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FRI: Friday Contributed Sessions
FRI 5: QIP Implementations: Solid-State Devices II
FRI 5.3: Talk
Friday, September 12, 2025, 11:15–11:30, ZHG006
Two-photon spectrum and dynamics of a quantum dot under phonon-assisted excitation — •Lennart Jehle1, Lena Maria Hansen1, Thomas Sando1, Patrik Isene Sund1, Raphael Joos2, Simone Luca Portalupi2, Mathieu Bozzio1, Peter Michler2, and Philip Walther1 — 1University of Vienna, Faculty of Physics, Vienna Center for Quantum Science and Technology (VCQ), 1090 Vienna, Austria — 2Institut für Halbleiteroptik und Funktionelle Grenzflächen, University of Stuttgart, 70569 Stuttgart, Germany
Quantum dots promise to emit with high probability exactly one photon when pumped by a short laser pulse. However, there exists a finite chance of exciting the quantum dot twice within the duration of a single laser pulse, leading to the consecutive emission of two photons and imposing a fundamental limit on the multiphoton probability. Here, we resolve the distinct temporal shape of each of the photons' wavepackets using fast coincidence detection and report an asymmetric two-photon spectrum unique to phonon-assisted excitation. We demonstrate how this two-photon process provides insights into the emission dynamics and enables a direct measurement of the effective Rabi frequency, thus allowing us for the first time to extract the Rabi frequency of a non-resonantly driven quantum dot. By extending the temporal and spectral analysis further, we uncover correlations between the emission time and wavelength. Finally, we use this new understanding of the re-excitation process to maintain a low multiphoton probability regardless of the laser pulse length and thus improve the performance for quantum cryptography and quantum computing.
Keywords: quantum dots; two-photon emission; quantum cryptography; rabi frequency; stark shift