New time-bin entanglement scheme based on a type-II PPLN waveguide
Résumé
We report the realization of a fiber-coupled time-bin entangled photon-pair source at 1538 nm. Unlike previous time-bin sources based on type-0 spontaneous parametric down conversion, our approach takes advantage of cross-polarized paired photons generated in a type-II periodically poled lithium niobate waveguide (PPLN/W). Here, we use a birefringent delay line (BDL) in a Michelson configuration to introduce a controllable delay between the paired photons. After the BDL, these photons are separated by a polarizing beam splitter (PBS) at 45° and sent to Alice and Bob. This way we create the non common time-bin entangled Bell state |Ψ ⟩ = 1/√2 [|s,l⟩ + |l,s⟩], where s and l represent the short and long time-bins, respectively.