Entangling Schrödinger's cat states by bridging discrete- and continuous-variable encoding
Journal article, 2025
In quantum information processing, two primary research directions have emerged: one based on discrete variables (DV) and the other on the structure of quantum states in a continuous-variable (CV) space. Integrating these two approaches could unlock new potentials, overcoming their respective limitations. Here, we show that such a DV-CV hybrid approach, applied to superconducting Kerr parametric oscillators (KPOs), enables us to entangle a pair of Schr & ouml;dinger's cat states by two methods. The first involves the entanglement-preserving conversion between Bell states in the Fock-state basis (DV encoding) and those in the cat-state basis (CV encoding). The second method implements a iSWAP\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sqrt{{{{\rm{iSWAP}}}}}$$\end{document} gate between two cat states following the procedure for Fock-state encoding. This simple and fast gate operation completes a universal quantum gate set in a KPO system. Our work offers powerful applications of DV-CV hybridization and marks a first step toward developing a multi-qubit platform based on planar KPO systems.
Author
Daisuke Hoshi
RIKEN Center for Computational Science
Tokyo University of Science
Toshiaki Nagase
Tokyo University of Science
RIKEN Center for Computational Science
Sangil Kwon
Tokyo University of Science
Daisuke Iyama
RIKEN Center for Computational Science
Tokyo University of Science
Takahiko Kamiya
RIKEN Center for Computational Science
Tokyo University of Science
Shiori Fujii
Tokyo University of Science
RIKEN Center for Computational Science
Hiroto Mukai
Tokyo University of Science
RIKEN Center for Computational Science
Shahnawaz Ahmed
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Anton Frisk Kockum
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Shohei Watabe
Shibaura Institute of Technology
Tokyo University of Science
Fumiki Yoshihara
Tokyo University of Science
Jaw-Shen Tsai
RIKEN Center for Computational Science
Tokyo University of Science
Nature Communications
2041-1723 (ISSN) 20411723 (eISSN)
Vol. 16 1 1309Open Superconducting Quantum Computers (OpenSuperQPlus)
European Commission (EC) (EC/HE/101113946), 2023-03-01 -- 2026-08-31.
Giant atoms - a new regime in quantum optics
Swedish Research Council (VR) (2019-03696), 2020-01-01 -- 2023-12-31.
Quantum simulation and communication with giant atoms
Swedish Foundation for Strategic Research (SSF) (FFL21-0279), 2022-08-01 -- 2027-12-31.
Subject Categories (SSIF 2025)
Subatomic Physics
DOI
10.1038/s41467-025-56503-8
PubMed
39900944