Polarization state
= Polarization state
The <quantum state> associated with the two transverse polarization degrees of freedom of a photon in a specified propagation mode. In a horizontal-vertical basis, a pure state is $\alpha|H\rangle+\beta|V\rangle$ with $|\alpha|^2+|\beta|^2=1$; a <density matrix> also describes mixtures. Linear polarizers test real combinations of these basis states, while phase-sensitive elements allow elliptical and circular polarization measurements.