Direct measurement of the Wigner time-delay for the scattering of light by a single atom

TL;DR

This paper experimentally measures the Wigner time-delay in light scattering by a single atom, revealing delays up to 42 nanoseconds at resonance, which is significant for understanding collective scattering phenomena.

Contribution

First direct measurement of the Wigner time-delay for light scattering by a single atom, demonstrating the delay's dependence on light frequency.

Findings

Measured delays up to 42 nanoseconds at resonance

Delay limited by the excited state's lifetime

Highlights importance for collective scattering studies

Abstract

We have implemented the gedanken experiment of an individual atom scattering a wave packet of near-resonant light, and measured the associated Wigner time-delay as a function of the frequency of the light. In our apparatus the atom behaves as a two-level system and we have found delays as large as 42 nanoseconds at resonance, limited by the lifetime of the excited state. This delay is an important parameter in the problem of collective near-resonant scattering by an ensemble of interacting particles, which is encountered in many areas of physics.