Quantum Physics  Spooky Action in Scientific American of December 2018
This document contains comments about the article Spooky Action by Ronald Hanson and Krister Shalm In Scientific American of December 2018.
Recent experiments quash the hope that the unsettling phenomenon of quantum entanglement can be explained away.
Reflection
"Introduction"
page 52

The issue was wether particles separated by fast distances could retain a connection so that measurements performed on one affect the other.

What is missing is the word "faster than the speed of light" or instantaneous.
If that is added the word "fast" can de removed.
Also the word measurement requires an explanation. Why not use the word "any change" ?
See also Reflection 1  Clasical versus Quantum. What the reflection chalenges is that measurements

But under quantum theorie it happens all the time.

The issue is: is there such a physical influence?

Through his equation, Bell proposed a way to determine whether the universe could actual be that strange.

Physical phenomena are never 'strange', You can demonstrate physical phenomena by performing experiments.
See also Reflection 2  Bells equation..




Hidden variables



We might think that flipping a coin is equally random, but if we knew precisly the mass of the coin, how much force was used to flip it and all the details about the air currents hitting it, we would be able to predict exactly how the coin would land.

That is all in theory, in a thought experiment, in reality it is not true.

Even if we had perfect knowledge about all the properties of the electron and its spin before its passes through the magnetic field, quantum fuzziness prevents us from knowing which way it will go.

Quantum fuzziness is here introduced as an adhoc as an explanation that it is difficult to measure the properties of elementary particles. That is 'wrong'

(We can, however, calculate the probability of it going up or down).

Such a calculation requires a model. The question is what is that model.
IMO the model is that the spin can have every direction in space, without any preference. Using such a model the probality to measure that the spin is up in any direction is 50%.
I wrote this comment before reading the next sentence.

When scientist actual measure a quantum system, though, all these possibilities cease to exist somehow, and a single outcome is decided  the electron ends up having a spin that is oriented either up or down.

The logical sequence of steps followed seems strange. You start by performing certain experiments (plural) involving elementary particles which results are all (more or less) the same. For example you perform experiments which release two electrons, you measure the spin and there is no correlation. As I say you try different reactions. Sometimes, by pure accident, you try something different, you measure the spins and they are correlated. You repeat the experiment and the result is the same. Now comes the question: What is the cause of this correlation.
The point is that in this whole process no mathematics is involved.

some of its founding members, such as Albert Einstein and ERwin Schrödinger, felt uncomfortable with the fuzziness of quantum states.

It is very important to know how Albert Einstein's understand this concept of fuzziness. Which specific experiments that demonstrated fuzziness was he aware of?

Perhaps, they thought etc.

Why 'perhaps'? why not be more specific.


page 53

Surely any cat is either dead or alive and not in an absurd limbo in between, Schrödinger reasoned and therefore we should question the notion that atoms can be fuzzy at all.

The text seams to abandon the concept of superposition. That is remarkable.



Einstein with his collaborators took the argument a step further by analyzing two entangled electrons that are far apart.




Such correlations are certainly surprising when electrons are far enough apart that is impossible for them to communicate at the speed of light before their individual spins are measured.

Why are such correlations surprising? They are only surprising the first time when they are experimentally demonstrated.

How does the second particle know that the first one was up?

See also: Reflection 3  In search of Schrödinger's cat
Neither particle knows anything about the other particle. The secrecy about there behaviour lies in the way how they are created. If the particles are stable, the correlation between the two will be maintained over large distances.



Because of the perfect anticorrelation, she immediatly knows what the outcome will be if Bob measures his electron spin along z as well.

How does Alice knows that there is perfect anticorrelation? Only if she performs the experiment 1000 times.










Bell's Twist












These differences arise because the hidden variables cannot influence one another faster than the speed of light and therefore are limited in how they can coordinate their efforts.

This is the general in (classical physics): All physical influences are limited by the speed of light.

In contrast, quantum mechanics allows the two electrons'spin to exist jointly in a single entangled fuzzy state that can stretch over fast distances.

