  The interference pattern produced by a quantum particle in Young's
double-slit setup is attributed to the particle's wavefunction having gone
through both slits. In the path integral formulation, this interference
involves a superposition of paths, going through either slit, linking the
source to the detection point. We show how these paths superpositions can in
principle be observed by implementing a series of minimally-perturbing weak
measurements between the slits and the detection plane. We further propose a
simplified protocol in order to observe these "weak trajectories" with single
photons.

Quantum Physics