# Macroscopic Quantumness in many-body systems

- Speaker: Chae-Yeun Park (Seoul National Univ)
- Date: Thursday November 19, 2015 17:00
- Place: Jeongho Seminar Room

Quantum information theory opened a new perspective in quantum many-body physics. Entanglement has mainly been used to investigate many interesting phenomena in many-body physics. However, entanglement solely cannot reveal all different quantum properties of the states. Quantum superposition between macroscopic different states which is well illustrated in Schrödinger's cat paradox is one of such properties. In this talk, we first show that how the size of macroscopic quantum superposition can be measured and how this measure can be used to investigate the interesting physics in a many-body system. Using disordered quantum Heisenberg chain which alters between thermalization phase and many-body localization phase depending on the disorder strength, it is shown that a macroscopic quantum superposition disappears even in a closed system which can be understood using eigenstate thermalization hypothesis.