Quantum Advantage

I’ve had quite a few conversations lately about a comment I left on Scirate. The paper at that link, “Quantum advantage with shallow circuits” by Sergey Bravyi, David Gosset, Robert Koenig, shows a provable separation between analogous classes of quantum and classical circuits, even when the quantum circuit is restricted to nearest-neighbor gates on a 2D grid. This is a fantastic result! My comment, however, wasn’t regarding the result, but rather the title of the paper. I’m just happy that they called it a “quantum advantage” instead of using that other term…

The term “quantum supremacy” is the fashionable name for the quantum experiments attempting to beat classical computers at some given task, not necessarily a useful one. According to current usage, the term (strangely) only applies to computational problems. The theoretical and experimental work towards demonstrating this is wonderful. But the term itself, as any native English speaker can tell you, has the unfortunate feature that it immediately calls to mind “white supremacy”. Indeed, one can even quantify this using a Google ngram search for *_ADJ supremacy over all books in Google’s corpus between 1900 and 2008:

None of these terms has a particularly good connotation, but white supremacy (the worst on the list) is an order of magnitude more common than the others and has, on net, been growing since the 30s. For almost every native speaker that I’ve talked to, and quite a few non-native speakers as well, the taint of this is hard to escape. (For speakers of German or French, this word is a bit like “Vormachtstellung” or “collaboration” respectively.)

The humor surrounding this term has always been in bad taste — talking about “quantum supremacists” and jokes about disavowing their support — but it was perhaps tolerable before the US election in November. Given that there are several viable alternatives, for example “quantum advantage” or even “quantum superiority”, can we please agree as a community to abandon this awful term?

This isn’t about being PC. And I’m not trying to shame any of the people that have used this term. It’s just a poor word choice, and we don’t have to be stuck with it. Connotations of words matter: you don’t say someone is “scrawny” if you mean they are thin, even though my thesaurus lists these words as synonyms. Given the readily available alternatives, the only case I can think of for “supremacy” at this point is inertia, which is a rather poor argument.

So please, say it with me now: quantum advantage.

Update: Ashley Montanaro points out that “advantage” should potentially be reserved for a slight advantage. I maintain that “superiority” is still a good choice, and I also offer “dominance” as another alternative. Martin Schwarz suggests some variation of “breaking the X barrier”, which has a nice feel to it. 

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13 Responses to Quantum Advantage

  1. Ashley Montanaro says:

    Hi Steve,

    I think it’s a good idea to have this debate, and as with many other people I agree that the word “supremacy” is far from ideal and leaves a bad taste in the mouth, for the reasons you give. However, unfortunately I don’t think that “advantage” or even “superiority” mean the same thing, so I don’t think they’re good replacements.

    My feeling is that one can demonstrate quantum advantage without demonstrating quantum supremacy. Even Deutsch’s algorithm is an example of quantum advantage, but quantum supremacy is doing something which you could never do in a reasonable time on a classical computer. For example, something that would need 100 years of supercomputer time. Also, I think that “quantum supremacy” specifies an event: the first time that quantum computers dramatically outperform classical ones. I’m not sure that “quantum advantage” can be interpreted as an event.

    The use in the paper you mention of “advantage” is completely right, in my opinion, because they show that you can do something with constant-depth quantum circuits that you can’t do with constant-depth classical circuits. But this isn’t an example of quantum supremacy, because you can also do it with a polynomial-time classical algorithm.

    If there were an alternative word that would be an immediate drop-in replacement with the same meaning, but not the same unpleasant connotations, that would be great. But I’m not sure there is, although any suggestions would be welcome! I think it would need to be a noun, and one that can specify an event. Of course, we could all agree not to use any term at all, but this seems a shame, as having something specific to use does seem useful.

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    • sflammia says:

      These are good points, Ashley. I think “superiority” does achieve the goals that you want for the term. Even though there are some phrases that have negative connotations with superiority, it also has more neutral meanings as well, like in the phrase “moral superiority”. “Dominance” is perhaps another choice; what do you think of that one?

      Or maybe we could go with “classical inferiority”. 🙂

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      • Ashley Montanaro says:

        I’m not sure… I think the classical folk see us as acting overly superior as it is 🙂 And to me it seems like “superior” might mean “only a little bit better”.

        “Dominance” is interesting because in mathematical usage it seems to make sense (eg. one term dominating an expression) – though the dictionary suggests it may have similar problems with connotations (Merriam-Webster’s first definition is “controlling, prevailing, or powerful position especially in a social hierarchy”…).

        In many ways I like Raphael’s suggestion of quantum victory, but perhaps this too seems too antagonistic. Quantum triumph? But then there’s no notion of comparison…

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  2. Raphael says:

    Quantum victory? (Meant in jest.)

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  3. aram says:

    So should we also stop saying “naval supremacy” and “commercial supremacy” and so on?

    If Nazis talk about “racial hygiene” laws, should we stop using the term “hygiene” in other contexts?

    I get how the word “supremacy” reminds you of something unpleasant but I don’t think anyone would interpret it as an endorsement of white supremacy.

