Observation of a classical Cheshire cat in an optical interferometer

Area of Science:

• Quantum mechanics
• Wave-particle duality
• Optical physics

Background:

• A recent neutron interferometry experiment reported a paradoxical phenomenon termed the "quantum Cheshire cat."
• This phenomenon suggests a separation between a particle's path and its property, like polarization.

Purpose of the Study:

• To reproduce and extend the "quantum Cheshire cat" experiment using an optical interferometer.
• To investigate the quantum or classical nature of the observed phenomenon.

Main Methods:

• Utilized an optical interferometer equivalent to the neutron interferometry setup.
• Reproduced and extended the experimental conditions and measurements.

Main Results:

• Observed results consistent with the photon traveling through one interferometer arm and its polarization through another.
• Demonstrated that these results occur in a regime where quantum and classical wave theories overlap.

Conclusions:

• The "quantum Cheshire cat" phenomenon is not uniquely quantum.
• The observed effects can be explained by classical wave theory, indicating no uniquely quantum aspect to this illusion.