Energy-Degenerate Photon-Pair Generation from Individual CsPbBr3 Quantum Dots

Chenglian Zhu^a^,^b, Leon G. Feld^a^,^b, Simon C. Boehme^a^,^b, Ihor Cherniukh^a^,^b, Maryna I. Bodnarchukk^a^,^b, Maksym V. Kovalenko^a^,^b, Gabriele Rainò^a^,^b

^aETH Zurich, Laboratory of Inorganic Chemistry, Department of Chemistry & Applied Biosciences, Vladimir-Prelog-Weg, 1, Zürich, CH

^bLaboratory for Thin Films and Photovoltaics Empa-Swiss Federal Laboratories for Materials Science and Technology Dübendorf CH-8600, Switzerland

Proceedings of Emerging Light Emitting Materials 2025 (EMLEM25)

La Canea, Greece, 2025 October 8th - 10th

Organizers: Maksym Kovalenko and Grigorios Itskos

Oral, Simon C. Boehme, presentation 032
Publication date: 17th July 2025

While single-photon emission continues to drive a broad range of photonic quantum technology, an important next goal in quantum-light generation is the preparation of correlated N-photon bundles, e.g., photon pairs. These higher-order quantum-light resources may act as enabling ingredients for various quantum technologies, including quantum teleportation¹ and quantum metrology.² A prototypical approach to generating entangled photon pairs has been the exploitation of the radiative biexciton cascade (├ |XX⟩ to ├ |X⟩ to ├ |0⟩) in individual epitaxially grown semiconductor quantum dots (QDs)^{3, 4}. In an effort to search for scalable and solution-processable alternative photon-pair sources, we here investigate and engineer the radiative biexciton cascade in individual colloidal CsPbBr₃ QDs. By matching their size-dependent biexciton binding energies^5-9 to their size-independent phonon energies,^{8, 10, 11} we demonstrate the generation of temporally correlated and energy-degenerate photon pairs in large (> 15 nm) CsPbBr₃ QDs. Under pulsed excitation and at cryogenic temperature, we observe a pronounced photon bunching, with g⁽²⁾(0) up to 7 in Hanbury Brown and Twiss measurements. The excitation-dependent bunching is quantitatively reproduced by multi-color numerical calculations,¹² revealing the cooperative biexciton and phonon-mediated exciton emission as the origin of the pronounced bunching. Our findings provide new insights into the energy-degenerate photon-pair generation in this scalable and highly engineerable quantum-light emitting platform, marking an important step towards their application in quantum-information technologies.

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Acknowledgements:

The project was supported by the Swiss National Science Foundation (Grant No. 200021_192308, "Q-Light-Engineered Quantum Light Sources with Nanocrystal Assemblies"), by the Weizmann-ETH Zürich Bridge Program (MORE), by the Air Force Office of Scientific Research under award number FA8655-21-1 7013, and by the European Research Council (grant agreement No. 819740, SCALE-HALO).

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