
An Explanation of Shor's Quantum Factoring Algorithm - Strilanc
http://algassert.com/post/1718
======
metalliqaz
Good article. Definitely helped fill me in on this stuff, although I still
have too many questions about how the underlying physics work to feel like I
understand it.

This article contains the sentence, "A good predictor for whether you even
slightly understood that last sentence is whether or not your mind just got
blown hard." It blew my mind, but mostly because I'm just amazed that there
are people who are capable of engineering this kind of chaos into something
useful. Not sure if that's what he meant.

I would really like to get a handle on all this, but I'm thinking now that I
would have to retire to do so.

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hondadriver
Maybe relevant:
[https://www.scottaaronson.com/blog/?p=208](https://www.scottaaronson.com/blog/?p=208)

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phoenixstrike
I get that these kind of posts can seem interesting to the software engineers
that are predominant on HN, but these kind of articles are ultimately "popular
science" articles. They only give the illusion of understanding.

I'm tired of people trying to find or make shortcuts to advanced topics. If
you want to truly understanding something, put in the work. Shor's actual
paper for this is only 25 pages. You need a strong background in advanced
linear algebra and quantum theory to understand it. If you don't know quantum
theory and linear algebra, you are fundamentally incapable of understanding
Shor's algorithm. It's like trying to understand how compound interest works
in finance without understanding what multiplication is. There's no point, you
shouldn't even try. It's wasted time, and anyone who says otherwise is missing
the point.

If you're serious about wanting to understand advanced topics, put in the damn
work. Stop trying to find or make shortcuts. Shortcuts only produce a bunch of
know-it-all armchair scientists that think they understand something just
because they read a blog post about it. People spend their entire lives
studying these topics. Are you so presumptuous?

Don't get me wrong, analogies and novel perspectives can be invaluable
learning tools. But they can never be a substitute for the fundamentals, only
supplement them.

Anyway, I apologize for the rant. The author is clearly interested in QI and
has put a lot of effort into his articles. That is to be applauded. But I
caution anyone reading this, or any other article on QI, to be aware of the
fact that he or she is reading a shortcut and should not believe that he or
she has actually understood Shor's algorithm.

~~~
bemeurer
OP mentions on the post how it's a simplified explanation. I don't think he's
trying to write a textbook on Shor's algorithm here.

Also, a subject's complexity is no excuse to not try and explain it in an
accessible way. I find it far-fetched that someone would read a blog post on
QC and then assume they're a specialist; and if they do it's not the author's
fault. Articles like this help present the field to non-specialists, it allows
people to have a basic understanding of Shor's without having to go through
years of education/training.

Finally, saying "these kind of articles are ultimately "popular science""
makes me question whether you actually put in the work to read this.

~~~
phoenixstrike
I agree with your general sentiment regarding making advanced topics
accessible. But since you proof-read the article, I hope you are not
suggesting that knowledge of Hadamard gates should be considered as
"accessible."

In any case, the main reason why I think of this article as "popular science"
is because it fails to even attempt to explain quantum fourier transforms in
layman's terms. The author even admits that such an explanation is beyond the
scope of the article and instead uses the analogy of audio signal processing
to draw an analogy between audio signals and QFT, hand-waving at some
connection between the two solely by virtue of the fact that both use Fourier
transforms. I am sorry, but I have seen this cliche way too many times--that
quantum physics and music/audio are somehow intertwined and can be used as
analogies for each other, just because of the fact that both can be described
as waves? In the end, the most essential part is left unexplained, and only a
vague analogy with a more familiar system (audio) is drawn, leaving only an
imprint of false understanding. Popular science.

Since QFT is a prerequisite for quantum factoring, in my opinion this article
does not explain a thing. Sure, people may become more interested in QI after
reading this article, but in that case, let's be honest about what this
article is: an advertisement, not an explanation. Show me a macroscopic system
that exhibits true wave-particle duality and can be used as an analogy for
quantum systems, then I'll take it seriously.

~~~
LolWolf
>Show me a macroscopic system that exhibits true wave-particle duality and can
be used as an analogy for quantum systems, then I'll take it seriously.

With the "true" in that sentence, we might be dealing with some moving
goalposts, but this[0] is a well-known classical system which behaves
similarly to a Bohmian description of QM and also exhibits interference, etc,
on double-slit experiments.

\-----

[0] [https://arxiv.org/pdf/1401.4356.pdf](https://arxiv.org/pdf/1401.4356.pdf)

