Generation of Schr\"{o}dinger cat states with Wigner negativity using continuous-wave low-loss waveguide optical parametric amplifier

TL;DR

This paper demonstrates the generation of Schr"{o}dinger cat states with Wigner negativity using a continuous-wave waveguide optical parametric amplifier, advancing practical quantum computing with optical continuous variables.

Contribution

First observation of Wigner negativity in states generated by a waveguide OPA, showing its potential for quantum computing applications.

Findings

Generated Schr"{o}dinger cat states at 1545 nm with Wigner negativity.

Used a ZnO-doped periodically poled LiNbO3 waveguide module.

Waveguide OPA can produce high-purity squeezed states for quantum computing.

Abstract

Continuous-wave (CW) squeezed light is used in generation of various optical quantum states 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 Schr\"{o}dinger cat states at the wavelength of 1545 nm with Wigner negativity using a quasi-single-mode ZnO-doped periodically poled ${\rm LiNbO_3}$ 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.