##### Department of Mathematics,

University of California San Diego

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### Math 243, Functional Analysis

## Dr. Junhwi Lim

#### Vanderbilt University

## An index for quantum cellular automata on fusion spin chains

##### Abstract:

The index for 1D quantum cellular automata (QCA) was introduced to measure the flow of the information by Gross, Nesme, Vogts, and Werner. Interpreting the index as the ratio of the Jones index for subfactors leads to a generalization of the index defined for QCA on more general abstract spin chains. These include fusion spin chains, which arise as the local operators invariant under a global (categorical/MPO) symmetry, and as the boundary operators on 2D topologically ordered spin systems. We introduce our generalization of index and show that it is a complete invariant for the group of QCA modulo finite depth circuits for the fusion spin chains built from the fusion category Fib. This talk is based on a joint work with Corey Jones.

Host: Priyanga Ganesan

### January 23, 2024

### 11:00 AM

Zoom (meeting ID: 94246284235)

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