Erasing the which-path information of photons

TL;DR

This paper investigates multidimensional which-path information in nested Mach-Zehnder interferometers, introduces a general expression, demonstrates control via phase and beam splitters, and predicts a new elimination phenomenon with experimental validation.

Contribution

It provides a comprehensive expression for which-path information, explores its controllability, and predicts a novel elimination phenomenon with experimental confirmation.

Findings

Derived a general expression for which-path information.

Showed control of which-path information via phase and beam splitter adjustments.

Predicted and experimentally demonstrated a new elimination phenomenon.

Abstract

Which-path information of a quantum particle in interferometers is the key to infer the past of quantum particle. It arises many extensive discussions including quantum complementarity and path-visibility relation. The basic of these discussions are the description, detection and control of which-path information. In this article, we focus on the investigation of multidimensional which-path information in nested Mach-Zehnder interferometer. A general expression of which-path information is given and can be partially extracted by different detection method. Further analysis shows that the which-path information can be controlled by the phase differences and beam splitting ratios between the arms of nested Mach-Zehnder interferometer. Moreover, a new which-path information elimination phenomenon has been predicted and demonstrated experimentally. Our work can help to understand the physics of quantum particles, potentially apply to quantum information process and quantum metrology.