  Over the last several decades, entangled photon pairs generated from
\c{hi}^((2)) nonlinear optical materials via spontaneous parametric down
conversion processes have been intensively studied for various quantum
correlations such as Bell inequality violation and anticorrelation. In a
Mach-Zehnder interferometer, the photonic de Broglie wavelength has also been
studied for quantum sensing with an enhanced phase resolution overcoming the
standard quantum limit. Here, the fundamental principles of quantumness are
investigated in an interferometric scheme for controllable quantum correlation
not only for bipartite entangled photon pairs in a microscopic regime, but also
for macroscopic coherence entanglement generation.
