Five Popular Posts Of The Month

Tuesday, December 18, 2018

The Core Assumption of Every Known Single-Photon Experiment is Wrong.

The Core Assumption of Every Known Single-Photon Experiment is Wrong.
Dr. Valentin Voroshilov
DOI: 10.13140/RG.2.2.25910.96329

Recent paper (R. Chaves, G. Barreto Lemos, J. Pienaar; 2018) describes “statistics generated … by a photon in the Mach-Zehnder interferometer” in “the Wheeler’s delayed-choice experiment”, or its modified version.
In the original thought experiment (J. A. Wheeler, 1978), a photon enters an interferometer at the location of a beam splitter BS1, and “the experimenter chooses whether or not to remove the beam splitter BS2 after a photon has entered a Mach- Zehnder interferometer (at BS1).”
(Figure is used with the permission of the publisher)
The authors “treat the photon in the Mach-Zehnder interferometer as a two-level quantum system”. The statistics is to be supplied using “photon counting … detector(s)”.
The authors offer a quote (H. Paul, 1982) “It is essential that a single photon source is used, such that both detectors never click simultaneously. This guarantees that each photon cannot be modeled as a classical wave that is quantized only at the detector”.
The discussion essentially revolves around different possible descriptions of a photon traveling along only one possible path, or (as a manifestation of its wave-like properties) along two paths at the same time.
A beam splitter is a device an interaction with which may open for a photon two possible paths to travel along. For the original or a modified experiment, all versions of reasoning about possible outcomes of an experiment are based on the assumption that the photon that eventually enters a detector is always the same photon that entered an interferometer (e.g. at beam splitter BS1)

If that's not a case, the whole experiment loses all the sense.
This assumption, however, is wrong.
A beam splitter is a macroscopic optical device which consists of a large number of atoms or molecules.
When a photon is encountering a device, it does not interact with the device as a whole, it only interacts with a specific atom. As the result of that interaction the photon can be absorbed or scattered. In the latter case, the photon may encounter another atom, and interact with it. There is always non-zero probability that the original photon will be absorbed by the device, and a photon leaving the device will be produced by an atom in the device. Hence, in the latter case, the device does not open for a photon two different paths; a photon does not take one path or another, or both. An original photon gets absorbed, disappears. But, as the result of complicated interactions inside a device, the device eventually (the process takes time) emits a new photon, which on its way to a detector may encounter another optical device, etc. 

It's like two twine magician brothers showing a trick; one brother enters a booth and as soon as he closes the door another brother opens a door of a second boot and gets out. It looks like a man instantly moved from one booth into another one. In reality, those are two different men tricking everybody.
Exactly same situation will be happening when a photon interacts with any optical device, including (but not limited) a fully reflective mirror, a lens, a prism, a polarizer, a fiber optical cable.
Under these circumstance, any statement about the fate of the original photon entering a detector is wrong, because there is always non-zero, and not accounted for, probability that the photon entering a detector is not the original one, but the one emitted by an optical device (at least one of several devices existing between the very first device and a detector).
An optical device, any optical device, simply cannot be used to make a definite (known) alternation (from a set of possible alternations) in the behavior of a photon entering that device, because there is always non-zero probability of the photon being absorbed.
The result of an action of an optical device on light i.e. (reflection, refraction, polarization) is statistical, and based on the interactions between light in form of a wave (i.e. a large number of photons) and the charges in the device.
Without accounting for the exact interaction between a single photon and an optical device in its entirety, any statement regarding how an optical device may affect the behavior of a single photon is meaningless.
This realization negates all conclusions from all experiments (thought or actual) based on a “single photon – optical device” interaction (which are many).
1. Rafael Chaves, Gabriela Barreto Lemos, and Jacques Pienaar;  “Causal Modeling the Delayed-Choice Experiment”, Phys. Rev. Lett. 120, 190401 – Published 7 May 2018
2. J. A. Wheeler, in Mathematical Foundations of Quantum Theory, edited by R. Marlow (Academic Press, New York, 1978).
3. H. Paul, Photon antibunching, Rev. Mod. Phys. 54, 1061 (1982). 

