41–50 of 237 posts
The ability to entangle particles feels like a really amazing new capability. (New in the last 100 years anyway). Like it’s a brand new kind of substance that has never been made before. Everything in all of history has been built out of boring old atoms, not these fancy new entangled things. Even if quantum computers turn out not to be able to solve interesting problems, I wonder if computers are the only thing we c…
Dumb question: Say I have a wooden stick and I break it in half in less than a second. Assume a computer would need several minutes to simulate everything that would've happened in the stick. I clearly got the output faster than a computer (and with more precision), so does this imply I'm doing anything particularly fascinating? I assume the same scenario is possible to concoct for a quantum computer. I assume it wou…
When you break a stick you just break a stick. When you simulate breaking a stick you know everything about the broken stick. What if you broke the stick to study its material properties? Then you would need to spend months carefully taking samples and measuring all the broken spots. With a perfect simulation? You're done the moment it ends. All the data is there available with a copy paste
As far as I understand, to perfectly simulate reality, you would need a second reality.
Earlier quoted context omitted.
If it is able to break crypto then surely that means it can do other "interesting" mathematical calculations that are currently extremely slow/hard though?
Possibly. This is way beyond my knowledge. But I'm not aware of many other "search this finite part of the number line for this property", where "this finite part" is still too big for classical computers. It almost sounds like quantum computers are tailor made for the types of problems we've been building cryptosystems on. But maybe this is not all quantum computers will be able to do. I couldn't even explain exactl…
"This is a very nice demonstration of quantum advantage. While a great achievement academically, the algorithm used does not really have real world practical applications, though." Not having real world applications is not necessarily damning, of course. Curious to know what implications this has for general algorithms. Reading this, it almost makes it sound like there will be some algorithms that quantum is better a…
This is exactly correct. While you can simulate classical computations on a quantum computer, it doesn't make a lot of sense to. However, there exists a class of problems for which there exist solutions that have lower time complexities than anything we can run on a classical computer, if only we had a quantum computer of sufficient size.
Examples of such algorithms are the famous two, Shor's and Grover's algorithms, of which Shor's is more interesting because it factors integers in polynomial time whereas the best known classical algorithm runs in exponential time (this is the one that's scary for cryptography). Grover's algorithm is basically function inversion (find the x given a function f and some desired value y such that f(x)=y) in O(sqrt(N)) over the domain of the function, which on a classical computer requires O(N) operations.
Those were discovered in the 90's, so they're pretty widely understood by now. There's a few newer ones, such as the quantum algorithm for linear systems of equations, which solves for a scalar result of an operation applied to the unknown vector x such that Ax=b in O(log(N)k^2) time versus the classical O(nk), where n is the number of matrix elements and k is a measure of how sensitive to error the problem is.
Basically, there's a handful of useful algorithms, and another dozen or so theoretically interesting ones, that can run faster on a quantum computer. For everything else, there's zero advantage to using one.
Dumb question: Say I have a wooden stick and I break it in half in less than a second. Assume a computer would need several minutes to simulate everything that would've happened in the stick. I clearly got the output faster than a computer (and with more precision), so does this imply I'm doing anything particularly fascinating? I assume the same scenario is possible to concoct for a quantum computer. I assume it wou…
Yes, you can write down a problem inspired by a specific stick. And yes, the written down problem will of course inevitably differ in the details from the real stick. Normally you'd think of these small differences as small errors in the description. But as soon as you try to argue the stick is computing the written-down problem, they become errors in the stick because they affect its ability to implement the problem you wrote down.
"This is a very nice demonstration of quantum advantage. While a great achievement academically, the algorithm used does not really have real world practical applications, though." Not having real world applications is not necessarily damning, of course. Curious to know what implications this has for general algorithms. Reading this, it almost makes it sound like there will be some algorithms that quantum is better a…
In fact, nobody yet really knows what those problems are. There are a few real-world problems that quantum computers could theoretically help with, like factoring large numbers, but nobody is really all that close to implementing them. There are problems that can be implemented, like this one, but they are of no use whatsoever. They just happen to be feasible to implement.
The implementation does suggest that they're building up a toolbox of physical parts that could some day (years, less than decades) be used on real-world problems. The class of such problems appears very small so far, but there is reason to think that we could find other problems that matter. (For example, in the realm of AI, which is very compute-intensive -- though thus far nobody seems to have any specific implementation.)
Think of a quantum computer as a magic box on the side that solves a few problems. If you had it, you might completely reconsider what kinds of problems you want to solve. Solving it via the magic box might require a complete reconsideration of how you frame the question -- like discovering a wormhole that lets you get from Atlanta to Seattle instantly, so how would you redesign a trip from New York to LA?
Google's and IBM's previous "quantum supremacy" demonstrations were quickly crushed by improved classical simulations. Let's see if it survives this time.
I'm not saying they suck, but to proclaim that "quantum computers are superior" you need an actual use-case, IMO.
The cited paper[1] references "random circuit sampling" which is defined in [2] which then gets so heavy into abstract math, and I give up. Can someone explain this in terms an EE or programmer can understand? [1] https://arxiv.org/abs/2304.11119 [2] https://arxiv.org/abs/2007.07872
Unfortunately not. The physicists who are behind quantum computing don't think the same way, and go straight for the abstract math to solve any problem. I am pretty sure they don't understand that most of our progress on computing up to this point is because you don't need to go into Galois fields or discrete math to describe what a computer or algorithm does. I'm also pretty sure that they don't know of another way to think about it.