There are two major challenges in the development of quantum computers: scalability and fault tolerance. In the optical system, a scalable quantum computing platform has already been developed, thus realization of fault tolerance has been a major issue. In 2024, the generation of optical logical qubits, a key step toward fault tolerance, was reported by Furusawa’s group in the University of Tokyo. However, previous schemes had low generation rates, making them impractical for real-world applications.
This research expands the bandwidth of quantum light sources from MHz to 6 THz and improved homodyne detectors from 100 MHz to 70 GHz by utilizing waveguide optical parametric amplifiers and 5G-telecommunication technologies. These enhancements allow them to generate non-classical quantum states, called Schrödinger’s cat states, at a rate of 1 MHz—1,000 times faster than previous methods. The generated quantum states can also be used as resources for logical qubit generation, and these advancements are critical steps toward practical, high-speed, fault-tolerant quantum computing systems.
(Left) Picture of optical parametric amplifier. (Center) Wigner function of generated quantum states. (right) temporal mode function of generated quantum states.
Papers
Journal: Nature Communications
Title: Broadband generation and tomography of non-Gaussian states for ultra-fast optical quantum processors
Authors: Akito Kawasaki, Ryuhoh Ide, Hector Brunel, Takumi Suzuki, Rajveer Nehra, Katsuki Nakashima, Takahiro Kashiwazaki, Asuka Inoue, Takeshi Umeki, Fumihiro China, Masahiro Yabuno, Shigehito Miki, Hirotaka Terai, Taichi Yamashima, Atsushi Sakaguchi, Kan Takase, Mamoru Endo, Warit Asavanant*, Akira Furusawa*