Spectroscopic test of Bose-Einstein statistics for photons

TL;DR

This paper tests the fundamental Bose-Einstein statistics for photons by measuring forbidden two-photon transitions in atomic barium, setting a new stringent limit on violations and observing hyperfine interactions enabling forbidden transitions for the first time.

Contribution

It provides the most precise limit to date on violations of Bose-Einstein statistics for photons and reports the first observation of hyperfine interaction enabling forbidden transitions.

Findings

Limit on violation rate: ν<4.0×10^{-11} at 90% confidence

First observation of hyperfine interaction enabling forbidden transition

Over three orders of magnitude improvement over previous results

Abstract

Using Bose-Einstein-statistics-forbidden two-photon excitation in atomic barium, we have limited the rate of statistics-violating transitions, as a fraction $\nu$ of an equivalent statistics-allowed transition rate, to $\nu<4.0\times10^{-11}$ at the 90% confidence level. This is an improvement of more than three orders of magnitude over the best previous result. Additionally, hyperfine-interaction enabling of the forbidden transition has been observed, to our knowledge, for the first time.