# I Confusions about some symbols in QC

#### Haorong Wu

Summary
Confusions about some symbols in QC
There are some pictures in Nielsen's book that I find confusing:

Why there is a line half-crossing the X-box?

Similarly, why there is a line connecting to $f \left ( x \right )$?

There are two H gates between $\left | \psi _0 \right >$ and $\left | \psi _1 \right >$. Why one of them has a line crossing it, while the other one only has a line half-crossing it?

Similarly, why the H gates have no lines crossing them in this picture? In the "Nomenclature and notation" section, the quantum gates are all crossed by lines. What's the differences between them?

Well, if there are just several inconsistent pictures, I would say the book has some errors. But I find there are pretty much strange appearances. Maybe I overlook some important part about those lines?

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#### DrClaude

Mentor
These are just "typographical" error. The figures appear to have been done in LaTeX, so it may just be a problem of how they were rendered for the book.

#### Haorong Wu

These are just "typographical" error. The figures appear to have been done in LaTeX, so it may just be a problem of how they were rendered for the book.
(@.@).....Ah..All right. So, should there be lines crossing those squares?

#### DrClaude

Mentor
So, should there be lines crossing those squares?
No. You can see correct examples on Wikipedia:

#### Haorong Wu

No. You can see correct examples on Wikipedia:
Thanks DrClaude. I got to learn to search on wikipedia first.

"Confusions about some symbols in QC"

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