There are three condensed matter and quantum information seminars, which are announced via mailing lists.
Anonye interested can join the lists at the links below. Note that many people will automatically receive the announcement via institute lists.

Condensed matter theory seminar, Tue. 16:00.
Organizer: Prof. Walter Selke.
cmtheoseminar@lists.rwth-aachen.de
Join

Condensed matter experiment seminar, Thu. 11:45 and variable time.
Organizer: Prof. Uwe Klemradt
cmexpseminar@lists.rwth-aachen.de
Join

Quantum information seminar, variable time.
Organizer: Prof.  Barbara Terhal
qiseminar@lists.rwth-aachen.de
Join

These lists will also be used occasionally to broadcast seminar announcements that do not fall into one of the categories.  People interested in all three seminars should sign up for the cmseminar@list.rwth-aachen.de list, which includes the above three.

Information about the colloquium can be found here.