The question is what do you exactly mean by that and how do you know that.
The word entangled implies that there is a physical link between the different parts that are entangled, that are intertwined. You know that by performing experiments. The experiments performed on both parts demonstrate some sort of correlation.
The question now becomes: is this correlation a result of the experiments or was this correlation already there before the measurement.

Entanglement causes quantum theory to predict correlations that are up to 40 procent.

Chemical reactions can result in the creation of all sorts of elementary particles, including multiple electrons. The whole isue is that in some chemical reactions the spins of these electrons are correlated and in others not. When these electrons are correlated we call them entangled. IMO that is all.
In short the hidden variables are embedded in the chemical reaction.





The experiments have found correlations that violate Bell's inequality and seemingly cannot be explained by local hidden variable theories.

That maybe is true. But what is then the explanation for the results of these experiments?


page 54

In virtual all such experiments in the 20th century, scientists generated entangled photons at a source and sent them to measurements stations (standing in for Alice and Bob)

How do you know beforehand that this are entangled photons?
IMO by performing 1000 experiments.
(I think it is more logical to remove the word entangled)

The scientists then calculated the average correlations between the two stations outcome and plunged those into Bell's equation to check whether the results violated the inequality.

I think that the scientists first calculated the average results of each of the two stations. For the equation used see: Reflection 2  Bells equation..











Closing all the loopholes
page 54





According to quantum mechanics a particle can be in two states at the same time.

How do you know that a particle is in two states at the same time?

For example a quantum apple may not be red or yellow but a superposition of both?

How do you know (and when) that a quantum apple is in a superposition of both?

Particles can even be entangled with one another. That is if you look at one apple and find it red, the other instantly becomes yellow.

That means you look at the red apple first.
And what happens if you had looked at the yellow apple first?
The easiest solution is that both apples already have there real color before you look.
See also: Reflection 4  A preposterous experiment



Electrons have a spin: Up, Down, Or in a superposition both up and down.

How do you know that a spin is 'both up and down' and not Up and not Down? I think that that is tricky and requires a more elaborate explanation.

When the photons meet, they become entangled. By extension their distant respective electrons  which are easier to detect and measure than photons  also become entangled.

This is the most important part of the experiment.
What does it exactly physical mean: When the photons meet, they become entangled?
Each photon is correlated with its own electron. That means the photon is correlated with the direction of the spin of the electron in space. But the two photons are not correlated nor the two electrons.
In principle the photons when they meet they can interfere with each other (can become entangled) but such interference can have no influence on the state of the two photons. But this entanglement should always be the case. If this entanglement is rare than when it does the state of the two electrons was also rare implying that they were already in some sense correlated before the two photons actual met.





Although the photon loss related to the large separation in our case does not limit the quality of the entanglement, it does severly restrict the rate at which we can conduct Bell trails  just a few per hour.

In reality what you should do is to monitor, measure and report each occurence.
For example you should perform a trial run of 100 pairs when both photons are detected but are prevented to interfer i.e become entangled, versus a trial of 100 pairs which can interfer i.e are entangled. In the first run the electrons should not be correlated i.e. entangled and in the second run they should be correlated i.e. entangled.
Personally I doubt if they will.

etc. we found Bell's inequality was violated by as much as 20% in full agreement with the predictions of quantum theory.

It is much more important to know what happens with the correlations of the two electrons in the case when the photons are not allowed to interfer with each other versus when the are allowed to interfer.





Tests with cavaets


We entangled the spins of two electrons contained inside a diamond, in a space called a defect center, where a carbon atom should have been but was missing.

How do you know that the two electrons are entangeled i.e correlated ?

The two entangled electrons were in different laboratories across campus and to make sure no communication was possible we used a fast randomnumber generator to pick the direction of measurement.

This description is rather vaque and requires more details. Exactly how was this measurement performed in each laboratory? How do you know that each measurement does not change the corresponding electron?
When you read the whole paragraph this particular measurement is not the beginning of the whole experiment.



