Delayed-choice quantum eraser for the undergraduate laboratory

TL;DR

This paper presents an optical delayed-choice quantum eraser experiment suitable for undergraduates, demonstrating that the timing of erasure does not affect interference, thus illustrating fundamental quantum mechanics principles.

Contribution

It introduces a practical, educational implementation of a delayed-choice quantum eraser using polarization-entangled photons with two different delay setups.

Findings

Interference fringes are observed regardless of erasure timing.

The experimental results agree with quantum mechanics predictions.

The setup is effective for teaching quantum concepts.

Abstract

In a delayed-choice quantum eraser, interference fringes are obtained by erasing which-way information after the interfering particle has already been irreversibly detected. Following an introductory review of delayed-choice experiments and quantum erasure, we describe the experimental realization of an optical delayed-choice quantum eraser, suitable for advanced undergraduates, based on polarization-entangled pairs of single photons. In our experiment, the delay of the erasure is implemented using two different setups. The first setup employs an arrangement of mirrors to increase the optical path length of the photons carrying which-way information. In the second setup, we use fiber-optic cables to elongate the path of these photons after their passage through the polarization analyzer but prior to their arrival at the detector. We compare our results to data obtained in the absence of a delay and find excellent agreement. This shows that the timing of the erasure is irrelevant, as also predicted by quantum mechanics. The experiment can serve as a valuable pedagogical tool for conveying the fundamentals of quantum mechanics.