Broadband Continuous-wave Optical Quadrature Squeezer for Ultra-fast Optical Quantum Computers

An optical quadrature squeezer is expected to be a key device for high-speed optical quantum computing. We developed a high-gain and broadband optical quadrature squeezer by using a periodically poled lithium niobate (PPLN) waveguide. The squeezer is assembled as a pump-combiner-integrated module with four optical-fiber input/output ports. By improving the fabrication processes of the PPLN waveguide, we achieved a low-loss module that exhibits about 1-dB optical loss. By using this module, we successfully obtained continuous-wave 6-dB-squeezed light at over-6-THz sideband frequency even in a fiber-closed optical system with commercially available optical components. This fiber-compatible broadband quadrature squeezer will accelerate the development of optical quantum computers. © 2022 Nippon Telegraph and Telephone Corp.. All rights reserved.