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Single‐Particle Entanglement
Author(s) -
Azzini Stefano,
Mazzucchi Sonia,
Moretti Valter,
Pastorello Davide,
Pavesi Lorenzo
Publication year - 2020
Publication title -
advanced quantum technologies
Language(s) - English
Resource type - Journals
ISSN - 2511-9044
DOI - 10.1002/qute.202000014
Subject(s) - quantum entanglement , physics , squashed entanglement , quantum mechanics , entanglement witness , quantum key distribution , degrees of freedom (physics and chemistry) , photon , w state , multipartite entanglement , photon entanglement , quantum
This review is about single‐particle entanglement. Entanglement occurs when the state of a quantum system with at least two degrees of freedom has a particular non‐separable form. In the case of single‐particle entanglement, this quantum correlation is shared by the same particle being it a photon, a neutron, an ion, or an atom. Here, the basics of quantum entanglement are discussed focusing on the case it is related to the degrees of freedom of a single particle. It is discussed how the violation of peculiar inequalities in this context rules out any realistic non‐contextual hidden variable theory alternative to quantum mechanics. Moreover, experiments that demonstrate single‐particle entanglement for photons, neutrons, and atoms are discussed. Finally, the applications of single‐particle entanglement as a resource for quantum information are discussed and specifically quantum key distribution is detailed, where the use of single‐particle entangled photons allows to improve the security of the BB84 protocol.