IQIM Postdoctoral and Graduate Student Seminar

Friday November 13, 2020 11:00 AM

Hierarchy of light cones in power-law interacting systems: review of recent bounds and saturating protocols

Speaker: Chi-Fang (Anthony) Chen
Location: Online Event

Abstract: In quantum many-body systems with local interactions, quantum information and entanglement cannot spread outside of a linear light cone, which expands at an emergent velocity analogous to the speed of light. Though, realistic systems often have a power-law interaction 1/r^α. In this talk, we discuss a hierarchy of light cones in these long-ranged systems: At the same α, some quantum information processing tasks are constrained by a `linear' light cone, while others are not. In one spatial dimension, a linear light cone exists for every many-body state when α > 3 (Lieb-Robinson light cone); for a typical state chosen uniformly at random when α > 5/2 (Frobenius light cone); and for every state of a noninteracting system when α > 2 (free light cone). These bounds apply to time-dependent systems and are saturated by explicit protocols. Some of these linear light cones extend to algebraic ones and/or generalize to higher dimensions. As an example among the various implications, universal quantum state transfer, as well as many-body quantum chaos, is bounded by the Frobenius light cone and, therefore, is poorly constrained by all Lieb-Robinson bounds. This talk will be an up-to-date review over regimes of α, recent protocols and the key physical intuitions and the high-level proof ideas.
Arxiv: (main theme)

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Series IQIM Postdoctoral and Graduate Student Seminar Series

Contact: Marcia Brown at 626-395-4013