Generation of Schrödinger cat states with Wigner negativity using a continuous-wave low-loss waveguide optical parametric amplifier

• Published in: Optics express Vol. 30; no. 9; pp. 14161 - 14171
• Main Authors: Takase, Kan, Kawasaki, Akito, Jeong, Byung Kyu, Endo, Mamoru, Kashiwazaki, Takahiro, Kazama, Takushi, Enbutsu, Koji, Watanabe, Kei, Umeki, Takeshi, Miki, Shigehito, Terai, Hirotaka, Yabuno, Masahiro, China, Fumihiro, Asavanant, Warit, Yoshikawa, Jun-Ichi, Furusawa, Akira
• Format: Journal Article
• Language: English
• Published: United States 25.04.2022
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.454123

Continuous-wave (CW) squeezed light is used in the generation of various optical quantum states, and thus is a fundamental resource of fault-tolerant universal quantum computation using optical continuous variables. To realize a practical quantum computer, a waveguide optical parametric amplifier (OPA) is an attractive CW squeezed light source in terms of its THz-order bandwidth and suitability for modularization. The usages of a waveguide OPA in quantum applications thus far, however, are limited due to the difficulty of the generation of the squeezed light with a high purity. In this paper, we report the first observation of Wigner negativity of the states generated by a heralding method using a waveguide OPA. We generate Schrödinger cat states at the wavelength of 1545 nm with Wigner negativity using a quasi-single-mode ZnO-doped periodically poled LiNbO waveguide module we developed. Wigner negativity is regarded as an important indicator of the usefulness of the quantum states as it is essential in the fault-tolerant universal quantum computation. Our result shows that our waveguide OPA can be used in wide range of quantum applications leading to a THz-clock optical quantum computer.