2 July 2020 Thu 11 am

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Observational entropy is a framework of assigning an entropy to a system based on a coarse-graining. The concept itself is a generalization of Boltzmann entropy (of general coarse-graining) to quantum systems, and dates back all the way to von Neumann. It can be applied to both classical and fully quantum systems, and takes into account quantum features such as non-commutativity and superposition. It connects many different notions of entropy, and reduces to several known ones when appropriate coarse-graining is considered. One of the application is a notion of non-equilibrium thermodynamic entropy, which is additive, increases when the system is out-of-equilibrium, and corresponds to equilibrium entropy when the system is in equilibrium. The aim of this talk is to introduce this framework reasonably pedagogically, and to give the audience the intuition behind of what is this framework is about and what it is capable of.