Academic Year 2026

• Thermodynamic Signatures of Coherent Initial Ensembles
  • Pranay Nayak (Stockholm University)
    
  • 2026/04/27 16:00 --
    
  • Seminar Room K202, Main Building, Yukawa Institute, Kyoto U.
    
  • Bit-Erasure involves sampling an initial state from an ensemble of states and resetting it to a reference state of choice. Very different from classical bit-erasure of two possible initial states, we have inumberable possibilities of initial states in quantum bit-erasure due to quantum superposition of states. Here we isolate and investigate the thermodynamic signatures of these coherent superpositions in the initial ensemble of states. We specifically look into moments of work and derive some analytical results that we illustrate with the example of quantum bit erasure. On the way, we will see coherence acting as a resource for precision, and an interesting quantum bound on classical work.
    
• Microscopic theory of Mpemba effects: Rigorous and universal approaches in classical stochastic systems
  • Naruo Ohga (Kyoto University)
    
  • 2026/04/22 16:00 --
    
  • Seminar Room K202, Main Building, Yukawa Institute, Kyoto U.
    
  • The Mpemba effect (MPE), in which a hotter system cools faster than a colder one, has attracted attention as an anomalous relaxation process observed across various mesoscopic and macroscopic systems. However, the connection between MPEs and the microscopic properties of systems has mostly been analyzed on a case-by-case basis. In this seminar, I will present two universal results that enhance the microscopic understanding and analysis of MPEs (N. Ohga, H. Hayakawa, & S. Ito, arXiv:2410.06623). Firstly, I propose a universal microscopic origin of MPEs, dubbed the " microstate MPE." The microstate MPE is interpreted as metastability of one microstate relative to another. Thus, it provides the precise definition of metastability required for MPEs, different from the metastability of potential functions considered in the literature. Secondly, I present a "no-Mpemba theorem" that proves the absence of MPEs based on microscopic descriptions of some classes of spin and particle systems. Combined with previous findings on the existence of MPEs, this theorem elucidates the "boundary" between systems with and without MPEs.
    
• Information-thermodynamic bounds on precision in interacting quantum systems
  • Ryotaro Honma (YITP, Kyoto University)
    
  • 2026/04/15 16:00 --
    
  • Seminar Room K202, Main Building, Yukawa Institute, Kyoto U.
    
  • The thermodynamic uncertainty relation quantifies a trade-off between the relative fluctuations of trajectory currents and the thermodynamic cost, indicating that current precision is fundamentally constrained by entropy production. In classical bipartite systems, it has been shown that information flow between subsystems can enhance current precision in addition to thermodynamic dissipation. In this study, we investigate how information flow, local dissipation, and quantum effects jointly constrain current fluctuations within a subsystem of interacting quantum systems. We further clarify how quantum effects contribute to the bound through a correction term. Unlike in classical bipartite systems, we show that this correction term does not vanish even in the fast- relaxation limit. These results have important implications for the performance of quantum thermal machines, such as information- thermodynamic engines and quantum clocks. We validate our theoretical findings through numerical simulations of a representative quantum clock model. Additionally, we consider situations in which multiple currents are observed and derive an improved bound by optimizing over these currents. Our results extend thermodynamic uncertainty relations to multipartite open quantum systems and elucidate the functional role of information flow in fluctuation suppression. reference: Ref: R. Honma and T. Van Vu, Phys. Rev. A 113, 032207 (2026)