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Q: Fachverband Quantenoptik und Photonik
Q 20: QuanTour II – Multi-photon Effects & Entanglement
Q 20.3: Talk
Tuesday, March 3, 2026, 11:45–12:00, P 7
Photon Number Coherence in Two Photon Excitation — •Yusuf Karli1,2, Florian Kappe2, René Schwarz2, Doris Reiter3, Vikas Remesh2, and Gregor Weihs2 — 1University of Cambridge, UK — 2Universität Innsbruck, Austria — 3TU Dortmund, Germany
Semiconductor quantum dots are prime candidates for single-photon sources in quantum communication, yet the security of protocols such as Quantum Key Distribution (QKD) depends critically on the Photon Number Coherence (PNC) of the emitted state. We investigate the generation and control of PNC in GaAs quantum dots under resonant two-photon excitation regimes, comparing standard biexciton-exciton cascading with stimulated two-photon excitation. While standard TPE yields negligible PNC due to incoherent relaxation processes, we demonstrate that the stimulated scheme effectively preserves electronic coherence, enabling on-demand tuning of PNC from zero to maximum values simply by varying the excitation pulse area. This stimulated approach simultaneously enhances photon indistinguishability to 95% while maintaining high purity [1]. Furthermore, addressing the sensitivity of TPE to environmental fluctuations, we introduce a robust stimulated adiabatic rapid passage (sARP) scheme[2]. We show that sARP maintains stable, vanishing PNC even in the presence of power drifts, for tailoring photon statistics to the specific security requirements of advanced quantum network protocols[1, 2].
[1] Karli, Y. et al. npj Quantum Inf. 10, 17. [2] Karli, Y. et al. Appl. Phys. Lett. 125 (25)
Keywords: PNC; coherence; QKD; single photon