Near-field optics and quantum optics: an assignation arranged by four kinds of photons

In the process of emergence a photon emitted from an atom (or a molecule) is usually no better localized in space than to the near-field zone of the source. Near-field optics therefore is of central importance for understanding fundamental statistical aspects related to single-photon tunnelling, the space-time description of photon dynamics, and the photon position-operator problem. In the present work an attempt is made to study the microscopic near-field optical interaction from a quantum statistical point of view. In near-field quantum electrodynamics (QED) scalar and longitudinal photons always are involved and this makes the covariant formulation of QED attractive also in the low-energy regime. We show that the Lorenz gauge condition on the global state vector relates to the near-field electrodynamics of the d-photons. The gauge photon is shown to be of no importance in near-field interactions. To understand the role of the lack of photon localizability we finally study near-field quantum optical correlations in a new so-called propagator gauge.