  We have contacted single-walled carbon nanotubes after aligning the tubes by
the use of surface acoustic waves. The acoustoelectric current has been
measured at 4.2 K and a probing of the low-dimensional electronic states by the
surface acoustic wave has been detected. By decreasing the acoustic wavelength
resulting in an adjustment to the length of the defined carbon nanotube
constriction a quantization of the acoustoelectric current has been observed.
