Francesco Albarelli

Abstract Continuous-variable Gaussian states are ubiquitous in quantum science, describing relevant regimes in optics, optomechanics, and atomic ensembles. In multiparameter quantum metrology, their ultimate precision limit is set by the Holevo Cramér-Rao bound (HCRB), which accounts for measurement incompatibility. However, evaluating the HCRB in infinite-dimensional systems is challenging due to the required optimization over Hermitian operators.

Quantum technologies promise breakthroughs in how we sense, measure, and interact with the world. At the heart of this revolution lies quantum metrology: the science of making ultraprecise measurements using the unique features of quantum systems, such as entanglement and superposition. But in realistic settings, quantum systems are noisy, and their precision is often limited by the practical constraints of time and energy.

One of the main advantages expected from using quantum probes as thermometers is noninvasiveness, i.e., a negligible perturbation to the thermal sample. However, invasiveness is rarely investigated explicitly. Here, focusing on a spin probe undergoing pure dephasing due to the interaction with a bosonic sample, we show that there is a nontrivial relation between the information on the temperature gained by a quantum probe and the heat absorbed by the sample due to the interaction.