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An Introduction to Quantum Computing, Without the Physics (arxiv.org)
149 points by lainon on Aug 15, 2017 | hide | past | favorite | 18 comments


The article on QC I got the most out of: http://www.scottaaronson.com/blog/?p=208

Very visual example of how Shor's algorithm works to solve factoring. Nothing more than basic arithmetic required.

The big takeaway for me was, it's not just "try every combination at once" as per pop lit on the subject. QC doesn't really do that. To get QC to work any better that traditional for any task, you need to get lucky and stumble across an algorithm that QC can excel at for that task. Just from reading Scott Aaronson's article, it seems likely that most tasks simply don't have a QC optimization, so perhaps QC won't change much at all. (Well, except cryptography, which may change everything...)


Yes, this was a bit of a surprise for me to - "In fact, in general solving NP-hard problems in polynomial time with quantum computers is not believed to be possible"


Consider these two simulators, if you want to try the examples in the paper:

1. https://www.research.ibm.com/ibm-q/

This is IBM Quantum experience. Click on "experiment" to start. It has a nice tutorial.

2. http://algassert.com/quirk

I like this one much better, because you can see the internal state of the machine at any moment. And it has much more options and is much faster.


After quickly skimming it it seems well done. Leans towards mathematical rigor, which may not be ideal for some people. On the other hand, it'd be pretty hard to avoid math: quantum computing is linear algebra incarnate.

The only thing that caught my eye as off was totally minor. They say the many-controlled-Z gate used by Grover's algorithm can be done in O(n^2) constant-sized gates with an argument-by-reference, but with that type of argument you might as well give the tight bound of Θ(n).


It's possible to have a gentle ramp-up on the math content while learning quantum mechanics. "The Theoretical Minimum" by Susskind and Hrabovsky is structured like that: They teach you the math as part of, and motivated by, teaching the physics, and the books don't lag or resort to hand-waving.

https://en.wikipedia.org/wiki/The_Theoretical_Minimum


Note: Susskind has a follow up - Quantum Mechanics: The Theoretical Minimum.

https://www.goodreads.com/book/show/18210750-quantum-mechani...


I should have been clearer that I was referring to both books in the series with my remarks.


Thanks for this, I have been looking for a good introduction to Quantum Computing. I haven't actually read it yet, but this looks promising.


I've recommended this here before, but David Mermin's "Quantum Computer Science: An Introduction" is also good (like this paper, it's targeted at computer scientists who have a little math knowledge and little-to-no physics background). There's a dead-tree version, but the lecture notes the book is based on are available online: http://www.lassp.cornell.edu/mermin/qcomp/CS483.html


I've been meaning to get into it but someone recommended me this series on youtube https://www.youtube.com/watch?v=X2q1PuI2RFI&list=PL1826E60FD...


Quantum Computation and Quantum Information by Nielsen and Chuang is the standard introduction to quantum computing. Besides that, you can find some old CS191 Vazirani lectures on the internet.


Here is a medium post targeted at layperson that covers a lot of same material. "Quibbling Over Qubits" https://medium.com/@_NicT_/quibbling-over-qubits-f2ca1b87f47...



r/QuantumComputing[1] is a great place if you want to learn more. We read and discuss one Quantum Computing paper a week.

[1]https://www.reddit.com/r/QuantumComputing/


Consider also "Quantum Computing Explained" by McMahon.


Hope I am retired before it's mainstream :)


> Without the Physics

Well, is there much "physics" in (theoretical) quantum physics anyway? It's pretty much all math - just like in this paper!


Maths doesn't have to agree with physical experiments and observation.




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