  Balanced homodyne detector (BHD) that can measure the field quadratures of
coherent states has been widely used in a range of quantum information
technologies. Generally, the BHD tends to suffer from narrow bands and an
expanding bandwidth behavior usually traps into a compromise with the gain,
electronic noise, and quantum to classical noise ratio, etc. In this paper, we
design and construct a wideband BHD based on radio frequency and integrated
circuit technology. Our BHD shows bandwidth behavior up to 1.2 GHz and its
quantum to classical noise ratio is around 18 dB. Simultaneously, the BHD has a
linear performance with a gain of 4.86k and its common mode rejection ratio has
also been tested as 57.9 dB. With this BHD, the secret key rate of
continuous-variable quantum key distribution system has a potential to achieve
66.55 Mbps and 2.87 Mbps respectively at the transmission distance of 10 km and
45 km. Besides, with this BHD, the generation rate of quantum random number
generator could reach up to 6.53Gbps.
