Comment on "Multitime quantum communication: Interesting but not counterfactual"

TL;DR

This paper critiques a recent analysis of a quantum communication protocol, arguing that the proposed measure of channel usage is inappropriate and does not accurately assess the protocol's counterfactuality.

Contribution

The paper challenges the validity of Griffiths' 'Cost' measure, demonstrating it fails to correctly evaluate the counterfactual nature of the original protocol.

Findings

Griffiths' 'Cost' measure is unsuitable for assessing counterfactuality.

The original interaction-free measurement protocol is not counterfactual under this measure.

The critique clarifies misconceptions about quantum communication protocols.

Abstract

In a recent paper, Robert Griffiths [Phys. Rev. A 107, 062219 (2023)] analyzed a protocol for transmission of information between two parties introduced by Salih et al. [Phys. Rev. Lett. 110, 170502 (2013)]. There is a considerable controversy about the counterfactuality of this protocol, and Griffiths suggested to resolve it by introducing a new measure of channel usage, which he called "Cost". I argue that this measure is not appropriate because the original interaction-free measurement protocol which triggered the definition of the concept of counterfactuality is not counterfactual according to this measure.