Comment on "Observing the "quantum Cheshire cat" effect with noninvasive weak measurement''

TL;DR

This paper critiques a recent claim of observing the Quantum Cheshire Cat effect, arguing that the experimental setup was inadequate for proper weak measurements and that the results do not definitively demonstrate the effect.

Contribution

The authors provide a critical analysis showing that the recent experimental claim of observing the Quantum Cheshire Cat effect is not substantiated due to methodological issues.

Findings

The experimental setup failed to measure all necessary weak values.

Some weak values were obtained indirectly, not directly from the same setup.

The claim of observing the Quantum Cheshire Cat effect is disputed.

Abstract

In a very recent work [arXiv:2004.07451], Kim et al claimed to have made the first genuine experimental observation of the Quantum Cheshire Cat effect. We dispute this claim on the ground that the setup employed is not adequate for making the weak measurements that define this interferometric effect. Half of the necessary weak values are not observed, and the other half is obtained indirectly by combining results measured with distinct setups.