Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:0806.0748 · Physical Review Letters

Generation of High-Fidelity Four-Photon Cluster State and Quantum-Domain Demonstration of One-Way Quantum Computing

Yuuki Tokunaga, Shin Kuwashiro, Takashi Yamamoto, Masato Koashi, Nobuyuki Imoto

Published May 27, 2008• 104 citations
arXivHTMLPDF

Abstract

We experimentally demonstrate a simple scheme for generating a four-photon entangled cluster state with fidelity over 0.860+/-0.015. We show that the fidelity is high enough to guarantee that the produced state is distinguished from Greenberger-Horne-Zeilinger, W, and Dicke types of genuine four-qubit entanglement. We also demonstrate basic operations of one-way quantum computing using the produced state and show that the output state fidelities surpass classical bounds, which indicates that the entanglement in the produced state essentially contributes to the quantum operation.

DOI
10.1103/physrevlett.100.210501

Related papers

Simple experimental generation of a four-photon cluster state and distinguishing classes of genuine four-qubit entanglement using witness operators

Yuuki Tokunaga, Shin Kuwashiro, Takashi Yamamoto +2 more

We experimentally demonstrate a simple scheme for generating a four-photon cluster state. We show that the produced state has genuine four-qubit entanglement which is discriminated from a class including GHZ and W types of entanglement.

Quantum Electronics and Laser Science Conference•May 1, 2007•0 citations

Fidelity estimation and entanglement verification for experimentally produced four-qubit cluster states

Yuuki Tokunaga, Takashi Yamamoto, Masato Koashi +1 more

We propose methods of fidelity estimation and entanglement verification for experimentally produced four-qubit cluster states. We show that we can obtain a high lower bound of the fidelity using only four local projective measurement settings. The lower bound is close to the exact fidelity, which is determined only by at least nine local projective measurement settings. We also present witness operators for distinguishing entanglement around a four-qubit cluster state from specific classes of genuine four-qubit entanglement, e.g., a class including GHZ and $W$ types of entanglement.

Physical Review A•Aug 23, 2006•33 citations

Experimental Observation of Four-Photon Entangled Dicke State with High Fidelity

Nikolai Kiesel, Ch. Schmid, Géza Tóth +2 more

We present the experimental observation of the symmetric four-photon entangled Dicke state with two excitations |D_{4};{(2)}. A simple experimental setup allowed quantum state tomography yielding a fidelity as high as 0.844+/-0.008. We study the entanglement persistency of the state using novel witness operators and focus on the demonstration of a remarkable property: depending on the orientation of a measurement on one photon, the remaining three photons are projected into both inequivalent classes of genuine tripartite entanglement, the Greenberger-Horne-Zeilinger and W class. Furthermore, we discuss possible applications of |D_{4};{(2)} in quantum communication.

arXiv:quant-ph/0606234•Physical Review Letters•Feb 7, 2007•262 citations

Experimental generation of a high-fidelity four-photon linear cluster state

Chao Zhang, Yun‐Feng Huang, Bi‐Heng Liu +2 more

Cluster state plays a crucial role in one-way quantum computation. Here, we propose and experimentally demonstrate a scheme to prepare an ultrahigh-fidelity four-photon linear cluster state via a spontaneous parametric down-conversion process. The state fidelity is measured to be $0.9517\ifmmode\pm\else\textpm\fi{}0.0027$. Our scheme can be directly extended to more photons to generate an $N$-qubit linear cluster state. Furthermore, our scheme is optimal for generating photonic linear cluster states in the sense of achieving the maximal success probability and having the simplest strategy. The key idea is that the photon pairs are prepared in some special nonmaximally entangled states instead of the normal Bell states. To generate a $2N$-qubit linear cluster state from $N$ pairs of entangled photons, only $(N\ensuremath{-}1)$ Hong-Ou-Mandel interferences are needed and a success probability of ${(\frac{1}{4})}^{N\ensuremath{-}1}$ is achieved.

arXiv:1610.00232•Physical Review A•Jun 22, 2016•19 citations

Generation and applications of an ultrahigh-fidelity four-photon Greenberger-Horne-Zeilinger state

