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I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

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Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#251

How do you feel about the Axiom of Choice?

It feels really uncomfortable that, if you have infinitely many people wearing red or blue hats that they can't see, then they can all guess their own hat color with only finitely many of them being wrong. Not to mention Banach-Tarski and a hundred other strange phenomena. This all militates toward rejecting AC. But then, if we reject AC, we can have infinite sets that are incomparable (i.e., they're not isomorphic a…

Does it make more sense to use an analogy where we have infinitely many people with a strongest 'thought' (a statement they hold as most true), they can all guess their own thought with only finitely many of them being wrong?

My apologies if that sounds ridiculous, I'm honestly not that attentuated to making much sense to myself.

> Thinking about such things for too long makes me feel grateful that I spend most of my time in the finite world

Hmm.

Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#252
Hi Scott,

Of the two main possible applications of QC, i.e. computational chemistry and cryptography, it's often just cryptography that is mentioned in the media. The Wikipedia entry on QC, in its "Potential" section, discusses mostly cryptography, while only two sentences are dedicated to chemistry. Cryptography is also used as the toy-problem for QC prototypes, i.e. factoring integers.

However, as I understand it, QC-for-cryptography will break existing techniques, and will not (from an application standpoint) bring anything new to the table.

Therefore, my question: does QC have a PR-problem?

Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#253

Can you describe how different the operating system would be from the traditional operating system we use today for quantum computing? Broad question but any specifics you can answer....

More importantly, what would quantum web browsing look like.

Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#254
post #3

Hi Scott, Shtetl-Optimized's tagline is famously "Quantum computers would not solve hard search problems instantaneously by simply trying all the possible solutions at once". What phrase do you think should replace 'trying all the possible solutions at once' in the public conciousness as a succinct description of the mechanisms of a quantum computer? Or is this topic simply too complex to be distilled into a neat syn…

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…

“Quantum Computing is the exploitation of quantum state evolution to perform computation.”

Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#255
post #246

Earlier quoted context omitted.

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…

Ok, I'll try another attempt at explaining the stuff :P Not sure if correct, because I'm not a parent :P neither a quantum scientist actually, just dabbled a tiny bit in QC at one point :) So you can choose whether to believe my words or not :) Imagine you are a parent/teacher in a room full of happy kids, playing their kid games. Some kindergarten playground or something. They're generally all doing some kind of stu…

As someone still trying to understand the essence of quantum computing, your analogy to me can be summed up as coherence only comes from coherence. Which to me is too general, and describes computing as a whole. How coherence is determined in the particular case of quantum computing as opposed to classical computing is the meat and potatoes that I'm looking for.

Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#256

Hiya, Scott! I recently heard the first episode of Rationally Speaking podcast episode where you were the guest (yes, I'm catching up with the RS Archives during my long commute). I've also started reading QCSD (hey, if it's going to be our decade's GEB, we may as well give it an acronym. :: grin:: ) I've already corrected my very mistaken understanding of how QC works, as in the tagline of your blog. Are there any o…

Sure, you could shake off the idea (if you haven't already...) that quantum entanglement means communication faster than light. This is, interestingly, exactly the same kind of error as the one that says that a quantum computer is just like a classical computer but with exponential parallelism. Namely, you look at the resources that would be needed to simulate a quantum system using a classical system (faster-than-light communication in the one case, exponential parallelism in the other). You then confuse those with the resources that the quantum system itself provides you.

In reality, quantum mechanics is carving out a third profile of abilities, which is neither as weak as the classical profile, nor as strong as the thing that people mistakenly overcorrect to once you tell them that the classical profile is inadequate. E.g., you can violate the Bell inequality but NOT send instantaneous signals; you can solve factoring in polynomial time but probably NOT NP-complete problems. As I like to say (someone already quoted it elsewhere), it's a sufficiently strange state of affairs that no science-fiction writer would have had the imagination to invent it.

Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#257
post #246

Earlier quoted context omitted.

