QLunch: Alvaro Alhambra

Speaker: Alvaro Alhambra, CSIC, Spain

Title: Modelling quantum thermalization in nature and with quantum computers

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 that thermal equilibrium 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 algoriths, (KMS detailed balance) circumvents it. Based on that notion, we derive from a microscopic description a master equation that describes thermalization. This provides a rigorous model of many-body thermalization relevant to both open quantum systems and quantum algorithms.