switching left and right

[neeco1991]

Closes #4414.

The text says:

Other allowed labels include "+" and "-" for the plus and minus states, as well as "r" and "l" (short for "right" and "left") for the states:

And then proceeds defining the "r" state on the left, and the "l" state on the right, which might be confusing. I suggest to write the "l" state on the left and the "r" state on the right.

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[jlapeyre]

@neeco1991 I agree with you. Although it took me a while to understand what the problem is, once I saw it, I also think it could be confusing.

However, since this is a tutorial, making it even more clear would be useful. Something like:

The label "l" refers to $|-i\rangle$, the $-1$ eigenstate of the operator $Y$. Likewise "r" refers to the $+1$ eigenstate of $Y$. In the $Z$-basis, these are...