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 … )

Continue reading Photon Polarization / Superposition of States

Quantum Superposition, Quantum Entanglement

There is some ambiguity, with how I see other sources defining “quantum superposition”. From what I can extract, If there is a quantity of particles, whose combined wave-function is of a mixed nature between two other wave-functions, and if single particles are thought to emerge from that quantity, it can happen that the state of each particle is unknown, with a probability function between the two, mixed states. In that case, the particle can be superposed, as if having properties belonging to both states.

I think that some public writing fails to distinguish between the quantum superposition, and a possible, simple mixing of the properties of particles, whose states may be distinct.

(Edited 02/21/2018 :

In any case, if a particle is superposed, then one category of phenomena which may follow, is that its state may be “witnessed”, at which point it is no longer superposed. But while its state is superposed, without collapsing this superposition, its superposed states can have an effect on whether it can be witnessed or not. Specifically, if the wave-functions of the two states cancel out, then the presence of the particle cannot be detected, and therefore, its state can also not be witnessed. )

(As of 02/21/2018 :

As a result of a recent experiment, I’m learning to modify my vocabulary to some extent. As I now have it, the collapse of superposition of states is not always possible. But, a state can nevertheless be witnessed as belonging to one out of two entangled photons, in which case it will either be equal or opposite, depending on the case, to the corresponding state of the other particle, of that entangled pair of particles.

Whether this state is defined by the superposition of a separate pair of states, may not be relevant, to whether it can be witnessed.

My experiment did not involve entanglement. But, I’m inferring ideas from it anyway, and this would be a hypothetical example:

  1. A type of entanglement is possible, that affects linear polarization.
  2. A type of entanglement is possible, that affects circular polarization.

Example (1) should lead to matching, while example (2) should lead to opposite states. More specifically, Example (1) should lead to an inversion along an arbitrary axis.

I should add a detail which most people already know:

  • When a particle is witnessed as having a defined state, that state also changes.

End of Edit, 02/21/2018. )

I think that some experiments with entangled particles have as their basis, to use such cancellation, to reduce the rate at which some particles are witnessed in one beam, in an attempt to communicate this event to a second beam, whose particles should be entangled with the particles of the first beam.

The only part of this that really interests me for the moment, is the fact that light could be plane-polarized, and that at the same time, its photons could be in some superposed state. If a Polarizing Mirror next tries to extract light from that beam, which is polarized perpendicularly to the original direction, then the wave-function of this sought direction would be zero – even if this is due to cancellation. And then, not only would the amplitude of the derived beam be zero, but the state of the particles in the original beam, would also not be witnessed.

This would be, because a polarizing mirror actually ‘does something’, when a photon has the selected combination of properties. In contrast, if the linear polarizer is a Gel-Block, it ‘does something’, when photons have the opposite of the selected combination of properties – it absorbs them. Thus, for a gel-block not to witness the particles, it needs to be oriented parallel to the direction of polarization of the original beam.

Dirk