The University of Amsterdam campus can easily be reached by train. From Schiphol airport take any train to Amsterdam Centraal and then change onto the Sprinter train for Zwolle or for Amersfoort Vathorst. Leave the train on the second stop: Amsterdam Science Park. Trains from Schiphol to Amsterdam Centraal are extremely frequent, while the Sprinter for Science Park departs every 15m. The whole travel takes around 40m.
Tickets can be bought at the yellow self-service machines present in every station. Alternatively you can buy tickets on the website https://www.ns.nl/en. Note that tickets are not valid for specific trains: with a given ticket you can take any train between the two stations.
On the last day of the conference we will organize a bus going from the congress center to Schipol airport. In case you need to reach the airport using public transport there are two possibilities. From Lunteren station you can take the Stoptrein for Amersfoort and there change onto the Intercity train for Schiphol airport. Alternatively from Lunteren station take the Stoptrein for Ede-Wageningen and then the Intercity for Schipol airport. Both routes take around 1h30m and depart every 30m.