The quantum computer exemplifies the superior information processing capacity of quantum physics which is rooted in the notion of entanglement. Everyday matter is made from near-infinities of quantum particles but it turns out that it lost its entanglement properties. However, recently evidences are accumulating that forms of matter exist being genuinely entangled on the macroscopic scale. The search for such forms of "quantum matter" is intensely pursued in Leiden. A main arena are the strongly interacting electron systems realized in special solids and the experimental research revolves around exploring the novel techniques of nanophysics to observe and manipulate these eerie worlds. This field gets quite some propulsion from mathematical advances and the theoretical research concentrates on field theoretical- and quantum informational aspects, and especially the holographic (AdS/CFT) duality discovered in string theory.