Polarization-entangled photon pairs generated in aperiodically-poled KTP

We demonstrate polarization-entangled photon-pair generation in aperiodically poled KTiOPO4 (aPPKTP). The aperiodic poling allows two simultaneous downconversion processes corresponding to |HV ⟩ and |V H⟩ signal-idler states. Using a 775 nm pump, we obtained signal and idler at 1530.6 nm and 1569.8 nm, respectively. After compensating for the relative phase between the |HV ⟩ and |V H⟩ states, we obtain polarization entanglement visibilities greater than 0.98 using both pulsed and continuous-wave pumping. This compensation process is important because the relative phase is fixed by the poling pattern. These polarization-entangled photons are useful for distribution of entanglement across a quantum network.