Demonstration of tripartite cat states in two distinct classes of entanglement
Abstract
Entanglement is a cornerstone of quantum mechanics and an essential resource for quantum computation, communication, and metrology. While bipartite entanglement is extensively studied, genuine multipartite entangled states remain largely inaccessible in the continuous-variable domain. Here, we experimentally realize continuous-variable tripartite entangled cat states of the two distinct classes with fundamentally inequivalent properties, namely GHZ-cat and W-cat states, encoded across three microwave resonators coupled to an ancillary superconducting transmon. We develop one-to-all conditional controls on the three oscillators by fully utilizing three energy levels of the transmon to generate these states in a single piece of hardware and employ an efficient subspace tomography protocol for state reconstruction. We obtain measurement-corrected state fidelities of 0.83±0.02 for GHZ-cat and 0.70±0.02 for W-cat, both exceeding the thresholds for genuine multipartite entanglement, with the W-state certification further supported by an optimized fully decomposable witness directly computed with the reconstructed density matrix. We validate the distinct entanglement classes by experimentally demonstrating that pairwise entanglement is present in the W-cat state but absent in the GHZ-cat state. Our technique for the on-demand generation and characterization of inequivalent classes of tripartite continuous-variable entanglement provides a testbed for studying multipartite bosonic entanglement and its robustness to loss, and a building block for future quantum information processing with multipartite bosonic codes.
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BibTeX
@misc{loke2026demonstration,
title = {{Demonstration of tripartite cat states in two distinct classes of entanglement}},
author = {May Chee Loke and Jonathan Schwinger and Kehui Yu and Yingshan Zhang and Amon M. Kasper and Tanjung Krisnanda and Yvonne Y. Gao},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.12317},
eprint = {2607.12317},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.12317},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Demonstration of tripartite cat states in two distinct classes of entanglement
AU - May Chee Loke
AU - Jonathan Schwinger
AU - Kehui Yu
AU - Yingshan Zhang
AU - Amon M. Kasper
AU - Tanjung Krisnanda
AU - Yvonne Y. Gao
PY - 2026
DA - 2026/10/21
PB - arXiv
DO - 10.48550/arxiv.2607.12317
UR - https://arxiv.org/abs/2607.12317
AB - Entanglement is a cornerstone of quantum mechanics and an essential resource for quantum computation, communication, and metrology. While bipartite entanglement is extensively studied, genuine multipartite entangled states remain largely inaccessible in the continuous-variable domain. Here, we experimentally realize continuous-variable tripartite entangled cat states of the two distinct classes with fundamentally inequivalent properties, namely GHZ-cat and W-cat states, encoded across three microwave resonators coupled to an ancillary superconducting transmon. We develop one-to-all conditional controls on the three oscillators by fully utilizing three energy levels of the transmon to generate these states in a single piece of hardware and employ an efficient subspace tomography protocol for state reconstruction. We obtain measurement-corrected state fidelities of 0.83±0.02 for GHZ-cat and 0.70±0.02 for W-cat, both exceeding the thresholds for genuine multipartite entanglement, with the W-state certification further supported by an optimized fully decomposable witness directly computed with the reconstructed density matrix. We validate the distinct entanglement classes by experimentally demonstrating that pairwise entanglement is present in the W-cat state but absent in the GHZ-cat state. Our technique for the on-demand generation and characterization of inequivalent classes of tripartite continuous-variable entanglement provides a testbed for studying multipartite bosonic entanglement and its robustness to loss, and a building block for future quantum information processing with multipartite bosonic codes.
ER -