The dynamical convergence to the Gibbs state is a standard assumption across much of classical and quantum thermodynamics. However, for nanoscale and quantum systems the interaction with their environment becomes non-negligible. Then so-called mean force (MF) states are the equilibrium states [2,3]. I will discuss general analytic expressions for such MF states in the limits of weak and ultrastrong system-environment coupling [1]. Deviations from the predictions of standard Gibbs physics are exemplified on the V-system.

In the second part of my talk I will discuss our recent results on a very different aspect:

Experiments often encode qubit states in physical systems that have many more physical dimensions. Unfortunately, environmental noise can cause leakage into these dimensions, compromising the qubit nature of the state. This results in unwanted artefacts, such as increased entropies. I will describe a new method to recover a meaningful qubit state from a known noisy high-dimensional state [4].

[1] Cresser, Anders, PRL 127, 250601 (2021)


[2] Trushechkin, Merkli, Cresser, Anders, AVS Quantum Sci. 4, 012301 (2022)

[3] see also F. Cerisola’s talk and arXiv:2204.10874

[4] Anders, ..., Huard, in preparation.