Accessing which-path information in the absorption and emission of light by a quantum dot in a Ramsey sequence

TL;DR

This paper investigates how which-path information in a quantum dot affects light absorption and emission in a Ramsey sequence, revealing the interplay between quantum information and light-matter interactions.

Contribution

It provides a quantitative analysis of which-path information in a quantum dot during a Ramsey sequence, linking quantum correlations to measurable light interference effects.

Findings

Which-path information increases over time during the sequence.

Contrast reduction in Ramsey fringes indicates information extraction.

Experimental results agree with theoretical predictions.

Abstract

We quantify which-path information in the absorption and emission of light by a quantum dot along a Ramsey-like sequence. The quantum dot is excited by two successive classical $\pi/2$-pulses with tunable relative phase, yielding the spontaneous release of coherent superpositions of zero- and one-photon Fock states into two successive time bins. Along the sequence, the first time bin extracts information on the quantum dot energy state, behaving as a which-path detector for the Ramsey interferometer. The which-path information increases over time, and is accessed through the reduction of contrast of the Ramsey fringes. After the second pulse, the information still present in the first time bin controls the emission of coherent light into the second time bin, which is measurable through the reduction of the contrast of self-homodyne interference fringes in a Mach-Zehnder interferometer. Both measurements are in remarkable agreement with theoretical predictions. Our results quantitatively illustrate how which-path information and more generally quantum correlations impact light-matter energy exchanges in the quantum realm.