# Comment on "Franson Interference Generated by a Two-Level System"

## TL;DR

This paper critically examines a recent Franson interferometry experiment with quantum dot photon pairs, clarifying misconceptions about the reported visibility and its implications for Bell inequality violations.

## Contribution

It provides a detailed critique of the previous experiment's interpretation and offers corrections to accurately assess quantum correlations.

## Key findings

- The reported 66% visibility does not surpass the classical limit.
- The claim of approaching Bell inequality violation is unfounded without proper analysis.
- The paper clarifies the conditions needed for genuine Bell inequality violations.

## Abstract

In a recent Letter [Phys. Rev. Lett. 118, 030501 (2017)], Peiris, Konthasinghe, and Muller report a Franson interferometry experiment using pairs of photons generated from a two-level semiconductor quantum dot. The authors report a visibility of 66% and claim that this visibility "goes beyond the classical limit of 50% and approaches the limit of violation of Bell's inequalities (70.7%)." We explain why we do not agree with this last statement and how to fix the problem.