Entangled photon's

Experiment with Entangled photon's

Introduction

The understanding is, that one (each) photon vibrates (is polarised) in one particular flat plane. (Also called the plane of the Electric field).
Entangled photon's can be considered as a photon-pair with the property that the angle between the two planes (of each photon) is 90 degrees.
The behavior of the photon's is studied by means of experiments in different configurations. The experiment consists of one source, two counters and two filters.

          0 degrees                       0, 45 or 90
Counter1<--Filter1<---------Source--------->Filter2-->Counter2
Camara 1                                              Camara 2
                      Basic Configuration

The experiment consits of one source, which creates at each event two photons. One photon goes to the left and one photon goes to the right. Each photon is counted.
Before each counter is a filter. Filter 1 is always in the same position (0 degrees). Filter 2 can be in different positions (0, 45 and 90 degrees)
If the photon is counted depents on the filter angle and the plane of the photon as follows:

When the filter angle is 0 the photon is counted when the plane of the photon is between -45 and 45 degrees.
When the filter angle is 90 the photon is counted when the plane of the photon is between 45 and 135 degrees.
When the filter angle is alpha the photon is counted when the plane of the photon is between alpha-45 and alpha+45 degrees.

For a 3D sketch see:

The experiment is performed in 9 different configurations:

Source in the middle - Distance between Counter 1 and Counter 2 short - No filters
Same as 1 except with filters - Filter 1 angle 0 degrees Filter 2 angle 0 degrees
Same as 1 except with filters - Filter 1 angle 0 degrees Filter 2 angle 90 degrees
Source in the middle - Distance between Counter 1 and Counter 2 long - No filters
Same as 4 except with filters - Filter 1 angle 0 degrees Filter 2 angle 0 degrees
Same as 4 except with filters - Filter 1 angle 0 degrees Filter 2 angle 90 degrees
Source not in middle - Distance between Counter 1 and Counter 2 asymetric (one short on long) - No filters
Same as 7 except with filters - Filter 1 angle 0 degrees Filter 2 angle 0 degrees
Same as 7 except with filters - Filter 1 angle 0 degrees Filter 2 angle 90 degrees

Each experiment consists of 1000 events, that means 1000 photon pairs are created. The results are studied by means of two camera's
The distance short means for example 2m. The distance long 1000m.
This should be the only difference. If the short distance is done without fiber optics cables than the long distance should also be done without.
It is also possible to perform the test with fiber optics but than both the short and the long setup should contain fiber optics in all 9 configurations.

Questions:

Do you have practical experience with this experiment?
Are camera's usefull to study individual events?
What is the outcome of experiment 1
What is the outcome of experiment 2
What is the outcome of experiment 3
What is the outcome of the experiments 4-6
What is the outcome of the experiments 7-9
What is the relation between the Bell's inequality theorem and this experiment.
Do you expect that you can make a Quantum Computer based on the behaviour of these photons?
What is the relation between "The Schrodinger's Cat paradox" en the experiment discussed here.
Who was right Einstein (EPR) or Bohr (Copenhagen Interpretation)?

Purpose

The purpose of these questions and my answers is to test with a real experiment if my expectations and my understanding is correct.

Answer question 1 - Your practical involment

The purpose of these questions is to hear/learn from people with practical experience. That is very important, because only by performing actual experiments (compared with gedanken experiments) we can learn something.
I have no practical experience. My answers are based on what I expect that the outcome will be.

Answer question 2 - Are camera's usefull?

The purpose of the camera's is to compare the outcome of individual events. This is done by recording both counters continuous
My expectation is that with two camera's it should be possible to show that when there are no filters that at each event there actual are two photons. If this is not to be possible than the speed with which photon pairs are created should be adjusted.

Answer question 3 - Outcome experiment 1 - no filters

The purpose of experiment 1 is to calibrate this experiment. In order to do that we use a timer. At the start of the experiment the timer is reset. The experiment is stopped when the left counter reaches 1000. The timer is also stopped and the duration is recorded as t1.
The expectation is:

That the right counter also shows 1000.
That the 1000 counts observed by both camera's are all simultaneous and originate from 1000 events.

