Illustration of quantum complementarity using single photons interfering on a grating

TL;DR

This study reproduces a quantum experiment with single photons, confirming that interference visibility and which-path information obey the complementarity relation, supporting the Copenhagen interpretation.

Contribution

We experimentally reproduce and verify the complementarity relation using a true single-photon interferometer with a grating, clarifying previous claims of violation.

Findings

Interference visibility and distinguishability satisfy V^2 + D^2 < 1

Experiment aligns with Copenhagen interpretation

No violation of quantum complementarity observed

Abstract

A recent experiment performed by S. S. Afshar et al. has been interpreted as a violation of Bohr's complementarity principle between interference visibility and which-path information in a two-path interferometer. We have reproduced this experiment, using true single-photon pulses propagating in a two-path wavefront- splitting interferometer realized with a Fresnel's biprism, and followed by a grating with adjustable transmitting slits. The measured values of interference visibility V and which-path information, characterized by the distinguishability parameter D, are found to obey the complementarity relation V^2+D^2=<1. This result demonstrates that the experiment can be perfectly explained by the Copenhagen interpretation of quantum mechanics.