  We report highly tunable control of holes in Ge/Si core/shell nanowires
(NWs). We demonstrate the ability to create single quantum dots (QDs) of
various sizes, with low hole occupation numbers and clearly observable excited
states. For the smallest dot size we observe indications of single-hole
occupation. Moreover, we create double and triple tunnel-coupled quantum dot
arrays. In the double quantum dot configuration we observe Pauli spin blockade
(PSB). These results open the way to perform hole spin qubit experiments in
these devices.
