Public exhibit for demonstrating the quantum of electrical conductance
  We present a new robust setup that explains and demonstrates the quantum of electrical conductance for a general audience and which is continuously available in a public space. The setup allows users to manually thin a gold wire of several atoms in diameter while monitoring its conductance in real time. During the experiment, a characteristic step-like conductance decrease due to rearrangements of atoms in the cross-section of the wire is observed. Just before the wire breaks, a contact consisting of a single atom with a characteristic conductance close to the quantum of conductance can be maintained up to several seconds. The setup is operated full-time, needs practically no maintenance and is used on different educational levels. 
E.H. Huisman, F.L. Bakker, J.P. van der Pal, R.M. de Jonge, C.H. van   der Wal
physics.pop-ph cond-mat.mes-hall