111–120 of 215 posts
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Isn't it just Enormous : enormity :: huge : hugeness?
Not quite. Enormous : enormousness :: huge : hugeness. Enormity = Immense scale of evil (e.g., the "enormity of the holocaust")
"Enormousness" isn't a word in common usage that I'm aware of.
Earlier quoted context omitted.
Holy hell. > > In a superconducting circuit, conduction electrons condense into a macroscopic quantum state, such that currents and voltages behave quantum mechanically [2, 30]. Our processor uses transmon qubits [6], which can be thought of as nonlinear superconducting resonators at 5 to 7 GHz. The qubit is encoded as the two lowest quantum eigenstates of the resonant circuit. Each transmon has two controls: a micro…
So I'm not super familiar with quantum computation, but I did do my undergrad research in QM (specifically, how chaotic behavior depends on the scale of nonlinear quantum systems) and I can take some informed guesses about what these words mean. It's actually super cool! In a superconducting circuit A circuit is a loop of something. Probably a solid material, like a metal or carbon, though it could be something more…
> A qubit can be |1>, but it could also be (1/sqrt(2) |0>) + (1/sqrt(2) |1>). We call that a "cat" state, incidentally, because it's "half 1, half 0"--like Schroedinger's Cat, half alive and half dead. Again, the coefficients here are, in general, complex numbers, but we're gonna gloss over that.
In case anyone is interested in not glossing over this part, this [0] lecture by Scott Aaronson is an excellent introduction to the crazy world of complex probability amplitudes. It doesn't assume much more than some basic linear algebra, and does a good job of developing at least a little bit of an intuition for some of the concepts in Aphyr's comment.
> It’s like, if you believed that useful air travel was fundamentally impossible Uh, there are birds. Literally everyone thought useful air travel was possible, and not only possible, but so easy that a Darwinian process was able to produce it, not once, but literally thousands of times, in thousands of ways. ---- But looking at the actual "experiment", I don't count that as computation in any meaningful sense, and m…
Imagine a bunch of magnets. Imagine forcing them into a "frustrated" configuration; maybe you have them all on a grid, and you have servomotors that can rotate them to face any way you like. The servomotors are strong, so counteracting the magnetic forces is easy for them. You design an appropriately frustrated configuration, and then release all of the magnets at once. What configuration do they rotate into?
A quantum annealer is conceptually similar. Each qubit, on a regular, patterned graph, has connections to its neighbours. You can leave these alone (no corellation) or tune them up to +/- 1, corresponding to "must be the same as this other qubit" and "must be different than this other qubit". You can also bias each individual qubit to be a 0 or a 1.
Then, you let it go, and it anneals, and you observe the result. Your goal is to get to the _lowest energy state_ possible: the least possible frustration remaining.
In our magnet example, it would be as few magnets as possible wanting to move - if you poked them with your finger they'd want to go back into their current state. You could imagine that your magnets might not get down to their absolute lowest energy state; maybe it would take too much energy to flip from their starting state to that lower state. In a quantum system, because of tunneling, the system can reach these lower ground states. Rather than being in a fixed position the way our magnets were, qubits are in a quantum superposition, so they can reach a lower energy state without having to climb up that energy hill. Or so we're lead to believe by the numbers, anyway; I'm not a physicist.
Now, if you can map some useful computational question onto the original configuration of qubits that is answered by the ending position, you've got yourself a useful quantum computer. This is the hard part! The key is to use optimization algorithms where a lower energy state = a more optimized result. If you can do this, there's a ton of employment waiting for you.
Then, if you want "quantum supremacy", it's matter of providing more optimized answers in less time, particularly as the problem scales up in complexity. There does indeed appear to be a crossover point coming in a decade or so, at least for the small class of real-world problems that the Ising Hamiltonian works for.
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Well D-wave is evaluated on an optimization task. This Google thing isn’t even trying to solve a real problem. What says you can’t get some very hard to replicate random bits out of a D-wave?
If D-Wave could achieve quantum supremacy, they definitely would, and would heavily publicize it. They haven't, which gives us strong evidence that they can't right now.
