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Genuine Multipartite Entanglement in Time

by Simon Milz, Cornelia Spee, Zhen-Peng Xu, Felix A. Pollock, Kavan Modi, Otfried Gühne

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Submission summary

Authors (as registered SciPost users): Otfried Gühne · Simon Milz
Submission information
Preprint Link:  (pdf)
Date accepted: 2021-05-28
Date submitted: 2021-05-19 09:46
Submitted by: Milz, Simon
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
  • Quantum Physics
Approach: Theoretical


While spatial quantum correlations have been studied in great detail, much less is known about the genuine quantum correlations that can be exhibited by temporal processes. Employing the quantum comb formalism, processes in time can be mapped onto quantum states, with the crucial difference that temporal correlations have to satisfy causal ordering, while their spatial counterpart is not constrained in the same way. Here, we exploit this equivalence and use the tools of multipartite entanglement theory to provide a comprehensive picture of the structure of correlations that (causally ordered) temporal quantum processes can display. First, focusing on the case of a process that is probed at two points in time -- which can equivalently be described by a tripartite quantum state -- we provide necessary as well as sufficient conditions for the presence of bipartite entanglement in different splittings. Next, we connect these scenarios to the previously studied concepts of quantum memory, entanglement breaking superchannels, and quantum steering, thus providing both a physical interpretation for entanglement in temporal quantum processes, and a determination of the resources required for its creation. Additionally, we construct explicit examples of W-type and GHZ-type genuinely multipartite entangled two-time processes and prove that genuine multipartite entanglement in temporal processes can be an emergent phenomenon. Finally, we show that genuinely entangled processes across multiple times exist for any number of probing times.

List of changes

We followed the referees' suggestions and fixed a typo in the conclusions (commuting -> communicating) and emphasized in Sec. 6 that entanglement in the reduced combs does not imply genuine multipartite entanglement in the overall comb

Published as SciPost Phys. 10, 141 (2021)

Reports on this Submission

Anonymous Report 1 on 2021-5-25 (Contributed Report)


I highly recommend the paper for publication in SciPost Physics.

  • validity: top
  • significance: top
  • originality: top
  • clarity: top
  • formatting: perfect
  • grammar: perfect

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