Left counter   1  2   3   4  5    6 7  8  9 10 11 12  13 14 .  .  . 1000
Right counter  1  2   3   4  5    6 7  8  9 10 11 12  13 14 .  .  . 1000
Timer pulses   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  n secs

The timer pulses are an indication that both counters are running simultaneous, but that the instances each at which those photon pairs are created, are random.

Answer question 4 - Outcome experiment 2 - Both filters 0 degrees

The difference between experiment 1 and 2 is that in experiment 2 two filters are used with the same angle ie 0 degrees.
At the start of the experiment the timer is reset. The experiment is stopped when the timer reaches t1.
The expectation is:

That the left and the right counter each show 500.
That the 1000 counts in total observed by both camera's are not simultaneous (and each originate from a different event)

Left counter   1  2  2   2  2   3   4  5  5  5   6 6  6  7  .  .  . 500
Right counter  0  0  1   2  3   3   3  3  4  5   5 6  7  7  .  .  . 500
Timer pulses   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  n secs

The above sketch shows that at each event only one counter increases.
There are a total of 1000 of those events in the same time period as in Experiment 1

Answer question 5 - Outcome experiment 3 - One filters 0 degrees, One Filter 90 degrees

The difference between experiment 2 and 3 is that the position of the right filter is moved from 0 to 90 degrees.
At the start of the experiment the timer is reset. The experiment is stopped when the timer reaches t1.
The expectation is:

That the left and the right counter each show 500.
That the 1000 counts in total observed by both camera's are all simultaneous (and each pair originate from the same event)

Left counter   1      2       3   4         5      6    7.  .  .  . 500
Right counter  1      2       3   4         5      6    7.  .  .  . 500
Timer pulses   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  n secs

The above sketch shows that at each event both counters simultaneous increase.
The above sketch shows that there are at least 500 events and that the frequency is much lower compared with Experiment 1
Because nothing at the source has changed we come to the conclusion that 500 events are missing. This are the photons polarised around 90 degrees (plus minus 45 degrees) for the left filter and around 0 degrees for the right filter.

Experiment 2 and 3 are very important. If the actual results are as predicted then they tell you that the only explanation is that the angle between the planes of both photons is 90 degrees. They do not tell you anything what the actual angles are.

You can also try a different angle. For example 45 degrees. The result will be something like this:

Left counter   1   1  2  3    3   4    5     5    6   7 7   8  .  . 500
Right counter  0   1  2  2    3   4    4     5    6   6 7   8  .  . 500
Timer pulses   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  n secs

If you observe the left counter than you should get in total 250 single events and 250 simultaneous events. For the right counter the result should be the same.
Those results are as expected based on the model that the difference between the polarisation planes is 90 degrees.
See Also Reflection Part 1

Answer question 6 - Outcome experiment 4-6 Long distance

The outcome in theorie should be the same as the first 3 experiments. However that is not what I expect. The reason is errors

In fact there are two reasons for errors:

How accurate are the filters? What happens towards the left filter (at 0 degrees) when there is a photon at exactly 45 degrees. Is this photon counted ?
If Not what happens with a photon at 44 degrees. It should be counted but maybe it is not.
If Yes what happens with a photon at 46 degrees. It should not be counted but maybe it is.
When a photon is at 22.5 degrees does the photon always moves in that same plane ? Even thousands of kilometers away ?

The outcome of the experiments 1-3 are influenced by the first type of error. Starting point in all those experiments is that the total number events is the same, as decided in experiment 1.

In experiment 2 it is possible that on either side 510 photons are counted with 10 photons detected simultaneous on both sides.
In experiment 3 it is for the same reason possible that on both side 510 are counted, all being simultaneous.

The outcome could also be different.

In experiment 2 it is possible that on either side only 490 photons are counted with 20 events missing.
In experiment 3 it is for the same reason possible that also on both side 490 are counted, all simultaneous, with 510 events missing.

