On Quantum States for angular Position and Angular Momentum of Light

Abstract

In the present paper we construct a properly defined quantum state expressed in terms of elliptic Jacobi theta functions for the self-adjoint observables angular position $\theta$ and the corresponding angular momentum operator $L = -id/d\theta$. The quantum uncertainties $\Delta \theta$ and $\Delta L$ for the state are well-defined and are, e.g., shown to give a lower value of the uncertainty product $\Delta \theta \Delta L$ than the minimal uncertainty states of Ref.\cite{Padgett_2004}. The mean value $< L >$ of the state is not required to be an integer. In the case of any half-integer mean value $< L >$ the state constructed exhibits a remarkable critical behavior with upper and lower bounds $\Delta \theta < \sqrt{\pi^2/3 -2}$ and $\Delta L > 1/2$.