Operational approach to the Uhlmann holonomy
  We suggest a physical interpretation of the Uhlmann amplitude of a density operator. Given this interpretation we propose an operational approach to obtain the Uhlmann condition for parallelity. This allows us to realize parallel transport along a sequence of density operators by an iterative preparation procedure. At the final step the resulting Uhlmann holonomy can be determined via interferometric measurements. 
Johan Aberg, David Kult, Erik Sj\"oqvist, and D.K.L. Oi