Earlier quoted context omitted.
Sounds like Fusion. That’s still going on after 60 odd years.
If something sounds too good to be true, it probably is.
Sulfa. White swans do come along, they're just incredibly rare.
The Case Against Quantum Computing
11–20 of 89 posts
Re: The Case Against Quantum Computing
#12I still need to gain the intuition for why a quantum computer can operate on some kinds of things "faster". I've read some of the math, but that did little to satisfy me (I need to study it more clearly). But all of this seems in a tragic state at the moment. Allowing rampant misinformation and hype as to what these machines are actually capable of.
If you are specifically interested in building up the mathematical intuition, check out "Quantum Computing since Democritus" by Aaronson - it excels at presenting the intuition. For less comp-sci and more physics look at the standard references: Nielsen and Chuang's book and Preskill's lecture notes.
Re: The Case Against Quantum Computing
#13Earlier quoted context omitted.
Sounds like Fusion. That’s still going on after 60 odd years.
With one major difference. We know that fusion in some form is possible (for example, in the sun, or in a hydrogen-bomb). The difficulty is doing it at a reasonable scale. It's less clear that quantum computing is possible.
I mean we already have quantum computers too. https://quantumexperience.ng.bluemix.net/qx/experience The trouble here is also scaling, but in the upward direction.
Re: The Case Against Quantum Computing
#14Had to read to the bottom to get to the (really weak) "case against Quantum Computing": > I believe that, appearances to the contrary, the quantum computing fervor is nearing its end. That’s because a few decades is the maximum lifetime of any big bubble in technology or science. After a certain period, too many unfulfilled promises have been made, and anyone who has been following the topic starts to get annoyed by…
There's certainly a bubble here; trivially obvious, but there are also very good technical arguments in that article. FWIIW Dyakonov has been saying the same thing since the bubble got started in 2000 or so.
Re: The Case Against Quantum Computing
#15Had to read to the bottom to get to the (really weak) "case against Quantum Computing": > I believe that, appearances to the contrary, the quantum computing fervor is nearing its end. That’s because a few decades is the maximum lifetime of any big bubble in technology or science. After a certain period, too many unfulfilled promises have been made, and anyone who has been following the topic starts to get annoyed by…
The technical argument is absolutely clear: quantum computing cannot work because it relies on manipulating and measuring an absolutely astronomical number of continuous variables with near-infinite precision. The argument may or may not be correct, but it deserves something more thoughtful than a dismissive response that doesn't even recognise the basic point the author is making.
This is one of the standard complaints (the gist of it being that quantum computing is some form of analog computing, i.e. requiring near-infinite precision). For researchers in the field it becomes rather frustrating to have to repeat the same response without being heard, so I can understand the annoyance expressed in the parent comment. For what is worth, here is a good explanation of how this complaint misrepresents the whole premise of quantum computation (in particular, point 6): https://www.scottaaronson.com/democritus/lec14.html
Re: The Case Against Quantum Computing
#16I still need to gain the intuition for why a quantum computer can operate on some kinds of things "faster". I've read some of the math, but that did little to satisfy me (I need to study it more clearly). But all of this seems in a tragic state at the moment. Allowing rampant misinformation and hype as to what these machines are actually capable of.
If you are specifically interested in building up the mathematical intuition, check out "Quantum Computing since Democritus" by Aaronson - it excels at presenting the intuition. For less comp-sci and more physics look at the standard references: Nielsen and Chuang's book and Preskill's lecture notes.
Thanks for the links. I'll start here: http://www.theory.caltech.edu/%7Epreskill/ph219/index.html#l... and probably get the books too (hey, they're cheap on amazon... god I hate myself).
Re: The Case Against Quantum Computing
#17I still need to gain the intuition for why a quantum computer can operate on some kinds of things "faster". I've read some of the math, but that did little to satisfy me (I need to study it more clearly). But all of this seems in a tragic state at the moment. Allowing rampant misinformation and hype as to what these machines are actually capable of.
