by Monica Sand



The video QBT was produced at the National Supercomputer center and the Department of Physics and Measurement Technology at Linkšping university. Project leader was professor Karl-Fredrik Berggren.
The video is a visualisation of quantum mechanical currents and charge distributions in microcosmos. In the world of quantum physics a particle appears both as particle and wave. The example we see here concerns electric current and charge in a very small conducting cross, a quantum cross manufactured from semiconducting materials ("quantum chips"), The electrical conductors are so thin and cold, that the electrons which constitute the electric current no longer behave like pointlike charges. Instead they behave in a manner similar to light-waves, which can extinguish or amplify each other.

The continuing miniaturisation of electronic components, and the evermore dense packing on microchips mean that phenomena like these will be part of tomorrow's electronics. The video shows the quantum mechanical distribution of charge and currents in the quantum cross. The fundamental mathematical model is rather sterile, it is almost impossible to predict the prominent vortex shown in the video. Nor is a table of numbers very illustrative. Only when we make a sequence of pictures will the underlying physics come to life. An animation can demonstrate how the current vortices dance around when external conditions like energy or voltage.

I have used the video in two different installations:
"Guides Lumierers" in the Swedish pavilion at the expo in Seville 1992, and "IntrŠde", ("Entrance") at an educational exhibition held in Sollentuna, close to Stockholm 1995.

In Seville the video was used as a stationary background for non moving objects. The objects were 7 light-guides from CERN, Geneva.
In Sollentuna 8 video screens formed an entrance hallway. At the end of the hallway the visitor met a black "altarpiece" with a big screen version of the video with two light guides as guardian angels.

The video sequence in the hallway show the probability for an electron to be at a given position and at a given energy in the quantum cross.
Red means large probability.
The video sequence in the hallway demonstrates a probable flow (velocity) of the electron at different energies, different colours indicate different velocities. .