Coherently induced quantum correlation in a delayed-choice scheme

Quantum entanglement is known as a unique quantum feature that cannot be obtained by classical physics. Recently, coherence interpretations of the quantum correlation have been presented for Franson-type correlation and delayed-choice quantum eraser, where coherence understanding of the basis-product superposition is the key to the quantum correlation. Here, coherence manipulations of the basis-product superposition between paired coherent photons are presented for the quantum feature in a delayed-choice scheme, whose quantum feature is represented by a joint-phase relation of local parameters. Such a coherently excited quantum feature is the heart of the Bell inequality violations for the nonlocal quantum correlation between space-like separated quantum particles.