【Date and Time】7-May-2025 10:30am (Beijing time)

【Venue】Room 526

【Host】Li You (Tsinghua University & BAQIS)

【Title】Beyond-Hermitian Quantum Physics

【Speaker】 

Professor Masahito Ueda is a distinguished physicist at the department of Physics of the University of Tokyo. He earned his Ph.D. in 1991 from the University of Tokyo. Since 2008, he has been serving as a professor at the University of Tokyo. Professor Ueda has made significant contributions to the field of quantum squeezing, particularly in the development and understanding of squeezed spin states. In addition to his role at the University of Tokyo, Professor Ueda leads the Quantum Condensate Research Team at RIKEN's Center for Emergent Matter Science. His team focuses on exploring the frontiers of physics at the intersection of quantum physics, quantum measurement, information, thermodynamics, and machine learning, particularly through the study of nonequilibrium open quantum systems using ultracold atoms.

Throughout his career, Professor Ueda has received numerous accolades, including the Matsuo Prize in 2002, the Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology in 2007, the Nishina Memorial Prize in 2008, and the Japan Society for the Promotion of Science (JSPS) Prize in 2009.

【Abstract】

Isolated quantum systems are described by Hermitian Hamiltonians. However, when they are open to surrounding environments or subject to quantum measurements, one should go beyond the Hermitian framework. Beyond-Hermitian physics has recently attracted a great deal of attention due to remarkable advances in experimental techniques and theoretical methods in AMO, condensed matter and nonequilibrium statistical physics. Complete knowledge about quantum jumps allows a description of quantum dynamics at the single-trajectory level. A subclass thereof without quantum jumps can be described by a non-Hermitian Hamiltonian. Here, symmetry, topology and many-body effects are fundamentally altered from Hermitian physics. In this talk, I will discuss what new potentials can be liberated once we go beyond the Hermitian framework. I will illustrate them in the context of the quantum speed limit, intermediate-state engineering, continuous quantum phase transitions and non-Hermitian topological phases. I will also discuss applications of beyond-Hermitian quantum physics to statistical physics and condensed matter physics, such as Yang-Lee zeros, nonunitary critical phenomena and non-Hermitian BCS superconductivity.