
My 5-minute quantum computing talk at the White House - sndean
http://www.scottaaronson.com/blog/?p=2943
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weinzierl
> I like to say that a fast classical factoring algorithm might collapse the
> world’s electronic commerce, but as far as we know, it wouldn’t collapse the
> polynomial hierarchy!

This is my favourite quote because it sums up pretty nicely the most common
misconceptions people have about factorization, crypto and quantum computing.
Of course the first part is hyperbole, but still put very nicely.

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joaorico
I liked the '10 second' explanation on what quantum computing is that Scott
gave some time ago, a propos the Justin Trudeau incident [0]. And here's other
experts' '35 seconds' versions besides Trudeau's [1].

[0]
[http://www.scottaaronson.com/blog/?p=2694](http://www.scottaaronson.com/blog/?p=2694)

"I say something about how a QC is a proposed device that would solve certain
specific problems much faster than we know how to solve them today, by taking
advantage of quantum mechanics, which generalizes the laws of classical
probability.

Then I talk about how you’d never talk about a -20% chance of rain tomorrow,
but quantum mechanics is based on numbers called amplitudes, which can be
positive or negative or even complex numbers.

And how, if an event can happen one way with a positive amplitude and another
way with a negative amplitude, the two possibilities can “interfere
destructively” and cancel each other out, so that the event never happens at
all. And how the state of a QC with (say) 1000 bits would have one amplitude
for each of 21000 possible settings of the bits—an astronomical amount of
information, if one wanted to write it down classically, for example in order
to simulate what the QC was doing classically.

But about how, when you measure the QC’s state, you just see a single random
output (with its probability determined by its amplitude), not the gargantuan
list of possibilities. And about how the goal, in QC, is always to choreograph
things so that the possible paths leading to each wrong answer interfere
destructively and cancel each other out, (say) some having positive amplitudes
and others negative, whereas the paths leading to right answer reinforce.

And how this is a very weird and specialized capability—it’s not nearly as
simple as “trying all the answers in parallel” (if you did that, you’d simply
observe a random answer), nor is it just a smaller or faster version of
ordinary computing (a QC might even be “bigger” or “slower” than an ordinary
one; all the hoped-for advantage comes from the QC’s ability to create
interference patterns).

Finally I talk about how a QC is known to give huge advantages over any known
classical algorithm for a few tasks of practical importance (quantum
simulation, breaking almost all the crypto used today…), and it might also
give some advantages for broader goals like optimization and machine learning,
but that’s an active research topic, and if the advantages exist they’ll
probably be more modest and/or specialized."

[1] [http://www.macleans.ca/society/science/trudeau-versus-the-
ex...](http://www.macleans.ca/society/science/trudeau-versus-the-experts-
quantum-computing-in-35-seconds/)

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alva
Possibly the best place to see massive spin in action.

~~~
ccvannorman
I see what you did there.

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ome6a
I have Idea. But... who cares :)

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smaddox
"I like to say that for me, the #1 application of quantum computing—more than
codebreaking, machine learning, or even quantum simulation—is just disproving
the people who say quantum computing is impossible! So, quantum supremacy
targets that application."

\facepalm

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krastanov
Could you elaborate on why you dislike this quote? Maybe there is some context
missing: for a lot of researchers quantum computing is interesting because of
how its existence informs fundamental questions in physics and math like the
Church-Turing thesis. For those people the code breaking application are
indeed pretty boring, just like internal combustion engines can be boring for
people working on statistical physics and thermodynamics.

~~~
hnal943
Well, it's not really an application, is it? It seems like a fancy way of
saying, "the stuff I'm working on isn't good for anything - it's just to
satisfy my intellectual curiosity". Which is fine as far as it goes, but not
exactly inspiring.

~~~
krastanov
I would say for me it is the applications that are boring, not the
fundamentals behind them.

For a lot of people fundamental laws of nature are deeply inspiring,
tangentially because of a belief that those fundamental laws and their deeper
understanding bear fruit beyond our wildest imagination. Compared to this it
is easy to see how today's applications are just boring.

Sure, today's technology was yesterday's research project, but you can not
fault people for being excited more about current research than about
applications of yesterday's research.

PS: However I agree that the quoted statement was poorly phrased to convey
this sentiment. From what I know about the speaker I am fairly confident that
this is what he was trying to say.

