A misconception that can exist, in Quantum Mechanics.

First of all, I need to admit that I did not study Quantum Mechanics. I did study Physics, however, and have had numerous discussions with people, who either:

  • Studied Quantum Mechanics independently, Or
  • Studied Quantum Mechanics formally.

And those discussions have made me aware of a misconception that can exist, about how the wave-function of particles lead to measurement, but which will certainly not exist, for people who have studied the subject formally.

I have already made a posting, about The Myth Of Wave-Particle Duality, in which I highlighted what I see as an absurdity, in how the wave-function of particles is commonly defined. And, having written that, I should also point out, that the common sense which QM applies, not to treat Complex Eigenvalues as representing real properties of a particle, fails to spill over, to Complex Probabilities.

Even though the wave function of certain particles can be taken to exist factually, attempts to measure it as belonging to one particle will cause it to collapse. However, the way some people may visualize it, would be, that the wave-function continues to exist, simply because the Universe seems to be filled with waves, that continue to exist. And this is an especially possible misinterpretation of QM when the particle in question is a photon, just because low-energy photons, that lead to long and obvious wavelengths – i.e., radio waves and light from lasers – are so commonplace.

What happens with these obvious waves is that, most of the time, a large number of photons contribute to those waves, in such a way that each photon is being absorbed, in order for the actual wave to have been measured. And, when the photon is absorbed, as I have written elsewhere, it has also been ‘witnessed’, so that it is no longer in a superposed state. And, because one photon has been absorbed, it has also ceased to exist.

Even the way photons ‘work’ changes drastically, when individual photons have been measured. Modern physics is capable of measuring individual photons. When this happens, the detection of one photon either took place or did not. This can also loosely be described as ‘a click’, in contrast with ‘a wavelike phenomenon’, even if a more sophisticated method has been used, than methods that produce audible clicks. And it continues to be true for the low-energy photons, of which there will typically be a greater number, as it was with high-energy photons, that Historical Technologies such as a Geiger Counter were able to detect. This digital existence of single photons, when measured as such, is universal.

I suppose that a valid question which the reader may next ask could be, ‘How would this apply to Quantum Computing, which factually performs computations, based on wave-functions?’ And, there are basically two types of answers which I can think of. The actual Quantum Computer is a tiny device, that can work with individual photons, But:

  • When Scientists measure the output of a Quantum Computer, they may be using a larger number of actual Quantum Computers, all performing exactly the same computation, but in such a way that the combined light intensity is high enough to be measured directly at any instant in time, Or
  • They may be amplifying the photon which one Quantum Computing core actually outputs, so that one output photon leads to a more macroscopic phenomenon, through which Scientists can read the result of a Quantum Computation, Or
  • The optics of a single Quantum Computing core can cause numerous photons to perform the same computation.

Either way, even though the state within the Quantum Computer was defined in terms of QBits, what gets measured as output, is no longer so. Therefore, the Quantum Algorithm needs to be programmed in such a way, that the ability either to measure a photon or not to, will still lead to a successful experiment.

What I do know additionally is, that if the photon output by a Quantum Computer has been amplified, let’s say by a laser-like device, any superposition of the wave-function of the original photon has been collapsed, because, when lasers are used as light amplifiers, they also witness the Quantum State of the initial photon. (:1) At that point, the Quantum Computation has definitely ended.


 

 

One of the more remarkable observations I seem to have made about QM is, that ordinary refraction or reflection of light, such as by metallic surfaces or glass, does not seem to witness the photons. Anecdotally, the reader may present himself to his washroom mirror in the morning, secure in the knowledge that the mirror did not witness what the reader sees.  ;-) This form of light can continue in some superposed state. The reason I’ve concluded this, is the large number of experiments which Scientists carry out, and then write about, and which still seem to succeed, in spite of the fact that the Scientist’s apparatus has refracted or reflected the light used.

Now, whether the Scientist actually noticed, that he was refracting or reflecting the light, is a separate question. I suppose that if the experiment failed, the next thing the Scientist will naturally do, is search for why…

Continue reading A misconception that can exist, in Quantum Mechanics.

Designing a Cir-Pol Sensitive to Left-Handed Light.