We achieved this separation by using a technique called entanglement swapping, in which we first entangle each electron with a photon.

A better description is as follows:

The whole experiment is performed in two laboratory 1280 m apart. In each laboratory there is a diamond. In each diamond is a defect center which acts as a trap for an electron. A laser is used to excite the electron which then emits a photon which is than entangled (correlated) with the spin of the electron.
This raises the issue how do you know that the photon is correlated with the spin of the electron.
What is also important is that at that moment of emission the two photons are not correlated. correct?

If we detect the photons on different sides of the mirror, the spins of the electrons entangled with each photon become entangled themselves.

 Again: How do you know this .?
 What happens if you detect the photons on the same side ?
 What causes this behaviour ?
These are important questions and not raised in the article.

In other words the entanglement between the electrons and the photons is transfered to the two electrons.

That has to be measured. See also Reflection 5  The Delft Experiment



























Closing the Loopholes


















Harnessing Entanglement


















Reflection 1  Clasical versus Quantum
Extraordinary processes require extraordinary explanation.
Einstein is a supporter of the two concepts: realism and locality. I expect Newton would agree with him.
The expectation of realism is described with this classical experiment:
 If you place a mouse in a cage in each of two rooms the behaviour of both mouses will be the same.
 If you place a cat near cage 1 only the behaviour of the mouse in cage 1 will change
 The behaviour of the mouse in cage 2 will only change if there is communication possible between the two mouses.
This behaviour change does not travel faster than the speed of light.
Quantum Mechanical experiments in general are like this.
 There is a specific chemical reaction which creates two electrons.
 From both electrons the spin is measured at A and B. The result is that one spin is up and the other spin one down.
 This experiment is repeated 1000 times with the result that in allmost each single case only one spin is up and one spin is down. That means never both up or both down.
 When you investigate side A than in 50% the spin is up and in 50% the spin is down.
 All of this means the correlation between the outcome (both spins) is 1.
What is als important when you increase the difference between A and the source or with both A and B this has no influence
on the outcome.
What is the most logical explanation that the spin is immediatly established during/directafter the chemical reaction.
Secondly that the measurement itself has no influence on the spin just before the measurement. The measurement itself can influence the state of the spin. That means you cannot measure the spin of the same electron twice. In fact the whole process between chemical reaction and measurement has to be investigated with great care because 'any' outside influence can in influence the state of the spin.
This explanation does not involve faster than light communication, nor spooky action at a distance.
To call the outcome of the quantum experiment a negative correlation is a better name than entanglement. Entanglement gives the impression that there is some sort of phyiscal link between the two electrons, That is not the case.
To call the electrons in a superposition state before the measurement is not wise. The point is that before the measurement the state is either up or down. The measurement itself will establish which is which, but is not itself the cause of the outcome. (Both measurement each will establish which is which, but are not itself the cause of the outcome.)
Reflection 2  Bells equation.
To understand Bells equation we use three coins: A,B and C.
When coin A is head up we call that state A. When coin A is tail up we call that state a. The chance if throwing state A is 50%.
When we use the two coins A and B the chance of throwing AB is 25%. When we use all the three coins the chance is the same.
When we use the three coins the chance of throwing BC is 25% and the chance of throwing AC is 25%.
In a different notation N(AB) < N(BC) + N(AC). (#1)
This is the Bell inequality using classical physics. This law states that the total number of AB pairs thrown is less than the number of BC pairs + AC pairs.
Quantum theorie predicts otherwise: under certain circumstances N(AB) > N(BC) + N(AC). (#2)
The real difference between equation 1 and equation 2 is the type of processes under consideration. Equation 1 describes the correlations between three coins. This is classical 'space'. Equation 2 describes the behaviour of the correlations between electrons (i.e qm space) created under special conditions (i.e. specific reactions). In that sense you are comparing apples with pears.
