Induced Coherence, Vacuum Fields, and Complementarity in Biphoton Generation

TL;DR

This paper explores how induced coherence in biphoton generation affects interference visibility, demonstrating the role of vacuum fields and complementarity through experiments and a theoretical model.

Contribution

It introduces a simplified model linking vacuum fields to induced coherence and complementarity in biphoton experiments, supported by experimental results.

Findings

High-visibility single-photon interference due to induced coherence

Reduced interference visibility with additional photon channels

Abstract

We describe spontaneous parametric down-conversion experiments in which induced coherence across two coupled interferometers results in high-visibility single-photon interference. Opening additional photon channels allows "which-path" information and reduces the visibility of the singlephoton interference, but results in nearly perfect visibility when photons are counted in coincidence. A simplified theoretical model accounts for these complementary observations and attributes them directly to the relations among the vacuum fields at the different crystals.