Add-on from 12/24/2018
In “Cosmic Bell Test Using Random Measurement Settings from High-Redshift Quasars” (PHYSICAL REVIEW LETTERS 121, 080403 (2018))
The authors write: quote: “The entangled photon source … generated fiber-coupled photon pairs … in a state close to the maximally entangled Bell state. … Each photon was guided to a transmitting telescope (Tx) and distributed via free-space optical channels to the receiving stations of Alice and Bob. Each station consisted of a receiving telescope for entangled photons (Rx), a polarization analyzer (POL).”

The whole experiment and the following analysis of it is based on the assumption that the photons reaching the receiving stations are the same photons which had been initially generated.
But following the previous argument, there is non-zero – and not accounted for – probability that the originally generated photon (or photons) was (were) absorbed, hence the measured correlations between the photons registered by the receiving stations include correlations between different types of photons.
Quasar photons also have been in a contact with different materials which may have affected their properties, or absorbed and re-reemitted some of the photons.
The authors write, quote: “Within an optically linear medium, there does not exist any known physical process that can absorb and reradiate a given photon at a different wavelength along the same line of sight, without violating the local conservation of energy and momentum”
This statement demonstrates that the authors are aware of a possible absorption of some of the photons and the further replacement of those photons with new ones. They state as the fact that the new reradiated photons will the same wavelength as the absorbed photons. 
This fact is correct - ish.
This fact is correct - on average! - for a large number of photons, i.e. for an electromagnetic field traveling through a transparent medium. But I would like to see a proof of that fact/statement for a single photon colliding with a single electron in such a complex system as an atom. Plus, the authors ignore possible multi-photon events.
In the end, we need to assume that he process of absorption and reradiation may alternate the state of quantum coherence between different photons, and that option has not been considered among the ones which could, quote: “lead to corrupt choices of measurement settings within our experiment”.
However, when the goal of an experiment is to probe quantum correlations, the process which may alternate those correlations is the most important to be considered as a reason to corrupt an experiment.
In the end, the described experiment does not allow to established if the result describes solely the properties of entangled photons, or it describes the properties of a large system which was including entangled photons but also was affecting those photons in a non-accounted way.
The two specific examples reported in this piece demonstrate a very common situation when authors try to analyze the behavior of a microscopic system ignoring possible effects of the interaction between the system and the macroscopic measuring device (as the whole) beyond the effects the authors are looking for (beyond the possible states of the detectors). It is also a common case when authors apply properties of the interaction between a medium and a macroscopic number of microscopic particles to the interaction between a microscopic particle and a particle of the medium without having proved the possibility of this transition.
That proof should be based on the analysis of the evolution of a state-vector (wave-function) of a single photon (or two photons, to study the entanglement); the evolution is governed by a Hamiltonian; everything which may affect the photon (or photons) before it reaches a detector (before being measured, before wave-function gets "collapsed") must be a part of the
Hamiltonian; otherwise the theory does not describe the actual phenomenon.

Note: this post represents a formalization of one of the ideas discussed in my previous publications on the foundations of quantum mechanics, such as:
The Uncertainty Principle: a contemporary formulation.

Appendix I
 Your_manuscript LZK1101 Voroshilov
Re: LZK1101
    Comment on ``Causal modeling the delayed-choice experiment''
    by Valentin Voroshilov

Dear Dr. Voroshilov,
Your manuscript has been considered. We regret to inform you that we have concluded that it is not suitable for publication in any APS journal.

Yours sincerely,
Robert Garisto
Physical Review Letters

Celebrating 125 Years of the Physical Review   #PhysRev125

The rejection did not come as a surprise at all, I expected it.
But it demonstrates how APS operates.
This was not my first review, for example, check this link (at the end of the piece).
I also have been reviewing publications on physics education.
For example:

Decision on an article you reviewed: EJP-103392
Re: "Using Algebraic Reasoning to Model Gravitational Fields and Forces" by …

Thank you for your comments on this Paper being considered by European Journal of Physics. We wanted to let you know that we have now made a decision on this article based on all of the feedback received. On this occasion our decision is: Reject

If you would like to see the referee reports for this article, they are now available by viewing the decision letter for this article in your referee centre at .

