Entangling Schrödinger’s cat states by bridging discrete- and continuous-variable encoding
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 Schrödinger'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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt><mml:mrow><mml:mi>iSWAP</mml:mi></mml:mrow> </mml:msqrt> </mml:math> 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.
Authors
- Fumiki Yoshihara
- Shohei Watabe (ORCID: https://orcid.org/0000-0003-2895-698X)
- Shahnawaz Ahmed (ORCID: https://orcid.org/0000-0003-1145-7279)
- Shiori Fujii
- Anton Frisk Kockum (ORCID: https://orcid.org/0000-0002-2534-3021)
- Hiroto Mukai (ORCID: https://orcid.org/0000-0001-6689-7963)
- Toshiaki Nagase
- Daisuke Iyama
- Daisuke Hoshi
- Takahiko Kamiya
- Sangil Kwon (ORCID: https://orcid.org/0000-0002-8113-0821)
- Jaw-Shen Tsai
Institutions
- Tokyo University of Science (JP)
- Shibaura Institute of Technology (JP)
- RIKEN Center for Advanced Photonics (JP)
- RIKEN Center for Quantum Computing
- Chalmers University of Technology (SE)
Publication Details
- Journal
- Nature Communications
- Published
- 2025-02-03
- DOI
- https://doi.org/10.1038/s41467-025-56503-8
- Citations
- 11
- Primary Topic
- Quantum Information and Cryptography
- Type
- article
- Field-Weighted Citation Impact
- 27.29
Funders
- Stiftelsen för Strategisk Forskning
- New Energy and Industrial Technology Development Organization
- Knut och Alice Wallenbergs Stiftelse
- Vetenskapsrådet
- National Astronomical Observatory of Japan
- HORIZON EUROPE Framework Programme
- Japan Science and Technology Agency
- Wallenberg Centre for Molecular and Translational Medicine
- Wallenberg Center for Quantum Technology, Chalmers University of Technology
- Core Research for Evolutional Science and Technology
- Moonshot Research and Development Program