting down AFTER evolving a REDUCIBLY complex system.

    (3) I was one of the people you refer to whose intuition was that P=BPP already in the 1980’s; I remember explaining to Charles Bennett in 1985 or so why the existence of good pseudo-random number generators was likely to entail P=BPP (the alternative that BPP properly contained P would entail counterintuitive conspiracies that would prevent all possible PRNGs from being “irrelevant” to the problem in BPP/P ).

  62. Sniffnoy Says:

    I ask: Does this machine qualify for having consciousness?

    No, but your argument still fails as an argument for meat chauvinism. But really, even if we agreed the answer was no, that would not be evidence for meat-chauvinism. Consider: You’ve given an abstract description of a machine, and based your judgment of whether it is intelligent or not on that description! The machine could be implemented in metal or in meat; it doesn’t seem to make a difference to your argument. The fact of the matter is, that if you’re basing your judgment of consciousness on behavior rather than on substrate, you’re not supporting meat-chauvinism.

    Except, OK, I lied slightly in the above. You didn’t actually give a description of the machine’s behavior and base your judgment on that. What you actually described was the machine’s design process, and I suppose you could have judged partly based on that as well. So you may in fact judging on something other than just abstract behavior.

    And yet, design process is still not substrate. It still remains true that the design process above could be implemented for a metal machine or a meat machine, so the argument does not support meat-chauvinism.

    (By the way, I should point out — the whole “zeta function” part of your argument serves no purpose. Instead of “run through various domains of the zeta function”, you could have just said “run through all finite 0-1 strings in lexicographic order”.)

    So maybe you’re not arguing in favor of meat-chauvinism, but just against the Turing Test? The problem is, it doesn’t work very well as an argument against that either. You’re just saying, “Yes, you could beat the Turing Test by being intelligent, but you could also beat it by coincidence!” Which is certainly true, in much the same way that 2+2 could actually be 5 and nobody’s noticed because we all have the same bug in our brains. I.e.: Of course it can happen, but it’s extraordinarily unlikely. Any behavioral test you write can be beat; the question is how easy is it to beat — how much of an assurance does it give us about the things that beat it.

    And yes, “Any behavioral test you write can be beat” could be construed as an argument in favor of meat-chauvinism, but only if you’ve entirely missed the point. Any being-made-out-of-meat test can also be beat (though that’s more difficult). The point is that all knowledge is probabilistic, and the question is how much of an assurance does the test give us.

    Hell, although I know you’re conscious by any reasonable standard of “knowing”, I certainly don’t know with 100% probability — and all I have to go on is your behavior! You could *be* a domain of the Riemann zeta function for all I know! Except, of course, you couldn’t; that is to say, it’s technically possible, but so unlikely as to not be worth considering.

    Btw, I would recommend this post of Eliezer Yudkowsky, on playing “follow the improbability” with such thought experiments: http://lesswrong.com/lw/pa/gazp_vs_glut/

  63. Shtetl-Optimized » Blog Archive » Quantum Computing Since Democritus now out in the US! 20% discount for Shtetl-Optimized readers Says:

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

  64. Brian Rom Says:

    Scott, are you answering questions about specific math in the book? I am trying to work through the math of Ch. 9, Quantum with 2 years of college math in South Africa, (class of 1970 at University of Cape Town), so it’s a bit of a stretch, but, with some assists from you, I believe I can do it.

  65. Brian Rom Says:

    Guess not!

  66. Scott Says:

    Brian #64: If you have a specific question or two, go ahead and ask! But I can’t agree to an open-ended tutoring role.

  67. Brian Rom Says:

    Understood. And appreciate the offer. I’m having trouble with relationship between ket and vector notation. #1. On p114 you give the example of 3/5|3>+4/5|7> representing the previous vector. But how do you know how many zeroes were in the vector, and where they were located?
    #2: I don’t understand what you mean by ‘the state |0’ and What it means to ‘apply’ a matrix to a state.

    I suspect that what I probably need is a tutorial on kets and their arithmetic. I have tried in vain to find anything via online searches, so if you can point me somewhere, I’m certainly prepared to do the independent study.

    I find your top-down method of deriving some QM properties quite amazing, which is what is motivating me to try to follow the math. I’m also curious as to how this was received by your peers. Is it as original and impressive at it appears to me.

    Again, thanks in advance for any assistance you might be able to provide.

  68. Scott Says:

    Brian #67: Kets are just a notation for vectors, that’s it. When we write |1>,|2>,…,|n>, we mean the n basis vectors that span an n-dimensional space. You could also write



    Then a superposition

    |ψ> = a1|1> + … + an|n>

    just means the vector

    a1e1 + … + anen = (a1, …, an).

    From this perspective, the main function of the kets was to save you from using subscripts every time you wanted to name a vector ei.

    The one other thing to know is that, if |v> is a column vector, then <v| is the corresponding row vector. So for example, <v|w> means the inner product between the vectors v and w, and |v><v| means the outer product of v with itself (i.e., a rank-1 matrix).

    No, there’s almost nothing scientifically original in chapter 9 of QCSD—these are mostly well-known insights within quantum information and quantum foundations. At most, there’s something “pedagogically original” in choosing to explain quantum mechanics this way.

  69. Brian Rom Says:

    Scott, thanks. I think I got it now. As for being ‘pedagogically original’, the thought that, well, Democritus himself *could* have come up with the same results sounds a lot deeper than that. By the same token this line of reasoning could also apply to some of Dirac’s results, which we all agree are a lot more than just ‘useful’. I think there may be some deep epistemological implications. I mean, who’d have thunk that I, with my exceedingly limited knowledge of experimental and theoretical physics, could ever aspire to understanding the derivation of some of these foundational results. As a student all I can say is that this is immensely exciting. So I look forward to following you on this blog but cannot promise there will be no more simplistic appeals for help.



  70. Brian Rom Says:

    Scott, follow up.. Try as I can, I’m unable to understand the meaning of NP and P problems in any intuitive way. Their formal definitions are themselves dependent upon other, equally abstruse concepts: ‘nondeterministic Turing machines’, for example. I’d love to see you apply your legendary explantory skills to explicate these for the non-mathematician in way that we would also have some appreciation as to their significance. Thanks in advance.