What is nonlocal in counterfactual quantum communication?

Abstract

We revisit the "counterfactual quantum communication" of Salih et al. [1], who claim that an observer "Bob" can send one bit of information to a second observer "Alice" without any physical particle traveling between them. We show that a locally conserved, massless current - specifically, a current of modular angular momentum, $L_z$ mod 2$\hslash$ - carries the one bit of information. We integrate the flux of $L_z$ mod 2$\hslash$ from Bob to Alice and show that it equals one of the two eigenvalues of $L_z$ mod 2$\hslash$, either 0 or $\hslash$, thus precisely accounting for the one bit of information he sends her. We previously [2] obtained this result using weak values of $L_z$ mod 2$\hslash$; here we do not use weak values.

arXiv commentPhysical Review Letters, in press

References in corpus (4)

• Protocol for direct counterfactual quantum communication
• Quantum Cheshire Cats
• Observation of a quantum Cheshire Cat in a matter wave interferometer experiment
• A Current of the Cheshire Cat's Smile: Dynamical Analysis of Weak Values

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• Is the dynamical quantum Cheshire cat detectable?