Quantum Interference of Distinguishable Photons Based on Spatially-Resolved Measurements

We present experimental results demonstrating the quantum interference of two photons distinguishable in their transverse momenta, each entering the input ports of a balanced beam splitter. This counterintuitive interference effect is made possible through spatially resolved measurements in the near field, i.e., by resolving the conjugate variable in which the photons are distinguishable. Our experimental findings agree with theoretical predictions. We contrast our results with a non-spatially resolved measurement where averaging over the photons’ positions washes out the quantum interference observed in spatially resolved measurements.