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>Q12. Even so, there are countless examples of materials and chemical reactions that are hard to classically simulate, as well as special-purpose quantum simulators (like those of Lukin’s group at Harvard). Why don’t these already count as quantum computational supremacy? >Under some people’s definitions of “quantum computational supremacy,” they do! The key difference with Google’s effort is that they have a fully programmable device—one that you can program with an arbitrary sequence of nearest-neighbor 2-qubit gates, just by sending the appropriate signals from your classical computer. >In other words, it’s no longer open to the QC skeptics to sneer that, sure, there are quantum systems that are hard to simulate classically, but that’s just because nature is hard to simulate, and you don’t get to arbitrarily redefine whatever random chemical you find in the wild to be a “computer for simulating itself.” Under any sane definition, the superconducting devices that Google, IBM, and others are now building are indeed “computers.” This is the core of it to me. It's a question of 'some people’s definitions of "quantum computational supremacy."' Many people say that the definition here is a crappy one, and sure this shows a form of it, but not the kind to justify the hype. Sure, it's fully programmable, but not so programmable as to do anything that anyone cares about (even a teeny tiny few-bit version of something people care about) better than we can otherwise. To appeal back to his analogy to the wright brothers, it's like they carved a frisbee from a stick while working towards airplanes. It's amazing that they carved a log into a neat shape you can throw further than another log, and the hype train is saying that it's fully carve-able, so it counts as "airplane-supremacy," but that's a crappy definition and not what we're waiting for. |