# Séminaire du LPTMS : Adam Nahum (LPENS)

## Quantum dynamics with an observer: the measurement phase transition

### Adam Nahum (Laboratoire de Physique de l’Ecole Normale Supérieure)

Onsite seminar + zoom.

Zoom link:

https://cnrs.zoom.us/j/92283605429?pwd=ZTRuWmR4T0dHVWh2M0VRUzhrc2p6QT09

Meeting ID: 922 8360 5429

Passcode: vv58du

In the quantum world, measurements inevitably affect the state of a system, via wavefunction collapse. This means that the dynamics of a system which is continually being monitored by an observer is fundamentally different from the dynamics of a closed system. In particular, for a spatially extended system, local measurements of the degrees of freedom can “compete” with chaotic dynamics: while chaotic dynamics tends to produce complex, entangled quantum wavefunctions, local measurements tend to collapse the wavefunction into something simpler. I will describe how this leads to a dynamical phase transition between a weak monitoring phase, where the state is complex and entangled, and a strong monitoring phase, where the state is simple and “classical”. I will sketch the relevance of this transition to the classical simulation of quantum dynamics, and some theoretical approaches to understanding the transition.

**Date/Time : ** 15/02/2022 - *11:00 - 12:00*

**Location : ** Petit amphi, bâtiment Pascal n° 530

#### Upcoming seminars

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- Soutenance de thèse : Lorenzo Gotta (LPTMS) - 8 Nov 2022 - 00:00
- Physics-Biology interface seminar: Léa Chazot-Franguiadakis - 18 Nov 2022 - 11:00