Nonclassical oscillations in pre- and post-selected quantum walks

Xiao-Xiao Chen, Zhe Meng, Jian Li, Jia-Zhi Yang, An-Ning Zhang, Tomasz Kopyciuk, and Paweł Kurzyński
Phys. Rev. A 104, 012220 – Published 28 July 2021
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Abstract

Quantum walks are counterparts of classical random walks. They spread faster, which can be exploited in information processing tasks, and constitute a versatile simulation platform for many quantum systems. Yet, some of their properties can be emulated with classical light. This raises a question: which aspects of the model are truly nonclassical? We address it by carrying out a photonic experiment based on a pre- and post-selection paradox. The paradox implies that if somebody could choose to ask either if the particle is at position x=0 at even time steps or at position x=d (d>1) at odd time steps, the answer would be positive, no matter the question asked. Therefore, the particle seems to undergo long distance oscillations despite the fact that the model allows it to jump one position at a time. We translate this paradox into a Bell-like inequality and then into a contextuality witness. Finally, we experimentally verify this witness up to eight standard deviations.

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  • Received 31 January 2021
  • Accepted 9 July 2021

DOI:https://doi.org/10.1103/PhysRevA.104.012220

©2021 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalQuantum Information, Science & TechnologyGeneral Physics

Authors & Affiliations

Xiao-Xiao Chen1, Zhe Meng1, Jian Li1, Jia-Zhi Yang1, An-Ning Zhang1,*, Tomasz Kopyciuk2, and Paweł Kurzyński3,†

  • 1Center for Quantum Technology Research and Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Haidian District, Beijing 100081, People's Republic of China
  • 2Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland
  • 3Institute of Spintronics and Quantum Information, Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland

  • *anningzhang@bit.edu.cn
  • pawel.kurzynski@amu.edu.pl

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Issue

Vol. 104, Iss. 1 — July 2021

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