  The visibility of the two-photon interference in the Franson interferometer
serves as a measure of the energy-time entanglement of the photons. We propose
to control the visibility of the interference in the second-order coherence
function by implementing a coherent time-delayed feedback mechanism. Simulating
the non-Markovian dynamics within the matrix product state framework, we find
that the visibility for two photons emitted from a three-level system (3LS) in
ladder configuration can be enhanced significantly for a wide range of
parameters by slowing down the decay of the upper level of the 3LS.
