Freiburg 2024 – scientific programme

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SYQO: Symposium Ultrafast Quantum Nano-Optics

SYQO 1: Ultrafast Quantum Nano-Optics

SYQO 1.5: Talk

Friday, March 15, 2024, 12:45–13:00, Paulussaal

Observing Ultrafast Coherent Dynamics following Selective Excitation of a Single Quantum Dot — •Darius Hashemi Kalibar, Philipp Henzler, Ron Tenne, and Alfred Leitenstorfer — Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany

Precise observation and control of coherent state evolution are a prerequisite for the application of quantum technologies. However, in many systems, the bandwidth of quantum effects is limited by their relatively slow response times. In contrast, using ultrashort optical pulses to control quantum-confined electrons allows for quantum experiments on the much faster femtosecond timescale. In this work, we describe an all-optical approach for the ultrafast selective initialization of excitonic states in individual CdSe/ZnSe quantum dots at cryogenic temperatures and observe their evolution through pump-probe spectroscopy. Resonantly-tuned 500 fs pump pulses excite the quantum dot from the ground state into trion triplet states. Subsequently, 150 fs probe pulses spanning multiple transitions enable direct time-resolved observation of the quantum dynamics. We observe persistent spin quantum beats between two excitonic states despite femtosecond orbital relaxation of the hole. Control of the polarization of the pump pulses enables selective excitation of a single state, avoiding the beating phenomenon. Together, these advances form a major step towards quantum sensing on ultrafast time and nanometric spatial scales.

Keywords: Quantum dots; Coherent control; Coherent exciton dynamics; Ultrafast spectroscopy; Pump-probe microscopy