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- 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?

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?