Pauli gates (X, Y, Z)

Each of these gates rotates the qubit they act on by 180 degrees. The rotation of the X gate is about the x axis, the rotation of the Y gate is about the y axis, and the rotation of the Z gate is about the z axis.

In Python, these gates are defined as follows:

X=np.matrix('0 1; 1 0')
Y=np.matrix([[0, -i_],[i_, 0]])
Z=np.matrix([[1,0],[0,-1]])