We are very grateful for your assessment of this paper and we look forward to working with you again in the future.

Yours sincerely

On behalf of the IOP peer-review team:
Jessica Thorn - Editor
Dr Stephanie White – Associate Editor
Lucy Joy – Editorial Assistant

and Iain Trotter – Associate Publisher

IOP Publishing
Temple Circus, Temple Way, Bristol
Here are some examples of my reviewing practice (our of 13, so far):
As one can see, there is a difference between how APS reviewers operate, and how I operate as a reviewer.
When an author makes a claim, a reviewer has only six options to choose from.
1. The claim is wrong.
2. The claim is correct and significant.
3. The claim is correct and significant, but it has been already previously made, hence, not original.
4. The claim is correct but insignificant.
5. The claim is not clear, but may be correct and significant.
6. The claim is not clear, but even if will be correct, it will not be significant.
In any case, a reviewer can address the claim.
If that is not a case, it simply means a reviewer does not assess the claim, the reviewer assesses an author, and finds the author insignificant (does not deserve the reviewer’s time).
It is not a surprise to me that some reviewers may act in such a manner; they are people after all. The fact that they do science does not automatically mean that they also conduct a scientific behavior.
If someone can skillfully manipulate by a sophisticated machine which makes complicated parts for a space shuttle, would we call that one "an engineer"? Doubtful. The one does not design the parts, doe not have a big picture of how different parts should work together. the one is a technician. There are also many "scientific technicians". Someone who can skillfully apply a sophisticate algorithm to generate some new data. But the algorithm was developed by someone else. And the data mined in the process do not relieve anything truly unexpected. Such a person, though, can be a very good manager, skillful organizer, and make decisions about scientific importance based on how close the ideas are to his own.
This fact has already been described in literature, for example, in books like:
but especially, in 

Appendix II

I know why it is on hold. In this tiny paper, with no single equation, even no single number (can you imagine - no math!), I go right to the essence of a physical phenomenon (and as a very successful physics teacher, and more, I claim that that is the essence of physics). My claim affects numerous publications which use the evolution of a single photon (just Google "a single photon experiment") as the engine for arriving at final conclusions. The authors of those paper will have to find a fix (do math). 
That fix may be trivial. 
Or may not exist.
What I am curious about is who keeps it on hold?
New technologies allow reaching out to a wide audience bypassing established root. For example, in three says after the publication, this piece has reached 61 people.  
To this day (12/21/2018), my three blogs reached more than fifty thousand people (combined). I wonder, how many people have read the works of my reviewer?
 Appendix III
Yesterday (well, technically, already today), while I was falling asleep, it came to me!
Take a "classical" electron diffraction experiment. 
Everyone asks a question "How does an electron "know" where to hit a screen?" But the more interesting question is, "how does it "know" where NOT to hit a screen?" Restrictions on values of physical quantities is one of the most striking differences between quantum and classical mechanic. There are locations on a screen which will never be reached by an electron. But a screen is just a device which stops an electron and makes it seen where it was stopped. A screen can be moved closer or farther away (relative to a carbon crystal playing the role of a diffraction grating). That means that in the space beyond the carbon crystal there are lines, or surfaces where an electron can never be. Take a carbon crystal out, and an electron will be able to be at any location. Place a carbon crystal in, and the space changes, in the space beyond the carbon crystal there are locations where an electron can never be
A carbon crystal changes the space.
I imagine that changed space like a set of grooves with different deepness (in terms of epistemology, those grooves play role similar to Bohr's orbits). Those which have deeper troughs represent paths with a higher probability of an electron to travel. And the crests represent locations where an electrons cannot be (the Feynman's path for those lines/trajectories has zero amplitude). Of course, this picture implies that at any given instant an electron is located at a certain point in space, it is not smeared around all over space like a physical wave.
The motion of a particle heavier than an electron is not affected as mach as of an electron. A macroscopic particle does not "feel" any grooves at all.
By making a crystal larger and larger, by adding more and more atoms, grooves become more and more overlapping, and eventually, the space is "flattened".
But a crystal is made of atoms. The resulting change in space due to a crystal is the result of interposition (overlapping, interference - described by probability amplitudes (?)) of the changes in space due to an individual atom.
Atoms are made of particles.  
The resulting change in space due to an atom is the result of interposition (overlapping, interference) of the changes in space due to an individual particle.
Finally, we have reached the main point of this idea.
Every single particle changes space around it.
It is like in the Einstein's theory of general relativity.
An empty space is flat (I know, it is a space-time, and it may be disturbed by a gravitational wave, but as physics always does, we are starting from the simplest model).
If we place a heavy star in space, the space bends.
To see how it bends, we shoot light and observe its trajectory (does not have to be light, can be any object).
Now, on a microscopic level, we do the same.
An empty space is flat.
We place a particle in it, and space changes; we don't know yet - how it changes, but we know - it does. 
Each additional particle leads to an additional change.
To see that change we shoot a photon, or an electron, or another particle, which travels in a changed space.
That change may NOT be static (like bent but static space around a static star); in fact, most probably it is stochastic and leads to the existence of stable and unstable configurations (e.g. Bohr's energy levels). That change also may propagate faster than light ("spooky action over distance").
The mathematical description of this approach should lead to the Schrödinger's equation. 
Since we need to understand how a microscopic particle affects space, most probably we need to figure out how to quantize gravity.
For example, the metric tensor may represent only the average value of the space-time metric. The actual value of each component of the metric tensor stochastically fluctuates around the average one.Calculating averages or correlation factors implies using some other parameters as independent variables (at least one) - the meaning of those variables is not known (extra dimensions? spin? another actual field?). Placing a particle in an empty space changes the stochastic properties. The equations for the parameters describing stochastic properties of the space-time in the presence of particles may have stable solution for only specific values of some of the parameters (masses, charges). In a way, this approach is ideologically similar to the Einstein's (and others) approach to a united field theory, but now with an addition of a stochastic component to it. 

