
It’s Time to Learn about Quantum Computing - f3f3_
https://www.wired.com/story/time-you-learned-about-quantum-computing
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ivan_ah
Here is a shameless plug to my book on linear algebra that comes with an
introduction to quantum mechanics (Chapter 9):
[https://www.amazon.com/dp/0992001021/noBSLA](https://www.amazon.com/dp/0992001021/noBSLA)

If you know you linear algebra well, learning quantum mechanics is not so
complicated, see the book preview here:
[https://minireference.com/static/excerpts/noBSguide2LA_previ...](https://minireference.com/static/excerpts/noBSguide2LA_preview.pdf#page=125)

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graycat
One of the collections of current practical problems frequently and
continually mentioned as big reasons for developing quantum computers is
combinatorial optimization. Right, these problems are commonly in the class
NP, and that means that so far, as problem size grows, the guaranteed
sufficiently large time and or space on a current, classic digital computer to
get optimal solutions of worst case problems grows like an exponential in the
problem size.

But practical problems don't need to be so large; approximately optimal
solutions might save 90% of the money of optimal solutions and very valuable;
real problems commonly are not much like the worst case problems; and we long
had lots of methods for combinatorial optimization that do quite well in
practice.

Point: If practical problems in combinatorial optimization are of interest,
then bring them forward -- they've been coming forward mostly only rarely.
Else, let's find other reasons for pressing forward with quantum computers.

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lomnakkus
Per Wikipedia isn't not actually known whether quantum computers will be able
to solve NP-complete problems in polynomial time:

> There is a common misconception that quantum computers can solve NP-complete
> problems in polynomial time. That is not known to be true, and is generally
> suspected to be false.[120]

The citation is from 1997, but I seem to remember that someone came up with a
proof sometime in the last decade...? Probably just my faulty memory rather
than the Wikipedia being out of date.

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abdullahkhalids
There is no known proof of separation between BQP and NP.

See [https://en.wikipedia.org/wiki/BQP](https://en.wikipedia.org/wiki/BQP) for
the relation of BQP to other complexity classes.

~~~
lomnakkus
Ah, thanks.

(I was actually looking at the BQP page,, but then realized that I know far
less about the _Q_ classes than I should and found the more general "quantum
computing" page where my citation is from.)

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GChevalier
So many ads and things that prompt for attention on this page! I needed to
press "x" on 3 things to be able to read. And once read to the end, it refers
to a "video above" that won't open under Chrome for mobile. Wired, calm down
on crap!

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stephengillie
You're not missing much in this 304-word blurb. Outside of name-dropping,
there's an introductory snippet that guides you to a video.

> _So how do they work? You may have heard that the normal rules of reality
> don’t always apply in the world of quantum mechanics. A phenomenon known as
> a quantum superposition allows things to kinda, sorta, be in two places at
> once, for example. In a quantum computer, that means bits of data can be
> more than just 1 or 0, as they are in a conventional computer; they can also
> be something like both at the same time.

When data is encoded into effects like those, some normal limitations on
conventional computers fall away. That allows a quantum computer to be much
faster on certain tricky problems. Want a full PhD, or third-grade,
explanation? Watch the video above._