The question to ask how are the combined parameters AB, BC, AC calculated.
In the classical 'space' there are three similar equations (#1)
i.e. #1a) N(AB) < N(BC) + N(AC), #1b) N(BC) < N(AB) + N(AC) and #1c) N(AC) < N(AB) + N(BC).
All 3 equations are correct because N(AB) = N(BC) = N(AC) = 1/4. This is in accordance with 1/4 < 1/4 + 1/4
In the qm 'space' there are three similar equations (#2)
i.e. #2a) N(AB) > N(BC) + N(AC), #2b) N(BC) > N(AB) + N(AC) and #2c) N(AC) > N(AB) + N(BC).
when you combine the three you get: N(AB) > N(AB) + N(AC) + N(AB) + N(BC).
This equation can not be true (except when all values are zero). That means the three equations #2 can not all be valid for the same chemical reaction. IMO only one can be valid i.e the 3 equations are very direction sensitive.
This is a very serious objection.
Reflection 3  In search of Schrödinger's cat.
In the book "In search of Schrödingers cat" by John Gribbin
 at page 182 we can read:
Imagine two particles, that interact with one another and then fly apart, not interacting with anything else at all until the experimenter decides to investigate one of them. Each particle has its own momemtum, each is located at some position in space. etc. When much later, we decide to measure the momentum of one of the particles we know, automatically, what the momentum of the other one must be, because the total must be unchanged.
 at page 216 we can read:
Bohm's variation on the EPR argument starts out with a pair of proton's associated with one another in a configuration called the singlet state. The total angular momentum of such a pair of protons is always zero, and we can then imagine the molecule splitting into its two component particle which depart in opposite directions.
 at page 217 we can read:
So what happens when we try to measure the spin of our two separating particles? etc. But taken together the two particles must have exactly equal and opposte spin. So the random fluctuations (*) in the spin of one particle must be matched by balancing, equal and opposite 'random' fluctuations (*) in the spin components of the other particle far away. As in the original EPR argument the particles are connected by action at a distance.
In this book the word entanglement is not used.
The whole issue boils down to the idea if the two particles are trully connected.
The word fluctuation seems to indicate that the spin of each travelling particle continues changes. I doubt if that is the case.
Reflection 4  A preposterous experiment.
Consider a chemical reaction which creates (among others markers) two specific particles.
There are two measurement stations. Each station is capable to test if the particle is an electron or a proton.
The result of the first experiment, which involve both stations, that one particle is an electron and the other particle is a proton.
When you perform the same experiment 1000 times the results are the same: in total 1000 electrons and 1000 protons are detected equally divided between the measurement station. Each indivudual station has measured approx. the same number of electrons and protons.
The tricky question to answer is: is there entanglement involved? Are the electron and proton entangled?
When entanglement means is there a correlation between the results. The answer is Yes.
When entanglement means is there e physical link between the two particles. The answer is No. The correlation is a direct result of the reaction that creates the two particles.
In this specific experiment, the reaction creates an electron and a proton. Exactly the same reasoning applies if the reaction creates an electron and a photon (The Delft Experiment) or two photons (with different polarization).
Reflection 5  The Delft Experiment.
Starting point in the Delft Experiment are two laboratories (A and B) a distance 1280 m apart. In both laboratories the same experiment is performed:
 Inside a diamond an electron is excited which emits a photon. The electron and the photon are entangled meaning that the spin of the electron and the polarization direction of the photon are 'identical' i.e. are correlated.
That means electron A and photon A are correlated. The same with electron B and photon B. electron A is not correlated with electron B nor photon A with photon B.
 Next the two photons A and B travel towards each where they meet and become entangled.
This implies that the polarization direction of each photon should change (in some sense)
 By extension the two electrons A and B also become entangled. (See the text at page 55).
This implies that the spin of the electron A and B (wich are 1280 m apart) also have to change to become correlated.
In short: the state of two individuals electrons changes because at a distance two photons meet and interfer which each other.
If that is true than that is a very remarkable experiment. I doubt this
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Created: 2 December 2018
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