Killing The Schrodinger's Cat, at last and for good: part II

This post is one of the series of posts 
listed in Appendix below
Killing The Schrodinger's Cat, at last and for good: part II
After writing my first reflection on the first two chapter so the book (Part I), I continued reading the book and keeping my notes while reading.
In general, I enjoyed the reading, especially the parts about personal history of various people. In that part my expectation turned out to be correct, Adam Becker offers a good account of the history. 
Once in a while the reading initiated an argument, and those I present below.
Page 39
“When an electron is shot out into the tube, its wave function obeys the Schrödinger equation, undulating and propagating outward like a wave”
This statement makes us think that a wave function describes an actual physical field, like an electric field. This is simply wrong, because a wave function describes a number distribution ("an amplitude") in space and time (related to the probability distribution).
“So sometimes the electron behaves like a wave, and sometimes it behaves like a particle”.
This statement is wrong, because an electron never behaves like a wave and always behaves like a particle. However, that particle demonstrates different macroscopic behavior under the same macroscopic conditions – which is different from the behavior of macroscopic particles, those always demonstrate the same macroscopic behavior under the same macroscopic conditions. Specifically, an electron hits a screen at different locations. Electronspluralmany electrons under the same macroscopic conditions demonstrate behavior visually similar to the behavior demonstrated by a macroscopic waves. For example, when many electrons hit a screen at different locations, the resulting picture may look similar to the picture formed by waves traveling on a surface of water through two narrow slits. The difference between the waves in water and electrons is that every electron actually travel in space from a source to a screen, but water waves happen do to water molecules slowly moving about their equilibrium position and pushing on each other.
The whole idea of “wave-particle duality” was developed as an attempt to make sense of the theoretical concepts which could not fit into a well-developed classical picture. But since then physics has grown and today, almost hundred years later, we do not need to hold on this mental bridge anymore. At the dawn of the quantum mechanics the fact that a particle cannot demonstrate its location and velocity at the same time was a shock. Today, we just accept it as a fact; yes, a quantum object cannot demonstrate (note: I am not saying “have” – that is a different conversation about possible interpretations of quantum mechanics), so, a quantum object cannot demonstrate its location and velocity at the same time. The real “mystery” is why macroscopic objects, which are made of quantum objects, do demonstrate their location and velocity at the same time; how does that ability of the whole comes from an inability of its parts?
About a hundred years ago, when physicists would say something like “an incomplete description”, “incompatible variables”, “complementary”, they simply meant “different from classical”.
Page 59
“For any entangled system, Einstein’s choice applied: either the system is nonlocal, or quantum physics can’t fully describe all the features of that system”.
There is the third choice. The parts of a system interact via a physical interaction of some sort which has speed high enough to explain the behavior of the system – assuming the experiment is feasible at least in principle. The “high enough speed” condition may include interaction via agents which travel above the speed of light.
Page 100
“How do … the photons … know you’re watching them at all?” (in a double-slit experiment).
Answer – because “watching” means having photons interacting with  device which has one state in the absence of a photon and changes its state in the presence of a photon, and that inter-action changes the photon as well. Placing a detector by each slit makes the necessity for including those detectors in the mathematical description of the experiment.
The much more intriguing question is how does a photon “know” – after traveling through one of the slits (and we don’t know which) – where to hit a screen, or more importantly, where NOT to hit it? It seems like a photon “knows” that well before reaching a screen. A photon “knows” must mean that there is an interaction between a photon and the environment which affects its motion toward a screen. But the Schrödinger equation gives NO information about such interaction.
Here is where Bohm’s theory steps in.
Page 124
“Everett … insisted that a single universal wave function was aa there was”.
The idea of the existence of a single universal wave function for the whole existing universe is no different from the idea of a single universal Lagrangian for the whole world. It should be natural to every physicists who believes that our understanding of the universe should reflect the existence of the universe. However, the idea of the “many-worlds” logically is not connected with the idea of a single universal wave function; these two ideas do not demand each other.
