
Quantum Machine Learning: An Overview - rbanffy
https://www.kdnuggets.com/2018/01/quantum-machine-learning-overview.html?utm_content=buffercca0b&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer
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ignoranceprior
On the other hand, see "Quantum Machine Learning Algorithms: Read the Fine
Print" by Scott Aaronson:

[https://www.scottaaronson.com/papers/qml.pdf](https://www.scottaaronson.com/papers/qml.pdf)

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vtomole
True. It's too early to say whether or not quantum computers will practically
outperform classical computers on machine learning tasks or any task at all.

Like Shor's factoring and Grover's algorithm, machine learning problems like
solving systems of linear equations have been mathematically proven to have a
quantum speedup. The problem is engineering quantum computers well enough that
they can outperform classical computers on these tasks. We are currently
working on that and it will take a couple of decades at least.

Hope is not lost. There are also a couple of theories that hybrid
classical/quantum computers of the next decade or so will perform some tasks
like quantum chemistry and approximate optimization (which can be used in
machine learning) better than classical computers. Only time will tell.

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moefh
> solving systems of linear equations have been mathematically proven to have
> a quantum speedup

I'm not an expert, so please correct me if I'm wrong, but my understanding
from Aaronson's paper is that this is not really true in general.

Unlike Shor's algorithm, which can be used to actually find the factors of
some integer, HHL (the quantum algorithm that "solves" systems of linear
equations) is best compared to quantum Fourier transform. That is: it can only
be used to prepare a state |x> that contains the solution you want. But that's
still a quantum state -- if you naively try to measure it, you'll get garbage.
That doesn't mean HHL or quantum Fourier transform are useless (indeed,
quantum Fourier transform is used by Shor's algorithm), it just means that
they're not drop-in replacements for their classical counterparts (like Shor's
algorithm is for classical factoring).

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vtomole
That's right. HHL doesn't find x for Ax = b. It finds the result of a scalar
measurement on x. Like you said, a garbage result is generated if the state is
measured naively.

It's rare for quantum algorithms to be drop-in replacements for classical
problems. Take Grover's algorithm. Using it to search a classical database
kills the speedup due to the number of calls to memory. Therefore, it will
probably be used to attack NP-complete problems instead.

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laretluval
> They take every path in the corn maze simultaneously

I stopped reading here. Can anyone who read beyond this tell me if the article
is worth reading?

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dfan
If you have enough knowledge of quantum computation to be annoyed by that
sentence, you will not get anything out of the rest of the article.

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dkural
Quantum computing DOES NOT WORK by taking every path simultaneously. This is
an incredibly misleading analogy.

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nixpulvis
I wish I could have all the time I've spent reading articles like this back...

