Skip to content Skip to navigation

Viewpoint: Surfing on a Wave of Quantum Chaos

X. Qi; adapted by APS/Alan Stonebraker
Sep 16 2019
Categories: 
Faculty

Viewpoint: Surfing on a Wave of Quantum Chaos

Written by Professor Xiaoliang Qi.  Article appears in Physics, a free online magazine from the American Physical Society.
 
A model based on Brownian motion describes the tsunami-like propagation of chaotic behavior in a system of quantum particles.
 
In daily life, “chaos” describes anything messy. In physics, the term has a more specific meaning: It refers to systems that, while subject to deterministic laws, are totally unpredictable because of an exponential sensitivity to initial conditions—think of the butterfly flapping its wings and causing a distant tornado. But how does the chaos observed in the classical, macroscopic world emerge from the quantum-mechanical laws that govern the microscopic world? A recently proposed explanation invokes quantum “information scrambling”, in which information gets rapidly dispersed into quantum correlations among the particles of a system. This scrambling is a memory-loss mechanism that can cause the unpredictability of chaos. Developing a theory that fully describes information scrambling remains, however, a daunting task. Now, Shenglong Xu and Brian Swingle of the University of Maryland, College Park, have taken a step toward this description by studying chaos with models based on a quantum version of Brownian motion. Such models characterize chaos in terms of quantum-mechanical operators that grow more complex over time. Xu and Swingle show that this formalism enables a quantitative description of how chaos spreads in a many-body system. [Read more.]