  We report on charge sensing measurements of a GaAs semiconductor quantum dot
device using a radio frequency quantum point contact (rf-QPC). The rf-QPC is
fully characterized at 4 K and milli-Kelvin temperatures and found to have a
bandwidth exceeding 20 MHz. For single-shot charge sensing we achieve a charge
sensitivity of 2x10^-4 e/(sqrt)Hz referred to the neighboring dot's charge. The
rf-QPC compares favorably with rf-SET electrometers and promises to be an
extremely useful tool for characterizing and measuring semiconductor quantum
systems on fast timescales.
