Readings

 The Pauli matrices, and  Bloch sphere, belong to the realm of Quantum Physics. 

The X, Y, and Z gates are artefacts of Quantum Computing. The use-value of these

gates can be different for different computer architectures, or the types of computing

problems envisaged. Qiskit, for example, only measures in the Z computational  basis;

that is, only tells us whether a qubit is up or down. One can, nonetheless, develop

algorithms that are based on phase changes, with 'the proof in the pudding' . Below,

the movements occasionned by these three fundamental gates. The other gates in play

can be understood with reference to these.

The X-gate:

                                                                                        

*     *     *

The Y-gate:

*     *     *

The Z-gate:

                                                                

                                                                    *     *     *

 X movement:      

                                                                           

                                 

Y movement:

                                                                                  

      
                                                                      

Z movement (from Hadamard):