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Testing Real Quantum Theory in an Optical Quantum Network

Zheng-Da Li1,2,*, Ya-Li Mao1,2,*, Mirjam Weilenmann3, Armin Tavakoli3,4, Hu Chen1,2, Lixin Feng1,2, Sheng-Jun Yang1,2, Marc-Olivier Renou5, David Trillo3 et al.

Thinh P. Le3, Nicolas Gisin6,7, Antonio Acín5,8, Miguel Navascués3, Zizhu Wang (王子竹)9, and Jingyun Fan1,2,†

  • 1Shenzhen Institute for Quantum Science and Engineering and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
  • 2Guangdong Provincial Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
  • 3Institute for Quantum Optics and Quantum Information - IQOQI Vienna, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria
  • 4Institute for Atomic and Subatomic Physics, Vienna University of Technology, 1020 Vienna, Austria
  • 5ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
  • 6Group of Applied Physics, University of Geneva, 1211 Geneva 4, Switzerland
  • 7Schaffhausen Institute of Technology - SIT, 1211 Geneva 4, Switzerland
  • 8ICREA, Pg. Lluis Companys 23, 08010 Barcelona, Spain
  • 9Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China

  • *These authors contributed equally to this work.
  • †Fanjy@sustech.edu.cn
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Phys. Rev. Lett. 128, 040402 – Published 24 January, 2022

DOI: https://doi.org/10.1103/PhysRevLett.128.040402

Abstract

Quantum theory is commonly formulated in complex Hilbert spaces. However, the question of whether complex numbers need to be given a fundamental role in the theory has been debated since its pioneering days. Recently it has been shown that tests in the spirit of a Bell inequality can reveal quantum predictions in entanglement swapping scenarios that cannot be modeled by the natural real-number analog of standard quantum theory. Here, we tailor such tests for implementation in state-of-the-art photonic systems. We experimentally demonstrate quantum correlations in a network of three parties and two independent EPR sources that violate the constraints of real quantum theory by over 4.5 standard deviations, hence disproving real quantum theory as a universal physical theory.

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Quantum Mechanics Must Be Complex

Published 24 January, 2022

Two independent studies demonstrate that a formulation of quantum mechanics involving complex rather than real numbers is necessary to reproduce experimental results.

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Ruling Out Real-Valued Standard Formalism of Quantum Theory

Ming-Cheng Chen, Can Wang, Feng-Ming Liu, Jian-Wen Wang, Chong Ying, Zhong-Xia Shang, Yulin Wu, M. Gong, H. Deng, F.-T. Liang, Qiang Zhang, Cheng-Zhi Peng, Xiaobo Zhu, Adán Cabello, Chao-Yang Lu, and Jian-Wei Pan
Phys. Rev. Lett. 128, 040403 (2022)

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Phys. Rev. Lett. 128, 040402– Published 24 January, 2022
  • Received 27 October 2021
  • Accepted 29 November 2021
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