  In this article, we present a unified reciprocal quantum electrodynamics
(QED) formulation of quantum light-matter interaction. For electron-light
interactions, we bridge the underlying theories of Photon-Induced Near-field
Electron Microscopy (PINEM), Laser-induced Particle Accelerators and radiation
sources, such as Free Electron Laser (FEL), transition radiation and
Smith-Purcell effect. We demonstrate an electron-photon spectral reciprocity
relation between the electron energy loss/gain and the radiation spectra. This
"Acceleration/Radiation Correspondence" (ARC) conserves the electron-energy and
photon-number exchanged and in the case of a Quantum Electron Wavepacket (QEW),
displays explicit dependence on the history-dependent phase and shape of the
QEW. It originates from an interaction-induced quantum interference term that
is usually ignored in Fermi's Golden Rule analyses. We apply the general QED
formulation to both stimulated interaction and spontaneous emission of
classical and quantum light by the quantum-featured electrons. The
'spontaneous' emissions of coherent states ('classical' light) and squeezed
states of light are shown to be enhanced with squeezed vacuum. This reciprocal
ARC formulation has promise for extension to other fundamental research
problems in quantum-light and quantum-matter interactions.
