I Confusions about some symbols in QC

[Haorong Wu]

TL;DR 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?

 

[DrClaude]

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]

So, should there be lines crossing those squares?

No. You can see correct examples on Wikipedia:
https://en.wikipedia.org/wiki/Quantum_logic_gate

 

[Haorong Wu]

No. You can see correct examples on Wikipedia:
https://en.wikipedia.org/wiki/Quantum_logic_gate

Thanks DrClaude. I got to learn to search on wikipedia first.