Field representations in phase space : Wigner's Q-function and W-function

The fifth lesson described field states in phase space, introducing two important functions defined in this space, Wigner's Q-function and W-function. These functions provide a pictorial and intuitive description of Fock states, coherent states and their superpositions. The essential properties of the W function are reviewed. A general "tomographic" method for measuring this function was described. The link with the Wigner function, introduced in statistical physics as a quasi probability distribution in phase space, was recalled.