Abstract: Quantum systems are typically coupled to an external environment, with which they equilibrate to a specific temperature. However, the usual master equations modelling the equilibration towards thermal distributions do not apply to generic many-body systems, with small level spacings. We explain how this issue stems from an inadequate quantum generalization of detailed balance, and show that a notion recently considered in quantum algorithms (KMS detailed balance) circumvents it. Additionally, we show how this notion appears to be key in how we model system-bath thermalization from first principles under weak coupling, and how it allows us to rigorously analyze near-term quantum algorithms for Gibbs sampling based on single-qubit collisions, for which experimental progress is already underway. For all these models we also outline existing results on rigorous convergence guarantee.

About the speaker: Dr. Álvaro Alhambra is a staff scientist at the Institute for Theoretical Physics-CSIC in Madrid (Spain). He obtained his PhD in 2017 at University College London, and was later a postdoctoral researcher at Perimeter Institute in Canada, and the Max Planck Institute for Quantum Optics in Germany, where he was a Humboldt fellow.

His research is at the interface of statistical and many-body physics with quantum information and computation, with a mathematical perspective. He has worked on non-equilibrium and thermodynamics of quantum systems, and on their complexity and simulatability through both classical and quantum algorithms.

Inviter: 孙孝奇 xqsun@iphy.ac.cn