Complementarity in Biphoton Generation with Stimulated or Induced Coherence

TL;DR

This paper compares induced and stimulated coherence in biphoton generation, revealing distinct interference behaviors and phase correlations, with experimental results supported by a simplified theoretical model.

Contribution

It provides a direct experimental comparison of induced and stimulated coherence effects in biphoton generation, highlighting their differences and phase relationships.

Findings

Different interference patterns observed in induced vs. stimulated coherence.

Insertion of a transmission filter affects the coherence differently in each case.

A theoretical model explains all experimental results and addresses phase correlation questions.

Abstract

Coherence can be induced or stimulated in parametric down-conversion using two or three crystals when, for example, the idler modes of the crystals are aligned. Previous experiments with induced coherence [Phys. Rev. Lett. 114, 053601 (2015)] focused on which-path information and the role of vacuum fields in realizing complementarity via reduced visibility in single-photon interference. Here we describe experiments comparing induced and stimulated coherence. Different single-photon interference experiments were performed by blocking one of the pump beams in a three-crystal setup. Each counted photon is emitted from one of two crystals and which-way information may or not be available, depending on the setup. Distinctly different results are obtained in the induced and stimulated cases, especially when a variable transmission filter is inserted between the crystals. A simplified theoretical model accounts for all the experimental results and is also used to address the question of whether the phases of the signal and idler fields in parametric down-conversion are correlated.