Visibility Stokes parameters as a foundation for quantum information science with undetected photons

Abstract

The phenomenon of induced coherence without induced emission allows to reconstruct the quantum state of a photon that remains undetected. The state information is transferred to its partner photon via optical coherence. Using this phenomenon, a number of established quantum information protocols could be adapted for undetected photons. Despite partial attempts, no general procedure for such adaptation exists. Here we shed light on the matter by showing the close relation between two very dissimilar techniques, namely the quantum state tomography of qubits and the recently developed quantum state tomography of undetected photons. We do so by introducing a set of parameters that quantify the coherence and that mimic the Stokes parameters known from the polarization state tomography. We also perform a thorough analysis of the environment of undetected photons and its role in the reconstruction process.