In the experiments 1-3 the distance between the source and the filters is the same, but as short as possible. For exmple 2 meters.
The idea behind the experiments 4-6 is to perform the same experiments in order to test the second type of error. This is done by making the distance larger. For example 1000 m. My expectation is that the number of errors wil increase and is a function of distance.

Answer question 7 - Outcome experiment 7-9 Asymetric setup

The outcome again should be the same as the first 3 experiments
What we try to measure here is what is called "spooky action at a distance.". This is tested by performing the test in a assymetric fashion. For example the distance between the left filter and the source 2 meters and between the right filter 1000 meter.
As expected, within the margin of errors as discussed above, you will not find any difference. See also Reflection Part 2

Answer question 8 - Bell's theorem

For the Bell's inequality theorem for example see: Bell's theorem When you go there, there is also a section called: Practical experiments testing Bell's theorem where an experiment is described in order to demonstrate Bell's theorem.
Unfortunate no detailed information what exactly the theorem is, nor the details of the experiment.

When you compare the sketch of the "Bell" experiment with the experiment discussed in this document there are a lot of similarities.
In the "Bell" experiment they have a "coincidence monitor". In the experiment under discussion we use a camara. The function is more or less the "same" to decide if two counter counts (events) are simultaneous or not.
I leave the Bell's theorem for what ever it is worth. The outcome of the experiment under discussion IMO do not need those inequalities to prove something.

Answer question 9 - Quantum Computers

Very Unlikely.
Single Photons only can not be used as a basis to do any form of arithmatic primarily because you do not know which there polarisation angle is ie which state they are in.

Answer question 10 - Schrodinger's Cat Paradox.

Original the "Schrodinger's Cat Paradox" is a thought experiment and so is the experiment discussed here with the photon pairs.
IMO that is a not very scientific starting point. It implies risks.
When you study the Schrodinger's Cat Paradox your first impression is that it involves only one event. The cat is either alive or dead. In reality it is not because a radio active element is involved and to know the decay rate thousands of events are involved.
Suppose that the average decay time of the radio active element is 10 seconds. IMO it does not sound very scientific when you open the box after 10 seconds and that you claim just before that moment that the cat is in a superposition state of both being alive and dead. This while you know that there is a 50% chance that the cat is still alive when you repeat the experiment 1000 times.

Ofcourse you do not know what the outcome is of each a single experiment. It is the same as with the experiments with the photon pairs.
In the "Schrodinger cat experiment" there is one unknow parameter: the moment of the decay.
In single photon pairs experiments there are two unknown parameters: the moment of creation and the angle of the left photon.

Answer question 11 - Who was right Einstein or Bohr

You can only answer in the sense that A is right and B is wrong if their opinions are mutual exclusive. However than there stll is the possiblity that both are wrong
I doubt if their opinions are mutual exclusive. My impression is that the opinion of Einstein was more towards the outcome of one event, while the opinion of Bohr was more towards many events.
However there is one more player: John S. Bell, the inventor of Bell's Theorem. The question is can you use that theorem to decide who is right. My understanding of Bell's Theorem that it makes a prediction about a random process.
In simple wording: if the process is random than it is in agreement with the theorem. As such a process which partly contains correlations will not be in agreement. As such:

if you test only the left filter/counter outcome with Bell's inequality you will find that it is agreement, because the only thing you can test is absorbed versus not absorbed, and that pattern is completely random.
if you test boths sides/filters you will find a disagreement with Bell's inequality, because there exists a correlation between the polarisation angle of the two photons.

