In a quantum Cheshire cat, one property of a particle is present detached from the particle itself, just as the grin of the feline in Alice in Wonderland can exist in the absence of the whole animal. Now a research team has successfully separated a single photon from its polarization. The effect was previously demonstrated with neutrons and also with light in a classical scenario, but the latest experiment uses single photons.
To produce the Cheshire cat, Maximilian Schlosshauer and his colleagues at the University of Portland in Oregon used an interferometer where light hits a beam splitter, goes in two, opposite directions around a circuit (but along slightly offset routes), and then recombines at the entrance. The incoming polarization of light was horizontal, but this was switched to vertical for the counterclockwise loop. Each path included a device to adjust the polarization further and another to scatter away a small number of photons of a designated polarization, the equivalent of detecting their presence.
To read more, click here.