Berlin 2024 – scientific programme

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QI: Fachverband Quanteninformation

QI 32: Quantum Sensing and Metrology

QI 32.7: Talk

Friday, March 22, 2024, 11:30–11:45, HFT-FT 131

Magnetometry with Driven Spin Systems — •Dhruv Deshmukh and Joachim Ankerhold — Institute for complex quantum systems, Ulm University, Germany

The dynamics of time-dependent two-level system is a well addressed problem in quantum physics that has spurred the development of many novel techniques and technologies due to its widespread applicability. Here, we focus on the problem of a two-level system driven linearly over the entire parameter space of amplitude and frequency of the classical drive. This problem does not have analytical solutions and has only been solved approximately, near resonance for a weak drive and, for high-frequency drives. Employing Floquet formalism, we have found special manifolds on the parameter space for which the entire Bloch Sphere exhibits period multiplicity. This treatment allows for a deeper understanding of the approximate solutions obtained before.

Understanding the Floquet dynamics has proved to be vital for applications in magnetometry. We found that setting drive parameters at the quasi-energy crossing manifolds in the parameter space, yields the highest quantum fisher information (QFI) for magnetic field oriented parallel to the drive. The Floquet dynamics of periodically driven multi-spin clusters, and spin-chains, were also investigated. In regard to magnetometry, we found (for some simple cases) that the QFI scales linearly with the number of spins (Heisenberg scaling) for suitable parameter choices.

Keywords: Magnetometry; Driven Spin Systems; Floquet Physics