Does that anwer the original question about who is right? IMO No.
One thing is sure: The outcome of any induvidual experiment in which two photons are created can not be predicted in advance or in detail. For example we do not know the angles in which the photons moved either before or after they passed the filters. Quantum mechanics also does not describe this proces in detail. (It is even questionable if Quantum Mechanics predicts anything related to this experiment.)
In anyway, if the opinion of Einstein is that we do not know the reality in detail and that's Bohr opinion is the opposite than Einstein is right and Bohr is wrong. See also Reflection Part 4

Literature

The rules of quantum mechanics can be employed to predict the same experiment. I shall not give the details of how the prediction is derived etc
IMO this is a big omission specific if you want to prove that the "Bell inequality" is wrong and "Quantum mechanics" is right. In document 5.2 we read:: Without measuring B, we can now predict with certainty that B will be absorbed by a 0� polarized filter, because A and B always have opposite polarizations when measured in the same basis.
You do not know anything with certainty neither can you use the word always. The only things you know is by performing experiments. IMO the results of those experiments will tell you that do not know anything exactly, as such you can not say anything about B with 100% certainty. The reason are errors. For a discussion See: Answer question 6

Reflection Part 1. Experiment 1-3

The sole purpose of those 3 experiments is to demonstrate that what you create at the source are two photons which each is vibrating in one flat plan and that the angle between those planes is 90 degrees. What you do not know after each event is the actual angle of any of the two photon's

In case of experiment 2 you know for all individual events if the angle of the left photon is less than 45 degrees (counted left) or more than 45 degrees (and less than 125 degrees counted right)
In case of experiment 3 you know for 50% of all events that when there is a left

Reflection Part 2. Spooky action at a distance.

If you study the single events of the experiments 1-3 on their own than we know (assuming that we can record the state of the counters in slow motion) that at each event in the source there are 2 photons generated. We know that because each counter is updated simultaneous when there are no filters.
We also know that the angle between the plane of each photon 90 degrees is (with a certain error marge). We know that by using polarisation filters at different angles.
We do not know the actual angle of either photon in any single event.

Reflection Part 3

Because no signal can connect the two measurements if it travels at a velocity less than or equal to the speed of light, c, and because the choice of the direction of analysis can be made at the very last moment before measurement while the photons are in flight, how � argued Einstein � could one avoid the conclusion that each photon is carrying a property, determining the polarization outcome for any direction of analysis?
It should be better

if in stead of before measurement there should be written: before reaching the filters
it is very difficult to say anything about individual photon's in one particular instance (event)
if in stead of a property there should have been written: the property (namely that the angle between the plane of each photon is 90 degrees, established at the source)
However even without those "modifications" IMO Einstein is completely right, assuming that my predictions of the above experiments is correct
Does that mean that Quantum Mechanics is wrong (in this respect) ?
A little further we read:: The violation of Bell�s inequality, with strict relativistic separation between the chosen measurements, means that it is impossible to maintain the image �� la Einstein� where correlations are explained by common properties determined at the common source and subsequently carried along by each photon. We must conclude that an entangled EPR photon pair is a non-separable object; that is, it is impossible to assign individual local properties (local physical reality) to each photon. In some sense, both photons keep in contact through space and time.
I have no problem with the opinion of Albert Einstein.

The only thing it should be better if in stead of common property there should have been written:the property (namely that the angle between the plane of each photon is 90 degrees) The addition "established at the source" is not required.
On the other hand I agree that you cannot assign individual properties to each photon (Except that each moves in one particular plane).
I fully do not agree with the last sentence.

Reflection Part 4

So, EPR postulated that the existence of such "hidden variables", some currently unknown properties, of the systems should account for the discrepancy. Their claim was that QM theory is incomplete: it does not completely describe physical reality. System II knows all about System I long before the scientist measures any of the observables, thereby supposedly consigning the other noncommuting observables to obscurity. Furthermore, they claimed that the hidden variables would be local, so that no instantaneous action at a distance would be necessary. Niels Bohr, one of the founders of QM, held the opposite view that there were no hidden variables. (His interpretation is known as the "Copenhagen Interpretation" of QM.)
The problem is that there is no way to predict the actual outcome of the individual experiment exactly when filters are used like in the experiments 2 and 3. As such our knowledge is incomplete. You do not know what the pattern is at the left filter (0 degrees) and counter. See experiments 1, 2 and 3 The only thing you know, based on the setting of the filters, is that the angle between the planes of the photons is 90 degrees. To call those photon pairs entangled (or intertwined) is IMO a misnomer. To call them correlated is much better.

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Created: 15 May 2009

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