Term “many-worlds” implies the existence of many different worlds – at the same time at the same place – (however one may see it). However, the passage (page 126) “universal wave function splits into more and more noninteracting parts” shows that those many worlds just represent different parts of the whole world, parts which exists at the same time at different locations. This picture is no different from any classical view on the world.
The notion that every single event in the universe creates new universes which correspond to all possible outcomes of the event, and an observer in each universe observes his own outcome may be seen as an innovation, but it has nothing to do with science, because does not help making predictions does not lead to new insights, and instead of making things easier and clearer, make them harder.
This is a situation when a treatment is worse than a disease.
Page 145
Bell’s quote “The great von Neuman … made assumptions in his proof that were entirely unwarranted”.
Many though experiments about entanglement make the same mistake. Human mind can imagine things which may seem natural, but physically “unwarranted”. It is not enough just to say “let’s assume these particles are entangled”, there has to be a specific physical mechanism in place for that to happen. If that specific mechanism of entanglement does not exist, the whole thought experiment makes no sense.
Page 149
“Bell used … Bohm’s version of EPR involving photons with entangled polarization. … When a photon hits a polarizer, it either passes through or gets blocked”
This is an example of a very commonly used interaction between a photon and an optical device (a polarizer, a mirror, a lens, etc.). And it is an example of a very common misunderstanding of the physical phenomenon happening during this interaction. Every author bases his/her logic on the options what may happen with a photon during this interaction, for example, a photon maybe be reflected, deflected, transmitted, blocked. And then the same photon keeps traveling (and something else is happening to it). The fact of the matter is that the photon traveling away from a device is simply not the same photon which was approaching a device. When a photon starts interacting with a device, it means it collides with an atom inside the device (at least one), it most probably gets absorbed, then – after some microscopic time interval – a new photon is emitted, which may be again absorbed, emitted, absorbed, emoted, etc., and such a process eventually leads to a photon – a new one! – leaving a device. Any conclusion on what property that final photon has is probabilistic and has to be derived based on quantum electrodynamics (in general). Until this description is provided, any conclusions on the results of an experiment involving a photon-device interaction may be plausible, but not necessarily definite.
A polarization axis (a transmission axis) of a polarizer is a macroscopic property of a device. When one photon encounters a polarizer, it encounter the existence of one atom or molecule. How would a photon “know” the direction of a transmission axis when it meets with only one atom? That atom absorbs a photon, emits a new one, etc. The final result is probabilistic. Hence, when a single photon interacts with a polarizer, there is always non-zero probability for a new photon be emitted by the polarizer on another side (what we call “passing through”). The phrase “a photon is polarized perpendicularly to the transmission axis” simply makes no sense. Hence, statement that (page 150) “the two [entangled] photons will always pass through together or be blocked together” is just wrong. Even if one polarizer completely absorbs one photon, there is a non-zero probability to see a photon on another side of a second polarizer. And that ruins the whole idea of the experiment, of any experiment with entangled photons (and also of the example with the casino).
Page 153
“That suggests a need for a radical revision of our conception of space and time, far beyond Einstein’s relativity”
Bell’s theorem may have pointed in that direction, but today “a need for a radical revision” is nothing but obvious, because, clearly, that seems the only way toward quantum gravitation – nothing else has been working.
Page 198
“further work on the subject would extinguish his academic career”.
The book provides many insights into the world of science, but it also provide many insights into the world of scientists. Those two worlds are not identical. The world of scientists is actually not much different from the world of actors, or politicians. “You are wrong” does not mean “you made a logical mistake here and there” (as it should be in the world of science), but “you think different from me, and that is wrong” (as it often in the world of scientists). And if you are not a member of “a pack”, you have a slim chance to find a good position.
Page 231
“What causes the collapse of the system-apparatus-environment combined wave function?”
The answer is – instability of immeasurable states (e.g. those states in a Hydrogen atom that would have energy NOT equal to the energy of the Bohr's energy levels).

