"Counterfactual" quantum protocols

L. Vaidman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The counterfactuality of recently proposed protocols is analyzed. A definition of "counterfactuality" is offered and it is argued that an interaction-free measurement (IFM) of the presence of an opaque object can be named "counterfactual", while proposed "counterfactual" measurements of the absence of such objects are not counterfactual. The quantum key distribution protocols which rely only on measurements of the presence of the object are counterfactual, but quantum direct communication protocols are not. Therefore, the name "counterfactual" is not appropriate for recent "counterfactual" protocols which transfer quantum states by quantum direct communication.

Original languageEnglish
Article number1640012
JournalInternational Journal of Quantum Information
Issue number4
StatePublished - 1 Jun 2016


FundersFunder number
German-Israeli Foundation for Scientific Research and DevelopmentI-1275-303.14
Israel Science Foundation1311/14


    • Interaction-free measurement
    • counterfactual communication
    • quantum communication
    • quantum measurement


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