Bonn 2025 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 27: Poster – Ultra-cold Atoms, Ions and BEC (joint session A/Q)

Q 27.10: Poster

Tuesday, March 11, 2025, 14:00–16:00, Tent

Bayesian Thermometry with Single-Atom Quantum Probes for Ultracold Gases — •Julian Feß, Sabrina Burgardt, Silvia Hiebel, and Artur Widera — Department of Physics, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany

Quantum probes are atomic sized devices mapping information of their environment to quantum mechanical states. By improving measurements and at the same time minimizing perturbation of the environment, they form a central asset for quantum technologies. We experimentally realize spin-based quantum thermometers by immersing individual Cs atoms into an ultracold Rb bath. Controlling inelastic spin-exchange processes between the probe and bath allows us to map motional and thermal information onto quantum-spin states. We find that the information gain per inelastic collision can be maximized by harnessing the nonequilibrium spin dynamics. The parameters that need to be tuned to achieve maximum information gain depend on the temperature being estimated, making this system well-suited for Bayesian estimation strategies. In this work, we compare three protocols: unoptimized, a priori optimized, and adaptively optimized. These protocols are evaluated based on their convergence speed and the magnitude of the estimation error. Among them, the adaptive protocol performs best, as it dynamically adjusts the parameters to optimize the information gained from each measurement. This approach highlights the potential of leveraging nonequilibrium dynamics to optimize measurement strategies, paving the way for more efficient and precise quantum thermometry.

Keywords: Bayesian Thermometry; Single Atoms; Open Quantum Systems; Optimal Probing