Indistinguishability of entangled photons generated with achromatic phase matching

We put forward a method to suppress distinguishing information contained in the frequency spectrum of entangled photon pairs generated in spontaneous parametric down-conversion. The distinguishing information is shown to be suppressed by employing achromatic phase-matching techniques to tailor the group velocities of the generated signal and idler photons, and thus tuning their spectral properties. The method can be implemented in materials and frequency bands where conventional solutions do not hold, and it can benefit from the dispersion cancellation inherent to entangled photons featuring frequency correlation or anticorrelation. The generation of polarization Bell states is discussed.