Steve Campbell

University College Dublin & Freie Universität Berlin

Thermometry of many-body quantum systems with impurity probes

Using quantum systems as probes for parameter estimation offers a remarkably versatile playground. Ensuring that the optimal precision is achievable depends on a variety of factors: the structure of the probe, the nature of the sensing protocol, and the microscopic details of the sample, are a few of the key ingredients. In this talk I will focus on thermometry, discussing the features that a good quantum (equilibrium) probe must have to achieve optimal sensitivity. We extend this to considering how thermometric sensitivity is impacted when the sample is an interacting, possibly critical, many-body system. The delicacy of critical systems to perturbations can make them ideal sensors but this comes with some caveats, including severely limiting the parameter range that the probe is sensitive to. Finally, I will briefly discuss subtleties that arise when extending to multi-parameter estimation settings.

This presentation will draw on results from a number of recent(ish) papers including:
• Precision thermometry and the quantum speed limit, Steve Campbell, Marco G. Genoni, and Sebastian Deffner, Quantum Sci. Technol. 3, 025002 (2018).
• Thermometry of strongly correlated fermionic quantum systems using impurity probes, George Mihailescu, Steve Campbell, and Andrew K. Mitchell, Phys. Rev. A 107, 042614 (2023).
• Multiparameter critical quantum metrology with impurity probes, George Mihailescu, Abolfazl Bayat, Steve Campbell, and Andrew K. Mitchell, Quantum Sci. Technol. 9, 035033 (2024).