Emit one "lower energy" Photon and.... I am aware of apparatus capable of emitting (1) photon at a time. Suppose you emitted one "lower energy" photon, then quickly absorbed this photon? At the time the photon was emitted, B and E field(s) were created, correct? Are the B and E field(s) collapsed at the time of this single photons absorbtion? Field(s) collapsed because of no photon left to interact with them? Does the answer to this question vary according to Classical Electrodynamics or QED perspectives? Any clarification is appreciated.