  We describe the construction and operation of a two-channel noise detection
system for measuring power and cross spectral densities of current fluctuations
near 2 MHz in electronic devices at low temperatures. The system employs
cryogenic amplification and fast-Fourier-transform based spectral measurement.
The gain and electron temperature are calibrated using Johnson noise
thermometry. Full shot noise of 100 pA can be resolved with an integration time
of 10 s. We report a demonstration measurement of bias-dependent current noise
in a gate defined GaAs/AlGaAs quantum point contact.