It seems to me that many Western physicists think of a wave-function as of an actual real physical field, e.g. like electric field. Having this view naturally makes them wonder what happens to the field if just before a measurement it existed in a huge area of space but right after a measurement it exists only at a specific point. that is why they call it a "collapse" and trying to break their heads to understand what happened. However, a wave-function is not an actual physical field, but just a mathematical abstract - like the Dirac Delta-function. Yes, it does have strange behavior, but what is not strange about quantum world?
Page 245
“The idea that the universe as a whole was a suitable subject for scientific investigation was difficult for some physicists to swallow”.
A good example to demonstrate the difference between one who is paid for doing something in the field called “physics”, and a physicist (like not everyone who has a job title “a teacher” is actually a teacher).
Page 291
“But how can the photon “decide” whether to travel down just one path after it’s already passed through the first beam splitter?”
The answer is (again) – the photon does not need to “decide” anything. That photon disappears, being absorbed by the material of the beam splitter. Gone. The rest of the process does not include the original photon anymore.

Appendix I
After writing Part I, but before writing Part II, I also wrote two more piece on the matter, which provide some additional points of view, including on probability, entanglement, “many-words”, philosophy, a “delayed choice experiment”, and more:

I also have short pieces on a scientific method:

Three old pieces on physics:

Appendix II 
The mission (i.e. the reason for existence) of science as a human practice is making reliable predictions.
The mission of a scientists as an agent of that human practice is discovering the truth about the universe and representing it in a testable form (e.g. verifiable, or falsifiable).
When a faculty tells students "Quantum Mechanics is a complete theory, and it means this ..." he or she is simply lying - hence, he or she stops being a scientist. The truth (the fact) is that there are (exist, whether one likes it or not) different views on the state of Quantum Mechanics, and denying that fact is not a scientific action.
A mere fact that someone is involved in a scientific research does not automatically makes that one a scientists.

Appendix III
So many people and so much energy have been focused on a photon traveling through two slits, or two entangled photons or electrons, etc., so no one asks why waves on trillions of strongly interacting atoms behave in a way similar to the behavior of weekly interacting atoms in a dilute  gas? A macroscopic number of strongly interacting microscopic particles does not follow the laws of a macroscopic world. Instead, there is a trick, a recipe – called “quantization” – which works like a charm. Why?
The recipe works, what else do you need?