# Journal Club: Quantum Thermodynamics

## Tamás Kiss

### (Department of Quantum Optics and Quantum Information, Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences)

Time: Tue Jun 18 15:00:00 2013

Location: Building 1, Room 114, Auditorium

#### Tatsuhiko N. Ikeda, Naoyuki Sakumichi, Anatoli Polkovnikov, and Masahito Ueda

*Emergent Second Law in Pure Quantum States*

arXiv:1303.5471

We show that the second law emerges from an isolated pure quantum state through its unitary evolution. The physics behind the second law is the quantum-mechanical energy uncertainty associated with every finite-time operation that makes a large number of many-body energy eigenstates indistinguishable, resulting in a non-decreasing entropy of the system. Our result establishes the quantum-mechanical definition of the thermodynamic entropy, opening up the way to study thermodynamics in isolated quantum systems, where persistent quantum coherence is expected to cause hitherto unexplored effects. In fact, independently of details of the system and processes, quantum coherence between many-body eigenstates is shown to bring about a universal many-body correction to the entropy. Such new effects are expected to be experimentally observed using ultracold atoms or ions.