Probing Temperature by Using Decoherence Dynamics

We suggest open quantum systems out-of-equilibrium as effective quantum probes for the characterisation of their environment. We discuss estimation schemes for parameters driving a dephasing evolution of the probe and then focus on qubits, establishing a relationship between the quantum Fisher information and the residual coherence of the probe. Finally, we address the dephasing dynamics of a qubit as an effective process to estimate the temperature of its environment.