I'm going to butcher a lot of the physics here, but here's the gist of it that should avoid some quantum myths:
The quantum state of a system is not described by a simple real probability but by a complex number. This means that there is an additional degree of freedom that you can adjust in a quantum state that doesn't change its probability of occurring. The nature of entanglement means that there is constructive and destructive interference when you go through certain quantum operations.
Traditionally, a quantum word can be thought of as being a probability distribution over the various possible values of the word. You can build quantum gates that act like classical gates on the binary values, and it's this property that often causes people to describe a quantum computer as executing every possibility in parallel. The difficulty is that the result you get is sampled by the probability distribution, which means you need some sort of interference between the results to allow you to boost the probability of picking the answer you want. A quantum speedup is only possible when you can find the interference. In the case of Shor's algorithm (for factoring), the interference is basically a quantum variant on FFT; in the case of Grover's algorithm (finding x such that f(x) = y), the interference is something that redistributes the probabilities among a plane of the sphere.
Re: The Case Against Quantum Computing
#18The core argument here, concerning the number of variables that need to be manipulated, isn't very clear to me - I can't tell if that's because it's an unclear argument in general, or if the author tried to simplify it for laypeople to the extent that it became unconvincingly vague for people who know a thing or two about the subject area. Given the status of the author, I'm willing to give him the benefit of the doubt (and also assume that some clarity was lost in translation).
Here's an easier-to-follow argument I've heard before (also simplified for laypeople) that might be close enough to the one the author intends to make to be useful:
Quantum algorithms are supposed to be much more efficient than conventional algorithms at certain kinds of tasks. That efficiency is calculated with the assumption that each system starts in a state where it's prepared to execute the algorithm. For conventional computers, that makes sense for a number of reasons (e.g. data/program input is linear). For quantum computers, this assumption doesn't necessarily make sense because it takes a significant amount of work (in terms of measurements, etc.) to get the system (the machinery and physical representation of the initial data) into the right quantum state. In fact, the amount of work required scales horribly with the size of the input (in terms of qubits). If you think of those state preparation steps as part of the cost of the algorithm, the quantum algorithms won't, in general, outperform the classical ones.
I've been out of the quantum computation loop for nearly a decade, so I have no idea whether that's a fair way of presenting the problem, but hopefully it helps someone understand the claims being made in the article.
Re: The Case Against Quantum Computing
#19I still need to gain the intuition for why a quantum computer can operate on some kinds of things "faster". I've read some of the math, but that did little to satisfy me (I need to study it more clearly). But all of this seems in a tragic state at the moment. Allowing rampant misinformation and hype as to what these machines are actually capable of.
I'm going to butcher a lot of the physics here, but here's the gist of it that should avoid some quantum myths: The quantum state of a system is not described by a simple real probability but by a complex number. This means that there is an additional degree of freedom that you can adjust in a quantum state that doesn't change its probability of occurring. The nature of entanglement means that there is constructive a…
OK, yes. This builds on the parts of my intuition that already exist. It's about building a system (from combinations of quantum operators) that maximizes the probability distribution of the result you want. I'm still unsure of the timeline of any quantum operator, and the "finding the interference" seems equivalent to saying something like "find the function" or something more classical.
Re: The Case Against Quantum Computing
#20Earlier quoted context omitted.
With one major difference. We know that fusion in some form is possible (for example, in the sun, or in a hydrogen-bomb). The difficulty is doing it at a reasonable scale. It's less clear that quantum computing is possible.
I mean we already have quantum computers too. https://quantumexperience.ng.bluemix.net/qx/experience The trouble here is also scaling, but in the upward direction.
The "quantum computers" we have are classical computers with very weird hardware. The thing everybody is trying to achieve is quantum supremacy - this hasn't been achieved or demonstrated yet, and might never will be.