Theory Seminar: Characterization and detection of subsystem symmetry-protected topological order

David Stephen (MPQ Theory Department)
Subsystem symmetry-protected topological (SSPT) order is a new kind of quantum phase of matter that is protected by subsystem symmetries.

February 20, 2019

David Stephen (MPQ Theory Department)
Herbert-Walther Lecture Hall G0.25
Wed 20. February 2019, 11:30 am (MEZ)

Abstract:

Subsystem symmetry-protected topological (SSPT) order is a new kind of quantum phase of matter that is protected by subsystem symmetries. These are symmetries that lie halfway in between global and local (gauge) symmetries, and act on lower-dimensional subsystems of the entire system, e.g. lines, planes, or even fractals. SSPT phases of matter have recently garnered interest due to their close relation to fracton topological order and also to universal measurement-based quantum computation. In this talk, I will first show how SSPT phases of matter can be characterized using tensor networks and quantum cellular automata, and also how this relates to quantum computation. In the second half of the talk, I will show that SSPT phases of matter are associated with corrections to the entanglement area law, similar to the topological entanglement entropy. These corrections are generically uniform throughout a given SSPT phase, and they may therefore be used to detect SSPT order in ground-state wave functions. To test, we use this correction to probe various SSPT phase transitions numerically, with some surprising results.

 

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