Nonequilibrium thermometry via an ensemble of initially correlated qubits
Year: 2026
Authors: Trombetti E., Malitesta M., Pezzutto M., Gherardini S.
Autors Affiliation: CNR, INO, Largo Enrico Fermi 6, I-50125 Florence, Italy; Univ Napoli Federico II, Dept Phys Ettore Pancini, I-80126 Naples, Italy; Univ Firenze, Dept Phys & Astron, Via Sansone 1, I-50019 Sesto Fiorentino, Italy; Univ Firenze, European Lab Nonlinear Spect, I-50019 Sesto Fiorentino, Italy.
Abstract: We investigate a nonequilibrium quantum thermometry protocol in which an ensemble of qubits, acting as temperature probes, is weakly coupled to a macroscopic thermal bath. The temperature of the bath, the parameter of interest, is encoded in the dissipator of a Markovian thermalization process. For some relevant initial states, we observe a peak in the Quantum Fisher Information (QFI) during the transient of the thermalization, indicating enhanced sensitivity in early-time dynamics. This effect becomes more pronounced at higher bath temperatures and is further enhanced when the initial reduced state of the qubits has a large ground-state population and/or it is highly coherent. We also focus on the role of initial quantum correlations in the thermometric performance, which emerge as a central feature of this work. We find strong numerical evidence that, given same singlequbit reduced states, the inclusion of quantum correlations among the qubits of the ensemble always yields an enhanced QFI. Moreover, even if none of the considered states outperform the (pure, separable) ground state, maximally entangled states display QFIs values remarkably close to the standard quantum limit when probing extremely hot thermal baths. Finally, although the Markovian dynamics does not permit superlinear scaling of the QFI with the number of probes, we identify the most effective initial states for designing high-precision quantum thermometers within this setting. We also provide concrete guidelines for experimental implementations.
Journal/Review: PHYSICAL REVIEW A
Volume: 113 (6) Pages from: 62208-1 to: 62208-19
More Information: The authors acknowledge very useful discussions with Lorenzo Buffoni, Angelo Carollo, Beatrice Donelli, Goncalo Frazao, Seth Lloyd, Yasir Mehmood, and Andrea Smirne. This work has been financial supported by the PNRR MUR Project No. PE0000023 NQSTI funded by the European Union-Next Generation EU, the PRIN Project No. 2022FEXLYB Quantum Reservoir Computing (QuReCo) , and the European project High Performance Computer and Quantum Simulator hybrid (HPCQS) with Grant Agreement No. 101018180 funded by the European Union’s Horizon 2020 research and innovation programme.KeyWords: Quantum; StatesDOI: 10.1103/bb24-kfrz
