There are on this site a few questions about photons and circular polarization, but none of them give satisfactory answers:
I have read this question:
Where annav says:
This illustration explains how the photons, which can only have spin +1 or -1 to their direction of momentum, build up a polarized beam
where Sean E. Lake says:
"As there exist no circularly polarized photons" That seems incorrect, since circularly polarized photons are photons of definite helicity, which is just spin measured along the direction or propagation. The different polarization states would correspond, in principle, to measuring spin along different axes than the propagation one, I think.
And from wiki:
In the quantum mechanical view, light is composed of photons. Polarization is a manifestation of the spin angular momentum of light. More specifically, in quantum mechanics the direction of spin of a photon is tied to the handedness of the circularly polarized light and the spin of a beam of photons is similar to the spin of a beam of particles, such as electrons.
An individual photon can be described as having right or left circular polarization, or a superposition of the two.
Now this one specifically states that single photons do have polarization and can have circular polarization:
Now these are two different explanations, as the former describes photons as QM entities, that on their own can only have spin of 1 or -1, that's it. In this description, only the confluent classical EM wave, being built up by a large number of photons, can have circular polarization.
But the latter describes photons as QM entities, and even single photons as having circular polarization of their own.
The closest to this topic, I have found in another question on this site, which describes orbital angular momentum:
This describes single photons as having OAM (in addition to spin or helicity), but one of the answers says it does exist for single photons, it is just hardly measurable. The other answer states the opposite, saying that since photons are in potential wells, and not orbits, there is no OAM for single photons.
So there are two completely opposing views, these are:
single photons are QM entities, but all they can have is simply a spin of 1 or -1, that's it, single photons cannot have circular polarization on their own, only the classical EM wave they build up can have it
single photons are QM entities, and even so they can possess superposition of polarization (circular polarization is a superposition of linear)
- Can a single photon have circular polarization?