A concept which the reader may already be familiar with, is a Circular Polarizer, which first linearly polarizes light, and then renders the result circularly-polarized. But somebody might be interested, in creating a filter which is only sensitive to light circularly-polarized in one direction. Well, it turns out that this is as straightforward to achieve, as the first example, if we can assume that we have a birefringent layer, light with one known wavelength, and that we can adjust the thickness of the birefringent layer as needed.

cir-pol-inv_1-svg

 

cir-pol-inv_4

 

If we assume that light can first be linearly polarized, and then passed through the birefringent layer, whose extraordinary and ordinary axes are both at a 45⁰ angle to that of the original plane-polarization, then due to the higher refractive index of the extraordinary axis, its wave-function – i.e., dipole-moment – will become delayed with respect to that of the ordinary axis, until the former is phase-delayed by 90⁰, which is also 1/4 the wavelength of the light, with respect to the latter. In the example shown above, left-handed, circularly-polarized light has been achieved.

But the question could next be asked, what would happen if, we passed this helical beam of light, whose dipole-moments propagate as a left-handed helix, through another birefringent layer, that exactly matches the previous one. And the result which we’d obtain, is that the phase-position of the wave-function along the extraordinary axis, which has already been phase-delayed 90⁰, will be phase-delayed again, by another 90⁰, so that now its phase-position will be at 180⁰ to that, along the ordinary axis. And so where the diagram above showed full amplitude, it will consistently show zero amplitude, and full amplitude will take place perpendicularly, to where it had been before.

Thus, by controlling in which direction the extraordinary layer is followed by the transmitting direction of the linear polarizer that comes next, we can control whether the combination will be sensitive to left-handed or right-handed light.

I suppose that the mental exercise can be taken one step further, and we can ask what would happen, if directly after circularly-polarized light was achieved, said beam was bounced off a metallic mirror, with the directions of propagation before and after, ‘normal’ to the surface of that mirror.

Continue reading Designing a Cir-Pol Sensitive to Left-Handed Light.

Hypothesis Disproved

A linear polarizer which I had ordered on-line recently arrived, and I did a promised experiment today, to test a hypothesis.

Hypothesis:

In This earlier posting and This earlier posting, I had proposed what amounts to two hypotheses combined:

  1. That photons may be circularly-polarized as one of their fundamental states, specifically left-handedly or right-handedly, so that other states of light can emerge from those states, eventually also due to a superposition of these two, intrinsic states.
  2. That quantum superposition can generally be collapsed, after which it will not resume as such, but after which witnessing of the resulting state may still take place.

The second hypothesis was meant as a synonym, for stating that:

  • Quantum-Mechanics is to take a form, in which certain states of particles are primary, while others are secondary, so that the secondary states can only form from the superposition of the primary states, while the reverse does not follow. This paraphrasing of the second hypothesis was further meant as a motivation to test, whether the particle-nature of matter and energy are in fact primary – hence, the circularly-polarized photons – and not the wave-nature.

Equipment used in the experiment:

A circular polarizer: A complex component, which has the logical operations of filtering light first, so that only light whose wave-function is plane-polarized along one axis is transmitted, and then secondly, to circularly-polarize the resulting light, so that its wave-functions along any two axes will be phase-shifted 90⁰ with respect to time. This was meant as a source for a primary state of light, polarized in an unknown direction out of two possible directions, since the retail store that sold me this circular polarizer, also did not label, whether it would produce left-handed or right-handed light. It’s to serve as a sufficiently-reliable source of circularly-polarized light.

A linear polarizer: A technically simpler component, which simply transmits light whose wave-function is plane-polarized along one axis, while absorbing light, whose wave-function is perpendicular to the plane transmitted. This was meant as an alternative, secondary state of light, formed as the superposition of left-handed and right-handed, circularly-polarized light.

A light-source: To consist of a mundane room-lighting fixture, which is assumed to generate randomly-polarized light.

Comments:

  1. The matter will be regarded as trivial, that when stating ‘the wave function’, I am referring to ‘the electrostatic wave-function’, which is assumed to be perpendicular to the magnetic wave-function, while also being in-phase with it at all times.
  2. The question will be ignored, whether the circular polarizer itself physically consists of two distinct layers, that perform its logical operations one-by-one, or whether it is of some other design, that accomplishes the same logical operations in some other way.

Procedure:

Control:

Light from the light-source will first be passed through the linear polarizer, and then through the circular polarizer, to confirm that two axes of plane-polarized light, when perpendicular, will lead to near-zero overall transmission, while when they are parallel, will lead to maximum transmission, which will also be used as the notional reference, corresponding to ‘50% transmission’.

Test-Case:

Light from the light-source will first be passed through the circular polarizer, the output of which is somehow to correspond to photons polarized in one circular direction, after which it will be passed to the linear polarizer.

