  In quantum mechanics, photonic de Broglie waves have been understood as a
unique property of quantum mechanics satisfying the complementarity between
particle and wave natures of light, where the photonic de Broglie wavelength is
inversely proportional to the number of entangled photons acting on a beam
splitter. Very recently, the heart of nonclassical feature of photon bunching
on a beam splitter was newly interpreted using pure wave nature of coherence
optics [arXiv:1911.07174v2], paving a road to unconditionally secured classical
key distribution [arXiv:1807.04233v3]. Here, Mach-Zehnder interferometer-based
deterministic photonic de Broglie waves are studied in a coherence regime for
both fundamental physics and potential applications of coherence-quantum
metrology.
