# ENTANGLEMENT COMPLEXITY AND THE EMERGENCE OF IRREVERSIBILITY IN QUANTUM MECHANICS

on the June 29, 2018

At 11:00am

Seminar by Alioscia Hamma of University of Massachusetts, Boston

The onset of irreversibility in physics is one of the great questions at the heart of statistical mechanics. The second principle of thermodynamics in essence states that spontaneous processes happen in one direction. In classical physics irreversibility can only happen with some seed of randomness or coarse graining and topological mixing. Since coarse graining and the counting of micro states is arbitrary in classical physics, firmer grounds for statistical mechanics must be found in the quantum domain. At a first glance the quantum case looks even harder. In a closed system evolution is unitary, and therefore the entropy of a quantum state cannot increase. Moreover, unitary evolution is always reversible, so irreversibility is strictly speaking impossible. In classical mechanics irreversibility is due to chaos, that is, high sensitivity to initial conditions. But in quantum mechanics, unitarity implies that slightly different initial conditions do not evolve into highly different states. In this talk we take seriously the idea that the defining feature of quantum mechanics is entanglement. As such, irreversibility must be a consequence of entanglement. As we shall see, it is not the amount of entanglement per se that is important, but its complexity. We show that complexity of entanglement classifies the dynamical behavior of a isolated quantum many-body system and determines its irreversibility and the approach to thermalization.

For invitation to access the CNRS campus, please contact :anna.minguzzi@grenoble.cnrs.fr

For invitation to access the CNRS campus, please contact :anna.minguzzi@grenoble.cnrs.fr

Published on June 27, 2018

### Practical informations

#### Lieu(x)

Laboratoire de Physique et Modélisation des Milieux Condensés (LPMMC)

Amphithéatre

25 Avenue des Martyrs, 38000 Grenoble