Chao Zhang, Yun‐Feng Huang, Chengjie Zhang +4 more

High-quality entangled photon pairs generated via spontaneous parametric down-conversion have made great contributions to the modern quantum information science and the fundamental tests of quantum mechanics. However, the quality of the entangled states decreases sharply when moving from biphoton to multiphoton experiments, mainly due to the lack of interactions between photons. Here, for the first time, we generate a four-photon Greenberger-Horne-Zeilinger state with a fidelity of 98%, which is even comparable to the best fidelity of biphoton entangled states. Thus, it enables us to demonstrate an ultrahigh-fidelity entanglement swapping-the key ingredient in various quantum information tasks. Our results push the fidelity of multiphoton entanglement generation to a new level and would be useful in some demanding tasks, e.g., we successfully demonstrate the genuine multipartite nonlocality of the observed state in the nonsignaling scenario by violating a novel Hardy-like inequality, which requires very high state-fidelity.

arXiv:1702.04130•Optics Express•Nov 14, 2016•27 citations

Experimental Analysis of a Four-Qubit Photon Cluster State

Nikolai Kiesel, Christian Schmid, Ulrich Weber +4 more

Linear-optics quantum logic operations enabled the observation of a four-photon cluster state. We prove genuine four-partite entanglement and study its persistency, demonstrating remarkable differences from the usual Greenberger-Horne-Zeilinger (GHZ) state. Efficient analysis tools are introduced in the experiment, which will be of great importance in further studies on multiparticle entangled states.

arXiv:quant-ph/0508128•Physical Review Letters•Nov 16, 2005•284 citations
We experimentally demonstrate a simple scheme for generating a four-photon entangled cluster state with fidelity over 0.860+/-0.015. We show that the fidelity is high enough to guarantee that the produced state is distinguished from Greenberger-Horne-Zeilinger, W, and Dicke types of genuine four-qubit entanglement. We also demonstrate basic operations of one-way quantum computing using the produced state and show that the output state fidelities surpass classical bounds, which indicates that the entanglement in the produced state essentially contributes to the quantum operation.
We propose methods of fidelity estimation and entanglement verification for experimentally produced four-qubit cluster states. We show that we can obtain a high lower bound of the fidelity using only four local projective measurement settings. The lower bound is close to the exact fidelity, which is determined only by at least nine local projective measurement settings. We also present witness operators for distinguishing entanglement around a four-qubit cluster state from specific classes of genuine four-qubit entanglement, e.g., a class including GHZ and WWW types of entanglement.
We present the experimental observation of the symmetric four-photon entangled Dicke state with two excitations |D_{4};{(2)}. A simple experimental setup allowed quantum state tomography yielding a fidelity as high as 0.844+/-0.008. We study the entanglement persistency of the state using novel witness operators and focus on the demonstration of a remarkable property: depending on the orientation of a measurement on one photon, the remaining three photons are projected into both inequivalent classes of genuine tripartite entanglement, the Greenberger-Horne-Zeilinger and W class. Furthermore, we discuss possible applications of |D_{4};{(2)} in quantum communication.
Cluster state plays a crucial role in one-way quantum computation. Here, we propose and experimentally demonstrate a scheme to prepare an ultrahigh-fidelity four-photon linear cluster state via a spontaneous parametric down-conversion process. The state fidelity is measured to be $0.9517\ifmmode\pm\else\textpm\fi{}0.0027$. Our scheme can be directly extended to more photons to generate an NNN-qubit linear cluster state. Furthermore, our scheme is optimal for generating photonic linear cluster states in the sense of achieving the maximal success probability and having the simplest strategy. The key idea is that the photon pairs are prepared in some special nonmaximally entangled states instead of the normal Bell states. To generate a 2N2N2N-qubit linear cluster state from NNN pairs of entangled photons, only $(N\ensuremath{-}1)$ Hong-Ou-Mandel interferences are needed and a success probability of ${(\frac{1}{4})}^{N\ensuremath{-}1}$ is achieved.
High-quality entangled photon pairs generated via spontaneous parametric down-conversion have made great contributions to the modern quantum information science and the fundamental tests of quantum mechanics. However, the quality of the entangled states decreases sharply when moving from biphoton to multiphoton experiments, mainly due to the lack of interactions between photons. Here, for the first time, we generate a four-photon Greenberger-Horne-Zeilinger state with a fidelity of 98%, which is even comparable to the best fidelity of biphoton entangled states. Thus, it enables us to demonstrate an ultrahigh-fidelity entanglement swapping-the key ingredient in various quantum information tasks. Our results push the fidelity of multiphoton entanglement generation to a new level and would be useful in some demanding tasks, e.g., we successfully demonstrate the genuine multipartite nonlocality of the observed state in the nonsignaling scenario by violating a novel Hardy-like inequality, which requires very high state-fidelity.