The connection to physics can be made if we identify the operators with physical operators such as the angular momentum and the polarization angle. We have then Δ Δ ψ ψ L ^ ^ z Δ Δ ψ ψ θ θ ≥ ≥ ℏ ℏ 2 , which means that angular momentum and the polarization angle cannot be measured simultaneously with infinite accuracy. (The polarization angle can be measured by checking whether the photon can pass through a polarizing filter oriented at a particular angle, or a polarizing beam splitter. This results in a yes/no answer that, if the photon was plane-polarized at some other angle, depends on the difference between the two angles.)