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Résumé |
In this seminar, I will introduce the entanglement asymmetry, a quantum information based observable that
measures how much a symmetry is broken in a part of an extended quantum system. I will then discuss two
applications of it. First, I consider a spin chain in which a symmetry explicitly broken by the initial state is
dynamically restored by the time evolution after a quantum quench. Unexpectedly, the more the symmetry is
initially broken, the faster is restored, a quantum version of the counterintuitive and yet mysterious Mpemba
effect. As a second application, I will use the entanglement asymmetry to monitor the broken symmetries of a
black hole during its evaporation. I will show that, if the black hole initially breaks an arbitrary U(1) symmetry,
the emitted radiation is in a symmetric state until the halfway point of the evaporation, the Page time, at
which undergoes a sharp transition to a state that breaks the symmetry. |
