  We design and demonstrate a resonant-type differential photodetector for
low-noise quantum homodyne measurement at 500MHz optical sideband with 17MHz of
bandwidth. By using a microwave monolithic amplifier and a discrete voltage
buffer circuit, a low-noise voltage amplifier is realized and applied to our
detector. 12dB of signal-to-noise ratio of the shot noise to the electric noise
is obtained with 5mW of continuous-wave local oscillator. We analyze the
frequency response and the noise characteristics of a resonant photodetector,
and the theoretical model agrees with the shot noise measurement.
