Resonant and Anti-resonant Exciton-Phonon Coupling in Quantum Dot Molecules

Michelle Lienhart; Krzysztof Gawarecki; Markus Stöcker; Frederik Bopp; Charlotte Cullip; Nadeem Akhlaq; Christopher Thalacker; Johannes Schall; Sven Rodt; Arne Ludwig; Dirk Reuter; Stephan Reitzenstein; Kai Müller; Paweł Machnikowski; Jonathan J. Finley

arXiv · 2505.09906

Resonant and Anti-resonant Exciton-Phonon Coupling in Quantum Dot Molecules

Michelle Lienhart·Krzysztof Gawarecki·Markus Stöcker·Frederik Bopp·Charlotte Cullip·Nadeem Akhlaq·Christopher Thalacker·Johannes Schall·Sven Rodt·Arne Ludwig·Dirk Reuter·Stephan Reitzenstein·Kai Müller·Paweł Machnikowski·Jonathan J. Finley

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Abstract

Optically active quantum dot molecules (QDMs) can host multi-spin quantum states with the potential for the deterministic generation of photonic graph states with tailored entanglement structures. Their usefulness for the generation of such non-classical states of light is determined by orbital and spin decoherence mechanisms, particularly phonon-mediated processes dominant at energy scales up to a few millielectronvolts. Here, we directly measure the spectral function of orbital phonon relaxation in a QDM and benchmark our findings against microscopic kp theory. Our results reveal phonon-mediated relaxation rates exhibiting pronounced resonances and anti-resonances, with rates ranging from several ten ns$^{-1}$ to tens of $\mu$s$^{-1}$. Comparison with a kinetic model reveals the voltage (energy) dependent phonon coupling strength and fully explains the interplay between phonon-assisted relaxation and radiative recombination. These anti-resonances can be leveraged to increase the lifetime of energetically unfavorable charge configurations needed for realizing efficient spin-photon interfaces and multi-dimensional cluster states.

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Michelle Lienhart, Krzysztof Gawarecki, Markus Stöcker, Frederik Bopp, Charlotte Cullip, Nadeem Akhlaq, Christopher Thalacker, Johannes Schall, Sven Rodt, Arne Ludwig, Dirk Reuter, Stephan Reitzenstein, Kai Müller, Paweł Machnikowski, Jonathan J. Finley. 2025-05-15. Resonant and Anti-resonant Exciton-Phonon Coupling in Quantum Dot Molecules. https://arxiv.org/abs/2505.09906

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