Optimized real-time homodyne detection of bright pico-second twin beams by digital signal processing

Twin beams are useful tools in quantum technologies. However, due to their asymmetry in photon number distribution, a scheme needs to be optimized in order to fully exploit their quantum advantage. Here, we demonstrate a detection scheme for bright pico-second twin beams generated from a fiber optical parametric amplifier, in which the electronic gain of the detecting process is optimized in real time by digital signal processing without accurately calibrating the detection channels. Twin beams of -7.5 dB intensity difference squeezing (IDS) (the highest in an optical fiber system) is generated at a brightness of about 0.1 W in peak power. Our result paves the way for applications of twin beams in time-varying channels with asymmetric loss or noise.