Coherent Swing-Up Excitation for Semiconductor Quantum Dots

Developing coherent excitation methods for quantum emitters ensuring high brightness, optimal single-photon purity and indistinguishability of the emitted photons has been a key challenge in the past years. While various methods have been proposed and explored, they all have specific advantages and disadvantages. This study investigates the dynamics of the recent swing-up scheme as an excitation method for a two-level system and its performance in single-photon generation. By applying two far red-detuned laser pulses, the two-level system can be prepared in the excited state with near-unity fidelity. The successful operation and coherent character of this technique are demonstrated using a semiconductor quantum dot (QD). Moreover, the multi-dimensional parameter space of the two laser pulses is explored to analyze its impact on excitation fidelity. Finally, the performance of the scheme as an excitation method for generating high-quality single photons is analyzed. The swing-up scheme itself proves effective, exhibiting nearly perfect single-photon purity, while the observed indistinguishability in the studied sample is limited by the influence of the inevitable high excitation powers on the semiconductor environment of the quantum dot.