Quantum communication protocols have been studied widely in recent years. Quantum key distribution (QKD) can be used for quantum communication to share information key between two locations with security supported by quantum theory. The information key can be used to transfer information securely from one to the other between the two locations using the distributed key for one time pad. The QKD can be implemented using entangled photon pairs as the light source. To improve the generation efficiency, we have developed schemes to entangled all of the generated photon pairs. I will talk about those methods with experimental results also with preliminary demonstration experiment results for QKD.