    A different objection you could raise is to the term “quantum.” These experiments really demonstrate “computational supremacy” analogous to earlier quests for things like maritime supremacy.

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    • sflammia says:

      I think your last point is very insightful, and it helps to highlight why the first point you make is a weak argument. You first ask the rhetorical question of whether we should stop using terms that have been tainted by unpleasant associations. Well, I’m not saying that “yes” or “no” follows logically; however, we have a choice. Given the readily available alternatives like “superiority” or “dominance”, why would you actively choose a word that did have negative associations? Regarding the terms “naval supremacy”, etc., I have also heard “superiority” used in that context (much more often in my experience). And regarding the feeling of righteousness (“I won’t let them take my word, so I’ll keep using it in protest!”), it’s not like we’re a marginalized group that is reclaiming a term. So we shouldn’t adopt the term as a form of protest or resistance.

      In addition, your analogy is weak because word pairs like “oral hygiene” are well established and have no negative connotations. “Supremacy” is definitely distinct in that regard since it is strongly associated with just one additional qualifier. And I’m certainly not saying that using it is an endorsement of white supremacy, or could even reasonably be interpreted as such. Again, the point is that we have a choice. Why continue doing something unpleasant if you don’t have to?

      Your last point, that it is really “computational supremacy”, greatly clarifies why “quantum supremacy” is a bad term. The word “quantum” is often used in our community as the name of our tribe! To say “X supremacy” where X is the name of a group of people is definitely crossing a line in my mind. The fact that people mention “quantum supremacists” and so on really reinforces this reading. Whereas if X is a resource, the connotations are a lot milder. Saying “quantum computational supremacy” or even just “computational supremacy” is orders of magnitude better to my ears since it completely removes the tribal associations.

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  4. Since the scientific aim of “quantum supremacy” experiments is to provide experimental evidence against the Extended Church-Turing thesis (see e.g. arXiv:1011.3245), why don’t we use “breaking the Church-Turing barrier” instead of “achieving quantum supremacy”. “Breaking a barrier” is shorter and sounds slightly more catchy than disproving (or providing evidence against) an (extended) thesis, yet it’s quite to the point and not an exaggeration. It has desirable positive connotations of speed (as in sound, or speed-of-light), practical hardness, and entering a new regime where new rules apply, and no negative ones, as far as I can tell.

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    • mick says:

      I quite like this suggestion Martin! However, it’s a little awkward to use in practice, e.g. “breaking the quantum barrier(edness ? :-)) is achieved with fidelity x and number of qubits y” is a little tricky. I do think it’s in the right direction.

      In talks lately I’ve been trying to use “beyond classical”, “unambiguous quantum advantage”, and “supra-classical”. All of them have drawbacks. I like the word “beyond” a lot as it has connotations of exploration. On that, “beyond the quantum frontier” is a nice turn of phrase – also more-or-less due to John Preskill.

      I should say I agree with pretty much all of what Ashley is saying above. Though, we have (obviously) discussed this a lot.

      In practice that “quantum supremacy” has fallen into common usage in the science media without too much complaint.

      Finally I should say that bconnotations remain bad until they are challenged. I believe that conceding, or reserving, words for extremists (esp. when they have other uses) might not be a great idea for improving political discourse. On the other hand I’d like a more positive term, like “beyond”, as it captures the imagination a bit better.

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      • Ashley Montanaro says:

        I like “breaking the X barrier” for some X, but I’m not sure that X=Church-Turing works – after all, it’s only the extended Church-Turing thesis that’s falsified by the quantum experiment, and neither Church nor Turing actually proposed that.

        Maybe we’ll just end up with a variety of phrases for different contexts (e.g. “supra-classical” as an adjective, “supremacy” as an event, and “beyond the classical frontier” as a longer phrase). It’s interesting that John Preskill didn’t use the word “supremacy” in the title of his original article, but went for something longer and more positive.

        I also agree with Mick that it’s a shame to just give up on a perfectly good word because of its usage by a group of extremists.

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  5. Kristin says:

    What about a quantum ‘tipping point’?

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  6. Anthony Laing says:

    Variations on supremacy feel less harsh: supreme court, supremeness (is that in Bill & Ted?), chicken supreme, Diana Ross and the Supremes… Thinking about it, I’d pay good money to see a Mel Brooks production of Baby Love by Diana Ross and the Supremacists.

    Anyway, my suggestion is for Quantum Transcendence.

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    • sflammia says:

      Yeah, these other variations have no negative connotations. I think Aram’s comment has really clarified for me that the reason “quantum supremacy” sounds so bad is that we really do use “quantum” as the name of our community, and “(group of people) supremacy” is just a bridge too far.

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  7. John Sidles says:

    At QIP 2017 (in Seattle) the phrase “quantum ascendancy” was heard.

    This phrase (as it seems to me) aptly describes the study of quantum dynamics in respect to worthy pursuits like “computational ascendancy”, “observational ascendancy”, and “metrological ascendancy” (and more).

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