Figure 1: The Mach–Zehnder interferometer.
From: The uncertainty principle enables non-classical dynamics in an interferometer
Branch locality, the restriction whose consequences the uncertainty principle enables escape from, states that if the (possibly post-quantum) particle is with probability 1 to be found in one of the branches of the interferometer (for example, up), then operations on the other spatially disjoint branch (for example, low) cannot change the operational state of the particle.