> It’s like, if you believed that useful air travel was fundamentally impossible Uh, there are birds. Literally everyone thought useful air travel was possible, and not only possible, but so easy that a Darwinian process was able to produce it, not once, but literally thousands of times, in thousands of ways. ---- But looking at the actual "experiment", I don't count that as computation in any meaningful sense, and m…
Perhaps it will make more sense to explain how a D-Wave machine works, as (a) they actually exist and you can use one today for free online, and (b) it's way simpler than a gate model QC is. Imagine a bunch of magnets. Imagine forcing them into a "frustrated" configuration; maybe you have them all on a grid, and you have servomotors that can rotate them to face any way you like. The servomotors are strong, so counter…
Yes, I agree. But this has not been demonstrated. What's being demonstrated (apparently) is that measuring a quote-unquote "quantum computer" doing whatever it does naturally is easier than simulating said quantum computer classically. Well, yeah. Duh.
That's the same thing as "rendering" a scene with an unbiased renderer vs. setting up that same scene in reality and using a camera. No one in their right mind would point to the camera and say they'd create a next-gen, heretofor impossibly fast unbiased rendering algorithm.
Technically, the digital camera is "computing" the same result—but no one would call it that, and IMO, the same is true of what is being discussed in the FAQ. It's literally NOT COMPUTATION, which brings us back to your line:
> Now, if you can map some useful computational question onto the original configuration of qubits that is answered by the ending position, you've got yourself a useful quantum computer. This is the hard part!
It's not only the hard part, it's the only part that matters. Until then, you have AT BEST a "quantum camera". Potentially useful, perhaps—but it's not a computer, or computation.
Anyway, thanks for responding. Much better than drive-by downvoters probably hoping to get PhDs in this stuff.
Also, my intent is not to belittle Google's engineering effort. In the same way that I wouldn't belittle Sony for making 24mmx36mm backlit CMOS sensors. It's impressive! Good for them. But it's not computation, and it definitely doesn't establish some kind of "quantum computing supremacy" (since no meaningful computation is being done). When they stop handwaving about mapping actual computation problems to the scene they've set up and are measuring, then I'll get excited. Maybe it's doable, maybe not. But a quantum camera, AT BEST, is one step along the path...
>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.
> It’s like, if you believed that useful air travel was fundamentally impossible Uh, there are birds. Literally everyone thought useful air travel was possible, and not only possible, but so easy that a Darwinian process was able to produce it, not once, but literally thousands of times, in thousands of ways. ---- But looking at the actual "experiment", I don't count that as computation in any meaningful sense, and m…
If it goes well, the history of quantum computing will be divided up in to three eras: the era of twisty philosophical arguments that it's working ("the molecule is simulating itself"), the era of academic arguments that it's working ("we can solve this one carefully constructed problem") and the era of practical arguments ("Amazon is selling QC time for $20/kilogate-bit, what do you mean it's not possible?"). Quantu…
What are the theoretical models for the energy cost of computing on a qubit? I'll be excited for QC when there is known way (even with some handwaving and future-tech plans) to compute a non-trivial result for a reasonable sum, such as "crack someone's private RSA key for under $10M of compute cost"
Earlier quoted context omitted.
Not quite. Enormous : enormousness :: huge : hugeness. Enormity = Immense scale of evil (e.g., the "enormity of the holocaust")
As a native English speaker, I can't say I've found this to be the case. "Enormity" does tend to be used for dramatic effect, most often on moral issues, but I don't think that makes Scott wrong to use it here. I don't know if I've seen "enormousness" before this thread.
When I visited Iceland, I remember a sign in English that said a cliff was insafe [sic]. `in` being a Latin morpheme, and safe being Germanic.
> It’s like, if you believed that useful air travel was fundamentally impossible Uh, there are birds. Literally everyone thought useful air travel was possible, and not only possible, but so easy that a Darwinian process was able to produce it, not once, but literally thousands of times, in thousands of ways. ---- But looking at the actual "experiment", I don't count that as computation in any meaningful sense, and m…
I have no comment on the QC claims, but regarding the flight analogy, it seems you're being disingenuous: https://www.xaprb.com/blog/flight-is-impossible/