1) Some basics: So far, how many kninds of entanglement are there? I mean, for multipartite entangled states, we know both W state and GHZ state. I just want to know their properties.

2) How to generate photon-photon pair? How many methods are there available so far? At least for SSPDC method, we can have two ways.

3) How to generate atom-atom entangled pair? Details are needed for different cases.

4) How to generate photon-atom entangled pair? Details are needed for different cases.

5) In above cases, what are the key experimental techniques?