Multi-parameter estimation of the state of two interfering photonic qubits

It is demonstrated a two-photon interfering technique based on polarization-resolved measurements for the simultaneous estimation with the maximum sensitivity achievable in nature of multiple parameters associated with the polarization state of two interfering photonic qubits. This estimation is done by exploiting a novel interferometry technique based on polarization-resolved two-photon interference. We show the experimental feasibility and accuracy of this technique even when a limited number of sampling measurements is employed. This work is relevant for the development of quantum technologies with photonic qubits and sheds light on the physics at the interface between multiphoton interference, boson sampling, multi-parameter quantum sensing and quantum information processing.