UBI seminar
 Date: September 25, 14:00~
 Place: Room 413, Science Building No.1, Hongo Campus, the Univ. of Tokyo
 Speaker:Dr. Amit Kumar Chatterjee (Kyoto University)
 Title: Quantum Mpemba effect: an anomalous relaxation in quantum systems

Mpemba effect refers to the counter-intuitive phenomenon where a hotter object can cool down faster than a colder copy of the same object. In spite of some theoretical as well as experimental advances in the classical domain, the quantum counterpart of the Mpemba effect, specifically in temperature, has remained unexplored. In this talk, we demonstrate the quantum Mpemba effect by showing that temperatures of two copies of a quantum system, one initially hotter than the other, can cross each other after some time and thereafter reverse their identities, i.e. hotter becomes colder and vice versa, before reaching the same final temperature. In fact, we show such crossing of trajectories characterizing the quantum Mpemba effect, can occur in several other observables including energy, entropy, distance function etc. Our theoretical results on quantum Mpemba effect are primarily based on a quantum dot connected to two reservoirs. In the later part of the talk, we discuss how exceptional points and complex eigenvalues can lead to multiple quantum Mpemba effect (where trajectories cross multiple times) in a two-level driven dissipative system. Reference: A. K. Chatterjee, S. Takada, and H. Hayakawa, Phys. Rev. Lett. 131, 080402 (2023).