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QI: Fachverband Quanteninformation
QI 18: Poster II
QI 18.35: Poster
Wednesday, March 20, 2024, 11:00–14:30, Poster A
Spin-up tunnelling detection in noisy readout for SiMOS qubit — •Noah Gläser1, Viktor Adam2, Clément Godfrin3, and Wolfgang Wernsdorfer1,2 — 1PHI (KIT), Wolfgang- Gaede-Str. 1, 76131 Karlsruhe — 2IQMT (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen — 3imec, Remisebosweg 1, 3001 Leuven
We present an algorithm for binarisation of noisy binary data in the limit of low signal-to-noise ratio (SNR). The algorithm was initially developed for readout of a SiMOS qubit featuring a Single Electron Transistor (SET) to sense charge in a close-by quantum dot. Each measured SET current stems from one of two distinct levels, representing the absence/presence of a single electron in the quantum dot. The challenge is to revert the current back to the binary signal, in order to decide if level jumps occurred during the measurement. For sufficiently large SNR ( 3), this can be done with a threshold filter, but fails if the standard deviation of the noise exceeds the difference between the two levels. Our algorithm extracts the qubit’s spin-up fraction reliably in three steps, even at SNR 1. First, it automatically identifies the two current levels. In a second step, we adapt total variation denoising to our binary case to obtain the underlying sequence of presence/absence of the electron. A maximum likelihood estimator then utilises the time-resolved signal edges to deduce the obtained spin-up fraction, which is the main quantity of interest for the qubit readout. Finally, we demonstrate the algorithm’s performance compared to the threshold method on experimental data.
Keywords: Quantum Dot; SiMOS; Noise; Single Electron Transistor; Qubit