maybe i'm missing something here, but could we not have just used a stick on the ground and rotated it accordingly, and still end up with the same result - if the stick ends up perpendicular to the plane, i.e. you? Why do we need the light polarization setup?
Hey - you totally could to mock this exact setup like you're suggesting. However, in a real quantum computer setup you would take one qubit and apply either the positive or negative rotation gate to it again and again and rotate the state of that qubit. The "stick" in the quantum computer would be the qubit (or photon in this case). So the post is meant to show what would happen in a real setup. Hope that makes sense.
