Whether the properties of a quantum particle can be ascertained between state preparation and measurement has been much debated. A time-symmetric approach towards quantum mechanics motivates the concept of weak values which can, in some limiting sense, tell us about the property of the particle. The signatures of these properties can be realized with weak measurements.

Using weak measurements and quantum theory, it was suggested that we could obtain signatures of properties of a particle in a path that the particle did not take. Here, we present an experimental realization of simultaneous weak measurements of "which-path" and "polarization component in a given path" observables of single photons in a two-path interferometer. We obtain signatures of one of the polarization components in the arm of the interferometer that the photons do not take when subjected to post-selection.

Further, we briefly discuss the use of weak measurements in computing expectation values of non-Hermitian operators and the role of boundary conditions in interference experiments.