Ok, I'll try another attempt at explaining the stuff :P Not sure if correct, because I'm not a parent :P neither a quantum scientist actually, just dabbled a tiny bit in QC at one point :) So you can choose whether to believe my words or not :) Imagine you are a parent/teacher in a room full of happy kids, playing their kid games. Some kindergarten playground or something. They're generally all doing some kind of stu…

As someone still trying to understand the essence of quantum computing, your analogy to me can be summed up as coherence only comes from coherence. Which to me is too general, and describes computing as a whole. How coherence is determined in the particular case of quantum computing as opposed to classical computing is the meat and potatoes that I'm looking for.

Sorry, don't think I can do more at this point; I once managed to understand the Shor's algorithm from some book; but I didn't reinforce it, and now I'm left only with a vague recollection of the main a-ha moment... Though I actually don't really get what do you mean by coherence here (esp. in the area of classical computing).

Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#259
post #211

Hi Scott, 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.

There are really two questions here.

The first one is, can the human brain be simulated by a Turing machine in its input-output behavior (to a suitable precision, given appropriate initial data, yada yada)? Note that, even though you specified "infinite tape/memory and time," from the outset I'm going to outlaw "simulations" that simply cache what the human would do in response to every possible stimulus in a gargantuan lookup table. For that kind of simulation trivially exists, and its existence tells us nothing interesting. I'll insist instead that the simulation be "reasonable"---so, at a minimum, that it simulate the brain without an exponential blowup in size.

I don't know for certain, but as a believer in the physical Church-Turing Thesis, my guess is going to be yes, this is possible. I.e., I guess that the laws of physics are fully computable---that there's nothing in them like what Roger Penrose wants---and I see no evidence that the brain can violate the laws of physics that govern everything else in the universe.

(Even here, though, there remains the extremely interesting question of whether, even in principle, one could scan a specific person's brain well enough to "bring additional copies of the person into being," without simply killing the person if one tried. My friends in the futurist and singularity movements expect that the answer is yes, but if one needed to scan all the way down to the molecular level, then the No-Cloning Theorem of quantum mechanics would certainly present an obstacle. For my thoughts and speculations about this question, see my "Ghost in the Quantum Turing Machine" essay, which was referenced elsewhere on this thread: https://www.scottaaronson.com/papers/giqtm3.pdf )

Anyway, the second question is whether, even if we agree that a human brain can be simulated by an appropriate Turing machine, there's some special sauce of consciousness that makes there be something that it's like to be us, but nothing that it's like to be a conventional Turing machine. I.e. there's Chalmers' "hard problem of consciousness."

Here I'm going to plead ignorance, with my extenuating circumstance being that we're up against arguably the ultimate mystery of existence. :-)

Yes, I feel like there's something that it's like to be me. (Though if I were a philosophical zombie, just a glorified Turing machine made of meat, I could've told you exactly the same thing, so you should take whatever I have to say about this with a grain of salt. :-) )

And yes, I take it as axiomatic that there's similarly something that it's like to be you---or for that matter, to be a chimpanzee or a dog (but an ant? a bacterium? unclear). No, I don't understand it. No, I don't know what properties of a computational process are either necessary or sufficient to cause there to be something that it's like to inhabit that process; I don't know how we should build an AI either to ensure that it's conscious or to ensure that it isn't. In practice, we'd probably have to extend a presumption of consciousness to anything that behaved sufficiently similarly to us---that, famously, was Turing's point in 1950. But even here there are many uncertainties: for example, would you still take a machine to have "passed the Turing Test" if you could perfectly predict everything it would say given a copy of its source code---not just in principle but in practice?

Re: I'm Scott Aaronson, quantum computing/computational complexity researcher. AMA

#260
post #3

Hi Scott, Shtetl-Optimized's tagline is famously "Quantum computers would not solve hard search problems instantaneously by simply trying all the possible solutions at once". What phrase do you think should replace 'trying all the possible solutions at once' in the public conciousness as a succinct description of the mechanisms of a quantum computer? Or is this topic simply too complex to be distilled into a neat syn…

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…

A quantum computer is a high-tech ouija board.
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