211–220 of 373 posts
This may be an ill-formed question, but it's something I've been thinking about for a long time:
Do you think the human mind is equivalent to Turing machines, or somehow above it? Assuming we have an infinite tape/memory and time.
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You simply can't something 'physics' if its not testable. :)
That word 'testable', is very loaded. :) But I get what you mean. Are there things that we can't test that do exist?
Lots of people think so (e.g. unmeasurable things predicted by theory like parallel universes, but also things like evil or God or the color purple), but by definition it's hard to be very sure, or to transfer your own confidence in such things to others.
Lots of these kinds of questions reduce to quibbling about definitons; and also by definition, if we can't test the thing then the universe isn't going to punish us either way for believing or not.
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What does "linear" mean to you? Integration is linear[1]. The Hilbert space of all the functions you care about is linear[2]. Life is locally linear[3]. So maybe "non-linear" is just a red herring. 1. https://en.wikipedia.org/wiki/Linearity_of_integration 2. Not really but close enough. 3. I don't know what I mean either, but https://en.wikipedia.org/wiki/Linear_time-invariant_theory is interesting anyway.
I mean quantum computers that harness the NLSE in their computations somehow.
Hi Scott, Do you think there is a significant chance that quantum will never take off (i.e. there are non-obvious limitations that will prevent quantum architectures like superconducting qubits / trapped ions / quantum dots /... from ever outperforming classical supercomputers)? Related, what in your opinion is the best indicator (or would be the best indicator if demonstrated) of the potential of quantum devices?
The depressing possibility, of course, is that we never succeed in building useful QCs, but we also never learn anything deep about why we failed: it was just too complicated, too messy, and then at some point the funding ran out.
But I like to proceed on the assumption that the world is ultimately comprehensible (what other choice does one have in science? :-) ). On that assumption, if QC can never work, then there must be a deep reason that's not articulated in any of the existing physics books: either a breakdown of quantum mechanics itself, or else some new principle on top of QM that "screens off" or "censors" QC. Needless to say, the discovery of that principle would itself be a revolution in science -- indeed, I'd personally be more excited about it than a "mere success" in building scalable QC! (But my own bet is on the "boring, conservative" possibility, that QC can ultimately work.)
If we see the milestone of "quantum supremacy" achieved in the next few years -- i.e., a 50-70 qubit quantum computer used to solve some artificial sampling task many orders of magnitude faster than we know how to solve it classically -- that will obviously be one strong indicator that the potential of QC can be realized. An even better indicator would be the use of a quantum error-correcting code, like the Kitaev surface code, to keep encoded qubits alive for longer than the underlying physical qubits are staying alive for (or better still, to perform 1- and 2-qubit gates on them).
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That word 'testable', is very loaded. :) But I get what you mean. Are there things that we can't test that do exist?
Scientifically speaking, no. A scientific hypothesis must be falsifiable, and to be falsifiable it must be testable. I guess in some sense you could claim that there are hypothesis that are testable, but which we do not have the capacity to test. But then, is the claim that "one day in the future, we will be able to test this other claim" itself falsifiable? I'd argue not (it's a recognizable, not decidable claim, in…
This is certainly one understanding about what science should be (although not a scientific one interestingly enough). Personally I prefer Thomas Kuhn's demarcation, which by my understanding concentrates more on whether a scientific program is producing interesting predictions which turn out to be true.
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A quantum computer is a device that exploits constructive and destructive interference among exponentially many amplitudes , which are numbers that are closely related to probabilities but can be positive, negative, or even complex. If you feel that sentence wasn't clear enough, and it would take at least a few more paragraphs to flesh it out ... well, duh, what did you expect? :-D For a SLIGHTLY longer account, see…
Here's my attempt at a two sentence over-over-over simplification that at least gets people away from the "magic bit-sting that contains your answer." (It also harkens back to an old Einstein quote, so may be attractive to science writers.) Quantum computing is a technique that lets you sample a problem's answer-space using "loaded dice," such that the problem's correct answers correspond with probability spikes in y…
Hi Scott, Do you think there is a significant chance that quantum will never take off (i.e. there are non-obvious limitations that will prevent quantum architectures like superconducting qubits / trapped ions / quantum dots /... from ever outperforming classical supercomputers)? Related, what in your opinion is the best indicator (or would be the best indicator if demonstrated) of the potential of quantum devices?
Yes, I do think there's a significant chance of that. If it happens, my main interest would be to understand WHY. What are the non-obvious limitations that you mention? What is true about the world that makes it seem to have this exponential explosion of amplitudes, yet makes it impossible or infeasible to harness them for computation? The depressing possibility, of course, is that we never succeed in building useful…
By "significant chance" do you mean something like 10% or something like 70%?
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Scientifically speaking, no. A scientific hypothesis must be falsifiable, and to be falsifiable it must be testable. I guess in some sense you could claim that there are hypothesis that are testable, but which we do not have the capacity to test. But then, is the claim that "one day in the future, we will be able to test this other claim" itself falsifiable? I'd argue not (it's a recognizable, not decidable claim, in…
> A scientific hypothesis must be falsifiable This is certainly one understanding about what science should be (although not a scientific one interestingly enough). Personally I prefer Thomas Kuhn's demarcation, which by my understanding concentrates more on whether a scientific program is producing interesting predictions which turn out to be true.
In other words, the method to create interesting predictions which turn out to be true is to create interesting predictions, then test those predictions, and update your understanding of the world based on them. Once your world-model is good enough, your predictions will often be true. And, perhaps, eventually your predictions will be so often true that they become uninteresting, so you must move on to other questions.
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> A scientific hypothesis must be falsifiable This is certainly one understanding about what science should be (although not a scientific one interestingly enough). Personally I prefer Thomas Kuhn's demarcation, which by my understanding concentrates more on whether a scientific program is producing interesting predictions which turn out to be true.
I'm not speaking about science as a whole or a scientific program, but a scientific claim . CERN is certainly not falsifiable, but it produces predictions which (often) turn out to be true. It does so by devising falsifiable claims and then testing those claims. In other words, the method to create interesting predictions which turn out to be true is to create interesting predictions, then test those predictions, and…
The heliocentric model of the solar system made less accurate predictions than the geocentric model for years, because the geocentric model was mature and had had lots of tweaks applied to it. In that time, you could have asked the heliocentric model to make a prediction, and shown that it was wrong compared to the geocentric model. You would have been wrong to conclude that heliocentrism was wrong though, it just hadn't matured as a theory enough yet.
All models are wrong, but some are useful.
There are non-quantum physical systems that exhibits positive and negative amplitudes and interference.
Can I factor large numbers by throwing rocks in a lake and measuring the water height at the right place? Why not?