Regensburg 2025 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 21: Quantum Dots and Wires: Transport (joint session HL/TT)

TT 21.7: Vortrag

Dienstag, 18. März 2025, 12:45–13:00, H13

Revealing Hidden States in Quantum Dot Array Dynamics: Quantum Polyspectra Versus Waiting Time Analysis — •Markus Sifft¹, Johannes C. Bayer², Daniel Hägele¹, and Rolf J. Haug² — ¹Faculty of Physics and Astronomy, Ruhr University Bochum, GER — ²Institute of Solid State Physics, Leibniz Universität Hannover, GER

We show how by virtue of the recently introduced quantum polyspectral analysis of transport measurements [1,2], the complex transport measurements of multi-electron QD systems can be analyzed. This method directly relates higher-order temporal correlations of a raw quantum point contact (QPC) current measurement to the Liouvillian of the measured quantum system. By applying this method to a two-electron double QD system, we uncover dynamics between singlet and triplet states, indistinguishable in the QPC current, without requiring the identification of quantum jumps or prior assumptions about the number of quantum states involved. Our findings demonstrate that system models in such cases of hidden dynamics are inherently non-unique. Furthermore, we compare our method to a traditional analysis via the waiting-time distribution. Our method achieves parameter estimates with up to 50% lower errors, while also being applicable in scenarios with low signal-to-noise, where traditional counting methods falter. Our approach challenges previous assumptions and models, offering a more nuanced understanding of QD dynamics and paving the way for the optimization of quantum devices. [1] Hägele et al., PRB 98, 205143 (2018), [2] Sifft et al., PRR 3, 033123 (2021)

Keywords: Polyspectra; Waiting Time Distribution; Double Quantum Dot; Quantum System Characterization; Hidden Markov Models