Observation of eight-photon entanglement

• Published in: Nature photonics Vol. 6; no. 4; pp. 225 - 228
• Main Authors: Yao, Xing-Can, Wang, Tian-Xiong, Xu, Ping, Lu, He, Pan, Ge-Sheng, Bao, Xiao-Hui, Peng, Cheng-Zhi, Lu, Chao-Yang, Chen, Yu-Ao, Pan, Jian-Wei
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.04.2012
• Subjects: Degrees of freedom; Entangled states; Entanglement; Interferometers; Mathematical analysis; Photons; Qubits (quantum computing); Schroedinger cat state
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/nphoton.2011.354

The creation of increasingly large multipartite entangled states is not only a fundamental scientific endeavour in itself, but is also the enabling technology for quantum information. Tremendous experimental effort has been devoted to generating multiparticle entanglement with a growing number of qubits. So far, up to six spatially separated single photons have been entangled based on parametric downconversion. Multiple degrees of freedom of a single photon have been exploited to generate forms of hyper-entangled states. Here, using new ultra-bright sources of entangled photon pairs, an eight-photon interferometer and post-selection detection, we demonstrate for the first time the creation of an eight-photon Schrödinger cat state with genuine multipartite entanglement. The ability to control eight individual photons represents a step towards optical quantum computation, and will enable new experiments on, for example, quantum simulation, topological error correction and testing entanglement dynamics under decoherence.