Expected Result:

Because according to the hypotheses, the circularly-polarized light corresponds to an intrinsic state, which will no longer become superposed with the opposite state, the second component, the linear polarizer in the test-case, should not be able to output linearly- or plane-polarized light, because to do so should require the availability of both left- and right-handed photons. But, the linear polarizer will only receive a full amplitude of one or the other.

Real results:

Control:

The control case performed as expected.

Test-Case:

In the test-case, regardless of what orientation was chosen between the two polarizers, light emerged from the last, with constant brightness corresponding to ‘50% transmission’.

Conclusion:

While the principal is to be upheld, that circularly-polarized light may be one system for stating polarization, out of which plane-polarized light can emerge, eventually through quantum superposition, the reverse also seems to be possible.

However, this does not seem to favor an intrinsic state, as belonging to classical concepts of a particle, because the wave-function can be manipulated, regardless of the eventual existence of particles. And so this result further seems to suggest that wave-particle duality is plausible.

(Further Observations as of 02/24/2018 : )

Continue reading Hypothesis Disproved

How two subjects might be confused, that both have to do with polarized light.

There exists a concept, by which a single photon is visualized as having an electrostatic dipole-moment, which does not lie in a plane, but which performs a corkscrew, either left-handedly, or right-handedly, to start the phenomenon of electromagnetic radiation as based on circularly-polarized light, as opposed to being based primarily on plane-polarization. A quantity of photons could then still form plane-polarized light, not because they interact with each other, but because they coincide with each other in such a way, that their electrostatic fields cancel along one axis, but reinforce perpendicularly to the axis along which they cancel.

In reality, it’s dangerous to make such statements, about what exactly one photon does, because nobody has ever ‘seen’ a photon. We’re mainly able to make more-coarse measurements of what light does, when composed of swarms of photons, and must then deduce what the properties of one photon could be.

(Edit 02/20/2018 :

According to This Experiment, this hypothesis is disproved.

In the macroscopic world, circularly polarized light seems to exist, just as plane-polarized light does, without shedding much light on the subject of how one photon behaves, unless the latter subject is studied in much greater depth. )

But there is the matter of how any of this agrees with the classical, electrodynamic explanation of ‘light’, which would say that it has a magnetic dipole-moment, that oscillates with the same set of frequencies, with which the electrostatic dipole-moment, oscillates, but perpendicularly to the electrostatic moment.

The question could be asked of, If the electrostatic moment was plotted against time, What its phase-position would be, relative to the magnetic moment. And what I claim to know, is that they’d be in-phase.

This subject has been confused at times, with the question of whether the electrostatic component along one plane of polarization, is in-phase or out-of-phase, with the electrostatic component, along the perpendicular plane of polarization. Those are out-of-phase, in the case of circularly-polarized light, as well as in the case of circularly-polarized photons.

(Edit 02/07/2018 : )

 

photon_3

Now, the question about plotting this could get sidetracked, by the question of whether it’s more correct, if where the electrostatic dipole moment, which I’ll say is denoted by the Green line above, is pointing ‘upwards’, the magnetic dipole moment, which I’ll say is denoted by the Red line above, should be pointing ‘towards the viewer’, or ‘away from the viewer’. The way I presently have it, at the left end of the plot, the red line is towards the viewer at that instant. Because magnetic dipole moments differentiate between North and South, while electrostatic dipole moments differentiate between Positive and Negative, these signs of polarity are independent. By convention, the magnetic North pole is denoted by positive numbers. If it was assumed that the Red line corresponds to North, as shown above, then the photon would need to be traveling from the left, to the right, which also corresponds to an increasing parameter (t), just in case anybody is interested in actually analyzing the Math I entered.

(Edit 02/26/2018 :

This also implies that t does not correspond to Time. t us just a variable-name which often denotes a generic parameter. More-positive values of t will arrive on the right, before more-negative values do. )

In that case it should also be noted, that ‘Wolfram Mathematica’ switches the (Y) and (Z) plotting axes, so that (Z) actually faces upwards, but needs to be given as the 3rd input of a parametric 3D plot, while (Y) faces away from the viewer, which is different from how some other 3D plots work. The way I tend to visualize World Coordinates these days, (Y) should be facing Up, and (Z) should be facing Towards the Viewer.

(Updated 02/08/2018 … )

Continue reading How two subjects might be confused, that both have to do with polarized light.