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I started working in Qiskit, and here is an example of how gates of a circuit are represented graphically in LaTeX format:
Obviously, $R_y(\theta)$, is a y rotation by a certain angle. But all the other gates look like $U_i(x,y,z)$, and I don't know how what they actually do. What is their matrix representation? What do the numbers $i,x,y$ and $z$ mean?