Photon Polarization / Superposition of States

We can ask ourselves what the subject ‘looks like’, at the single-particle level, of polarized light. We know that at the level of wave-mechanics, both plane-polarized and circularly-polarized light are easy to understand: Either way, the dipole-moments are at right angles to the direction of propagation, all the time, even if randomly so. But there also needs to be a particle / photon -based explanation for all the properties of light, in order to satisfy the demands of Quantum Mechanics.

And so a key question could be phrased as, ‘If we pass randomly-polarized light through a simple linear polarizer, which consists of a gel-block, and which absorbs EM vibrations along one disfavored axis, maybe because it has been made ohmic along that axis, why is the maximum intensity of plane-polarized light that comes out, in fact so close to 50% of the intensity, of the randomly-polarized beam that went in?’ Using wave-mechanics, the answer is easy to see, but using particle-physics, the answer is not so obvious.

And one reason fw the answer may not be obvious, is because we might be visualizing each photon, as being plane-polarized at an angle unique to itself. In that case, if the polarizer only transmits light, which is polarized to an extremely pure degree, the number of photons whose plane of polarization lines up with the favored angle perfectly, should be few-to-none. Each photon could then have an angle of polarization, which is not exactly lined up with the axis which the polarizer favors, and would thus be filtered out. And yet, the strength of the electric dipole-moment which comes out of the polarizer, along the disfavored axis, could be close to zero, while the total amount of light that comes out, could be close to 50% of how much light came in.

If each incident photon had been plane-polarized in one random direction, then surely fewer than 50% of them, would have been polarized, in one exact direction.

(Updated 04/10/2018 … )

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About Why the output of a Laser is so Wavelike

The subject of wave-particle duality continues to mystify commoners, while the ultimate explanation given by experts, who need to be schooled in Quantum-Mechanics for years, before they are exposed to these secrets, seem to defy some common-sense reasoning. More specifically, the way in which Quantum-Mechanics mainly explains it, is that the wave-phenomena, specifically those that take place in a vacuum, only exist as being secondary to the existence of particles. We think we can see many examples in our practical world, where waves ‘seem real’.

One such example is the beam of light output by a Laser, that is both monochromatic and coherent, that is highly parallel, and that only seems to make its wave-nature obvious. It is this ultra-high consistency of the wave-nature of a Laser-beam, that also makes it useful for creating holograms – aside from the fact that the beams output from these devices have many more uses today.

But in a way that might disappoint some skeptical thinkers, this nature of the light output from a Laser is actually predicted by Quantum-Mechanics, and fails to provide a contradiction to it. And I will explain why.

Quantum Mechanics is largely built around the Heisenberg Uncertainty Principle, although Heisenberg did not dare to assign complex numbers to his probability clouds yet. Those probability clouds are supposed to represent the superposed states of a particle, with the additional detail that they can be phase-shifted according to understanding today, which means that they seem to conserve a two-component number – i.e. a complex number.

What the uncertainty principle seems to state, is that the precision with which the position of a particle can be known, is inversely proportional to the precision with which its momentum-vector can be known, and vice-versa.

Photons are understood to have momentum vectors, even though when the photon-energy is low, such as for visible light, that momentum-vector also has low magnitudes. But the momentum-vector of a photon is supposed to follow entirely from the direction-vector it is traveling with, as well as being inversely proportional in magnitude, to its wavelength. The energy of the photon is also inversely proportional to its wavelength.

Because of the nature of the light output by a Laser, all the variables needed to know the momentum-vector of its photons are known – and are exactly equal. So the precision of their momentum-vectors is actually zero – i.e. their momentum vectors should have a variance of zero, based on the fact that they are parallel and fully monochromatic.

And so it would only seem to follow from the Uncertainty Principle, that the variance with which their position-vectors should be knowable, should be off-the-scale. By that logic, the position-vector of any one photon in the beam, cannot be knowable.

And so we seem to obtain a beam of light, only the wave-nature of which is knowable.

Dirk