  Photonic de Broglie waves (PBWs) via two-mode entangled photon pair
interactions on a beam splitter show a pure quantum feature which cannot be
obtained by classical means1-4. Although PBWs have been intensively studied for
quantum metrology5-13 and quantum sensing14-25 over the last several decades,
their implementation has been limited due to difficulties of high-order NOON
state generation4. Recently a coherence version of PBWs, the so-called
coherence de Broglie waves (CBWs), has been proposed in a pure classical regime
of an asymmetrically coupled Mach-Zehnder interferometer (MZI)26. Unlike PBWs,
the quantumness of CBWs originates from the cascaded quantum superposition of
the coupled MZI. Here, the first CBWs observation is presented in a pure
classical regime and discussed for its potential applications in coherence
quantum metrology to overcome conventional PBWs limited by higher-order
entangled photons. To understand the quantum superposition-based nonclassical
features in CBWs, various violation tests are also performed, where
asymmetrical phase coupling is the key parameter for CBWs.
