Non-Abelian Berry Phase

A degenerate quantum system transported adiabatically around loops in parameter space acquires a non-commuting (matrix) holonomy. Two loops in different orders give different final states — the heart of topological quantum gates.

Loop Parameters

Holonomy Matrices

Computing...

Non-commutativity

|U₁U₂ - U₂U₁|: -
Order: U₁ then U₂
Phase: Loop 1