OPTICAL COHERENCE - A CONVENIENT FICTION

We conjecture that optical coherences, i.e., quantum-mechanical cohere nces between states separated by Bohr frequencies in the optical regim e, do not exist in optics experiments. We claim the exact vanishing of optical field amplitudes and atomic dipole expectation values, and we discuss the seemingly contradictory success of assigning finite value s to such quantities in theoretical calculations. We show that our con jecture is not at variance with the observed interference between diff erent light sources. The connection to the concept of spontaneous symm etry breaking and the identification of entangled states as pointer ba sis states is discussed.