  A single photon is well known to have spin S = hbar, which would correspond
to circular polarization, and all quantum transitions with photon absorption or
emission correspond to DeltaS = +/-hbar. However, it is also widely believed
that a single photon may be linearly polarized, which would correspond to a
state with S = 0. Indeed, linearly polarized single photons are central to most
quantum entanglement experiments. On the contrary, it has recently been
suggested (based on a realistic spin-quantized wave picture of quantum states)
that a linearly polarized photon state must be a superposition of a pair of
circularly polarized photons, each with S = +/-hbar. This question cannot be
resolved using a conventional photon detector, which generally cannot
distinguish one photon from two simultaneous photons. However, it can be
addressed using a superconducting microcalorimeter detector with sub-eV energy
resolution and high quantum efficiency (QE). A careful experiment demonstrating
this photon pairing could place in question some of the paradoxical central
foundations of modern quantum theory, including quantum entanglement and
nonlocality.
