Actually, according to the Neil's Bohr interpretation of quantum theory, which is the prevailing interpretation, the photon has no direction and does not propagate through space. At "birth" there is only a quantum probability field which is only a mathematical abstraction without what we would think of as a physical presence. The means of restricting the possible direction, which where mentioned in the previous post, are only parameters that restrict the probabilities.

When there is a point of possible interaction, such as the presence of an electron at one of the highest probable positions for photon occurrence, then the photon actualizes. It is the actual testing for a photon that can determine which of several paths the photon would be associated with even though it never propagated along that path. If the photon continues it is again reduced to a new quantum probability field with different possibilities. This is the basis for the uncertainty principle.

If this concept troubles you, you are not alone as many Nobel prize holders in physics, starting with Albert Einstein up through present time with Frank Wilczek, have not accepted this concept. Never the less the concepts of non-locality and detection induced quantum field collapse are generally regarded as the most accepted mainstream interpretation.

I have an hour long lecture and demonstration on this subject. If its not breaking any rules I will try and post a link in the new theories section, although no new theories are introduced.