Past of a particle in an entangled state

Dilip Paneru, Eliahu Cohen*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

10 Citations (Scopus)
214 Downloads (Pure)


Vaidman has proposed a controversial criterion for determining the past of a single quantum particle based on the “weak trace” it leaves. We here consider more general examples of entangled systems and analyze the past of single, as well as pairs of entangled pre- and postselected particles. Systems with nontrivial time evolution are also analyzed. We argue that in these cases, examining only the single-particle weak trace provides information which is insufficient for understanding the system as a whole. We therefore suggest to examine, alongside with the past of single particles, also the past of pairs, triplets and eventually the entire system, including higher-order, multipartite traces in the analysis. This resonates with a recently proposed top-down approach by Aharonov, Cohen and Tollaksen for understanding the structure of correlations in pre- and postselected systems.

Original languageEnglish
Article number1740019
Number of pages11
JournalInternational Journal of Quantum Information
Publication statusPublished - 22 Dec 2017


  • entanglement
  • Past of a quantum particle
  • quantum nonlocality
  • weak values


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