Abhay Ashtekar
Pennsylvania State University

The many faces of photons

In the standard Fock representation, the 1-photon Hilbert space is spanned by positive frequency, source-free solutions of Maxwell’s equations. The quantum information they carry corresponds precisely to the two radiative modes of the Maxwell fields.  However, this Fock representation is inadequate in a number of physical situations involving sources, and one then has to use appropriate non-Fock representations. I will focus on the ones that are of relevance to quantum optics and  quantum information. In these representations, photons can carry additional, Coulombic information. One can devise experiments to read it.