  In a $\Lambda$ system with two nearly degenerate ground states and one
excited state in an atom or quantum dot, spontaneous radiative decay can lead
to a range of phenomena, including electron-photon entanglement, spontaneously
generated coherence, and two-pathway decay. We show that a treatment of the
radiative decay as a quantum evolution of a single physical system composed of
a three-level electron subsystem and photons leads to a range of consequences
depending on the electron-photon interaction and the measurement. Different
treatments of the emitted photon channel the electron-photon system into a
variety of final states. The theory is not restricted to the three-level
system.
