Photon angular momentum and zero-point oscillations

Abstract Radiation from certain oscillating charge distributions can have angular momentum that cannot be explained in classical electrodynamics. We consider the angular momentum of a single-photon field from an electric dipole oscillator and in particular compare the classical and quantum expressions for the mean-square field angular momentum. We show that differences in these expressions are attributable to zero-point oscillations of unexcited states of the dipole oscillator.