On Wigner Functions and Quantum Dynamics on a Circle

Abstract: In the present work we consider properly defined two-parameter Wigner functions that, e.g., can be used as witness for quantum behaviour for pure states as expressed in terms of a self-adjoint observable angular position and the corresponding angular momentum operator L. It is shown that negative values of the corresponding Wigner functions may reveal the quantum nature of superpositions of angular momentum eigenstates with a fractional mean value of L but in an ambiguous manner. For a suitable choice of parameters these Wigner functions are positive and are in accordance with Borns rule in quantum mechanics.