Quantum Thermodynamics

Quantum Thermodynamics is a relatively young research field that tries to extend classical thermodynamics concepts all the way to the quantum regime. The reasons for doing so are manifold, ranging from answering to fundamental questions to more applied goals.

Entropy Production in Continuously Measured Quantum Systems

The entropy production rate is a key quantity in non-equilibrium thermodynamics of both classical and quantum processes. No universal theory of entropy production is available to date, which hinders progress towards its full grasping. By using a powerful phase space-based approach, in this work [Belenchia et al., arXiv:1908.09382, https://www.nature.com/articles/s41534-020-00334-6] we extend the current framework for the assessment of thermodynamic irreversibility by characterizing entropy production resulting from the continuous monitoring of a Gaussian system. This allows us to formulate a sharpened second law of thermodynamics that accounts for the measurement back-action and information gain from a continuously monitored system.

Experimental assessment of entropy production in a continuously measured mechanical resonator

In collaboration with the experimental group lead by Prof. Albert Schliesser in Copenhagen, in [Rossi et al., arXiv:2005.03429 ] we report on the experimental inference of the stochastic entropy production rate for a continuously monitored mesoscopic quantum system. We consider an optomechanical system subjected to continuous displacement Gaussian measurements and characterise the entropy production rate of the individual trajectories followed by the system in its stochastic dynamics. Owing to the specific regime of our experiment, we are able to single out the informational contribution to the entropy production arising from conditioning the state on the measurement outcomes. 

The role of quantum coherence in energy fluctuations

In this work, we investigate the role of quantum coherence in energy fluctuations of an open quantum system and we advance an alternative to the two-point measurement scheme which involves only one final measurement. This operational protocol, which we refer to as the end-point-measurement scheme, allows defining the statistics of energy changes as a function of energy measurements performed only after the system evolution.

In a new version of the same work, that you can find here, we also test our theoretical framework employing the IBM Quantum and performing some experiments with their qubits.

Informational steady-states and conditional entropy production in continuously monitored systems

Here we put forth an overarching framework for constructing a theory of conditional thermodynamics beyond the Gaussian approximation. In particular, our framework introduces the notion of information steady states – a steady states of matter that only exist because measurements are being continually performed – and extend our previous works quantifying the entropy production in monitored Gaussian systems.