  We present a realisation of high bandwidth instrumentation at cryogenic
temperatures and for dilution refrigerator operation that possesses advantages
over methods using radio-frequency single electron transistor or transimpedance
amplifiers. The ability for the low temperature electronics to carry out faster
measurements than with room temperature electronics is investigated by the use
of a phosphorous-doped single-electron transistor. A single-shot technique is
successfully implemented and used to observe the real time decay of a quantum
state. A discussion on various measurement strategies is presented and the
consequences on electron heating and noise are analysed.
