Dual to the anomalous weak value effect of photon-polarisation separation

TL;DR

This paper explores a dual to the quantum Cheshire cat effect, revealing a novel interference phenomenon involving photon polarisation, and suggests new experimental avenues to demonstrate disembodied quantum properties.

Contribution

It introduces a dual version of the quantum Cheshire cat, showing a unique interference effect and proposing an alternative experimental approach to observe disembodied quantum properties.

Findings

Zero weak value can be interpreted as linear polarisation

Dual QCC exhibits interference from a phantom arm

Proposes new experimental pathway for QCC demonstration

Abstract

The quantum Cheshire cat (QCC) thought experiment proposes that a quantum object's property (\textit{e.g} polarisation, spin, etc.) can be separated from its physical body or \textit{disembodied}. This conclusion arose from an argument that interprets a zero weak value (WV) of polarisation as no polarisation. We show that this argument is incomplete in the sense that a zero WV reading could equally be interpreted as linear polarisation. Nevertheless, through a generalisation of the QCC, we complete their argument by excluding the possibility of linear polarisation as a consistent interpretation. We go further, and introduce the dual of the generalised QCC. The dual QCC exhibits an intriguing effect, where a horizontally-polarised interferometer with just one arm, can give rise to interference which is vertically-polarised. The interference appears to arise as the result of the phase difference between the physical arm and a \textit{phantom} arm. This peculiar effect arises from the interplay between the pre-selected and post-selected states, which characterises WVs. The QCC has not yet been unambiguously experimentally demonstrated. The QCC dual offers an alternative pathway to experimental realisation.