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Regensburg 2022 – wissenschaftliches Programm

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QI: Fachverband Quanteninformation

QI 2: Quantum Thermodynamics and Open Quantum Systems

QI 2.8: Vortrag

Montag, 5. September 2022, 12:00–12:15, H9

Large fluctuations of qubit decoherence under 1/f noise of a sparse bath of two-level fluctuators — •Mohammad Mehmandoost and Viatcheslav Dobrovitski — QuTech and Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands

We theoretically study the qubit decoherence caused by 1/f noise of a sparse bath of Two-Level Fluctuators (TLFs) in the Ramsey and Hahn echo experiments. We focus on the role of bath density d, defined as the ratio of the number of TLFs n to the logarithmic frequency range ln(γMm), on the qubit decoherence. The first spectral density of 1/f noise produced by sparse bath samples, small d, are roughly similar. The qubit decoherence in this regime is, however, not fully characterized by the noise first spectral density. We therefore use the exact expressions describing the qubit decoherence coupled to a sample TLF bath. Using Monte Carlo simulations, we show that the qubit decoherence is subject to large sample-to-sample fluctuations in sparse baths of fixed density d. This highlights the necessity to adopt a statistical approach to characterize the qubit decoherence in this regime. We also found that the qubit decoherence under 1/f noise of sparse TLF baths is governed by only a few TLFs. We show that if these TLFs are removed, the coherence times are substantially improved. We hope the latter finding opens up a way to improve the coherence times of the state-of-the-art qubits affected by 1/f noise.

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