CM Seminar: "Quantum many-body physics: from quantum thermalization to measurement-induced phenomena." (Pablo Sala, CalTech)

  • Starts: 3:30 pm on Wednesday, November 29, 2023
  • Ends: 4:30 pm on Wednesday, November 29, 2023
This seminar is divided in two parts. In the first half, we explore the dynamics of quantum many-body systems when certain unconventional quantities are conserved. We will show that the conservation of a charge and its associated dipole moment leads to a provable fragmentation of the Hilbert space into exponentially many disconnected sectors. In turn, this leads to novel universal hydrodynamic behavior, and can translate into non-vanishing bulk correlators and the existence of localized boundary modes akin strong zero modes, among other unexpected phenomena both in and out of equilibrium. We then show that dipole-conserving models become good approximations of strongly-tilted interacting systems, and discuss ultra-cold atoms experiments in this regime. So far measurements only appeared as a mean to probe the system of interest. Nonetheless, they can also be a useful resource to realize novel quantum phenomena. In this second half of the talk, we study the impact of measurements on the paradigmatic Ising quantum critical chain. We show that measurements can qualitatively alter long-distance correlations in a manner dependent on the measurement protocol and the nature of ancilla correlations. Measurements can, for example, modify the Ising order parameter scaling dimension and catalyze order parameter condensation. We derive numerous quantitative predictions for the behavior of correlations in select measurement outcomes, and also identify two strategies for detecting measurement-altered Ising criticality in measurement-averaged quantities. Our framework naturally adapts to more exotic quantum critical points and highlights opportunities for potential experimental realization in Rydberg arrays.
SCI 352
Pablo Sala
Alexey Khudorozhkov