In a recent press conference Justin Trudeau answered a journalist who asked him (initially jokingly) to explain quantum computers. He obliged with a <1 minute explanation which seems to receive acclaim across the social media.

Here's a video I found in YouTube: Canadian Prime Minister Justin Trudeau Explains Quantum Computing and here's a transcript (from this website):

.. normal computers work, either there’s power going through a wire, or not. It’s 1, or a 0, they’re binary systems. Uh, what quantum states allow for is much more complex information to be encoded into a single bit. Regular computer bit is either a 1 or a 0, on or off. A quantum state can be much more complex than that, because as we know [speeding up dramatically] things can be both particle and wave at the same times and the uncertainty around quantum states [laughter] allows us to encode more information into a much smaller computer. So, that’s what exciting about quantum computing ..

Is this explanation accurate? I realize it's a short one and probably simplifies a lot of things, but is the main assertion, like (1) wave-particle duality and "uncertainty around quantum states" is what enables more packed encoding? Or (2) encoding more information into a smaller computer is what quantum computing aims at?

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    Will you be satisfied with the answer being declared "pop-sci right" or do you really want this subjected to professional levels of scrutiny? (Keep in mind that very few popular treatments come anywhere near conveying the subject at a level suitable for direction comparison to the real deal.) Apr 17 '16 at 20:58
  • What's the difference between "pop-sci right" and professional level of scrutiny?
    – user69715
    Apr 17 '16 at 21:32
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    There is at least one inaccurate assertion that you didn't challenge: the description of classical computing. The zero state does not correspond to "no power going through a wire", it corresponds to "some amount power going through the wire which has been established by convention to represent a 0 [typically less than the different amount of power which has been established to represent a 1]". In fact, I think it was GEB where it was pointed out that no power going through the wire is a great, physical, example of the state "Mu" (no answer is possible).
    – Dan Bron
    Apr 17 '16 at 21:39
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    In books written for a popular audience the author uses analogies and fuzzy word pictures to give the impression that you understand what is going on. Vast amounts of detail are elided and the analogies generally breaks down under various changes in the underlying set up so you can't use them for the basis of reasoning about situations very different from the ones the author presented. If the author is good that description is pop-sci right. But it isn't technically right and isn't a replacement for a textbook (not even a little bit). Apr 17 '16 at 21:40
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    quantum computing is a very complicated subject. Accuracy, brevity, clarity: Pick any two.
    – Shadur
    Apr 18 '16 at 8:31

This question is ultimately a matter of opinion - here are the opinions of a number of relevant experts:

Scott Aaronson, Associate Professor of Electrical Engineering and Computer Science at MIT,

On the one hand, the widespread praise for this reply surely says more about how low the usual standards for politicians are, and about Trudeau’s fine comic delivery, than about anything intrinsic to what he said. [...] On the other hand, I’d grade Trudeau’s explanation as substantially more accurate than what you’d get from a typical popular article. [...]

The humorous speeding up as he mentions particle/wave duality and the uncertainty principle clearly suggests that he knows it’s more subtle than just “0 and 1 at the same time,” and he also knows that he doesn’t really get it and that the journalists in the audience don’t either. When I’m grading exams, I always give generous partial credit for honest admissions of ignorance. B+.

A Motherboard article quotes a number of experts, and gives a final rating:

  • Romain Alléaume, Associate Professor at Telecom ParisTech and Paris Center for Quantum Computing:

    The beginning of Justin Trudeau’s explanation, about the difference between a classical bit and a quantum bit is absolutely correct. To be frank, the argumentation of Justin gets gradually more ‘uncertain’ when he says that the uncertainty principle implies that we can encode more information into ‘smaller computers’. [...]

    SCORE: 7/10

  • Amr Helmy—Director, University of Toronto’s Center of Quantum Information and Quantum Control

    SCORE: Too complex an issue to rank

  • Michele Mosca—University Research Chair and Co-founder, Institute for Quantum Computing, University of Waterloo. Founding Member, Perimeter Institute for Theoretical Physics

    The task is to explain quantum computing to a lay audience in a 100 words or so. It’s extremely hard, for even the best scientists and communicators, to get something like this both correct and interesting, especially in 100 words. He doesn’t say anything wrong. [...]

    SCORE: 9/10

  • Aephraim Steinberg—Professor of Physics at the University of Toronto and member of Center of Quantum Information and Quantum Control

    To put it bluntly, if you think about the level at which any scientist given a few minutes to try to explain quantum computing to him would have tried to pitch it, he probably got the gist and explained it back as well as you could imagine anyone doing. [...]

    SCORE: 7/10

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    @user69715 The fact that single qubit is in an uncertain ("more complex") state doesn't directly imply that it contains more information than an ordinary bit. It actually doesn't. It's still just a number. The "more information" comes from the ability to create multi-particle (multi-qubit) states, where all of them interact in a non-classical manner. One-by-one qubits are not more useful than classical ones.
    – sashkello
    Apr 17 '16 at 23:54
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    <...> Now, even then, it's not immediately clear why this is better than classical computer, because, again, even if they are combined in complex states and measured together, each measurement considered separately is, yet again, just one number. But the thing is, I don't think there is any easy way to explain it but write down quantum algorithms and equations. It's really non-obvious, how it's able to outperform the classical computer. The explanation he gave is more or less what professors tell the public when they have less than a minute and don't want to bother with lengthy explanations.
    – sashkello
    Apr 18 '16 at 0:35
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    <...> The better way to put it, though, would probably be to tell that the "more information" encoded in quantum states allows for some tasks to be performed more efficiently. The point is not that you can store more information in less space, but that you can solve exponentially hard problems in polynomial time, by using complex interacting entangled quantum states. So, roughly, instead of 2^n operations your task requires n^2 operations, or something along those lines. The former quickly gets too big for the power of all the world's computers to solve, while the latter is still manageable.
    – sashkello
    Apr 18 '16 at 0:44
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    Those comments don't constitute a Skeptics answer until @sashkello runs down a few review articles to back them up (not withstanding that he's a least a narrow gauge expert). The "no original research" rule strikes again. Apr 18 '16 at 3:57
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    @user69715 I agree with dmckee. This shouldn't be an answer. I was merely providing some background concerning what those quotes in the existing answer likely mean. "the explanation good enough (for a politician) but not 100% technically accurate." - this is the best summary, really, everything else delves into the topic of quantum theory rather than skepticism. And as I mentioned above, you can't make a technically right explanation to an audience, which hasn't attended an introductory course in quantum physics, so any 1-minute explanation will be "technically wrong" on some level.
    – sashkello
    Apr 18 '16 at 4:12

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