Pulsed Rabi oscillations in quantum two-level systems: beyond the Area Theorem

TL;DR

This paper explores the limitations of the Area Theorem in quantum two-level systems, combining analytic modeling and experimental measurements to understand deviations in photon emission dynamics, especially two-photon events, beyond ideal short pulse conditions.

Contribution

It introduces a simple quantum trajectory model that explains the breakdown of the Area Theorem and demonstrates its validity through experiments with semiconductor quantum dots.

Findings

Model accurately predicts photon emission statistics for short pulses.

Experimental results confirm the model's explanation of two-photon emission dominance.

Re-excitation mechanisms are clarified, explaining deviations from ideal Rabi oscillations.

Abstract

The Area Theorem states that when a short optical pulse drives a quantum two-level system, it undergoes Rabi oscillations in the probability of scattering a single photon. In this work, we investigate the breakdown of the Area Theorem as both the pulse length becomes non-negligible and for certain pulse areas. Using simple quantum trajectories, we provide an analytic approximation to the photon emission dynamics of a two-level system. Our model provides an intuitive way to understand re-excitation, which elucidates the mechanism behind the two-photon emission events that can spoil single-photon emission. We experimentally measure the emission statistics from a semiconductor quantum dot, acting as a two-level system, and show good agreement with our simple model for short pulses. Additionally, the model clearly explains our recent results [K. Fischer and L. Hanschke, et al., Nature Physics (2017)] showing dominant two-photon emission from a two-level system for pulses with interaction areas equal to an even multiple of $\pi$.