Quantum Eraser 3.0

7/31/2019 Quantum Eraser 3.0

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Eugene Morrow Version 3.0 July 11, 2012 Contact: [email protected] Page 1 of 16

Quantum Eraser experimentA comparison of quantum mechanics (qm) and the Theory of Elementary

Waves (TEW)

Eugene Morrow Version 3.0 July 11, 2012 Contact: [email protected]

Contents

1 Introduction to the Quantum Eraser experiment.................................................... 2

2 How qm explains the Quantum Eraser experiment ................................................ 4Part 1.........................................................................................................................................4

Part 2.........................................................................................................................................4Parts 3 and 4..............................................................................................................................5Parts 5 to 8 ......................................................... ........................................................... ............6

3 Introduction to TEW .................................................................................................. 8Rule 1 Particle Follows Backwards .......................................................... ...............................8Rule 2 Self Interference ........................................................ ................................................... 9Rule 3 BBO Rule ........................................................ ........................................................... ..9Rule 4 Quarter-Wave Plate Rule....................... ........................................................... ..........10Rule 5 Linear Polarizer Rule....................................... ........................................................... 10

4 How TEW explains the Quantum Eraser experiment........................................... 11Basic setup of this experiment ......................................................... ....................................... 12Part 1.......................................................................................................................................12Part 2.......................................................................................................................................13Parts 3 and 4............................................................................................................................14Parts 5 to 8 ......................................................... ........................................................... ..........15

Summary........................................................................................................................16


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1 Introduction to the Quantum Eraser experiment

The original paper is published as follows:

S. P. Walborn, M. O. Terra Cunha, S. Padua, C. H. Monken, "Double-slit quantum eraser",

Physical Review A, Volume 65, 033818, Feb 2002.

A free copy of a PDF of this experiment is found as follows:

1. Go to http://en.wikipedia.org/wiki/Quantum_eraser_experiment

2. Under External links, look for The original paper on which this article is based.

The experimenters wrote the paper based on the quantum mechanics (qm) point of view. A new

theory the Theory of Elementary Waves (TEW) comes to very different conclusions about what

the experiment proves. We will look at the qm view of the experiment first, and then contrast this

to the TEW view. Both theories have questions on their explanations the main difference is that

the TEW explanation has nothing happening backwards in time.

The diagrams in this document were developed for displaying on debating forums where narrower

diagrams display better.

The experiment creates two entangled photons, and investigates how one entangled photon

appears to affect the other photon backwards in time.

The experiment starts with a basic setup to create two entangled photons. See the diagram below.

Figure 1: Basic setup of the Quantum Eraser experiment

An Argon laser at A creates a photon called Photon A of wavelength 351.1 nm, which is in the

ultraviolet part of the spectrum of light. Photon A bounces off a mirror at B to pass through a lens

at C which changes the photon in a way to assist results in this experiment. Photon A bounces off

a mirror at D to reach a crystal at E.

Located at E is a beta Barium Borate (BBO) crystal. This crystal splits Photon A into two photons:

Photon P and Photon S, each with a wavelength 702.2 nm (which is twice the incoming photon

wavelength). This new wavelength is in the red part of the spectrum of visible light.

Photons P and S have orthogonal polarizations which add up to the polarization of Photon A.

For qm, Photons P and S are entangled which means they are linked: a change to one will change

the other instantaneously (while the entanglement lasts).


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Photons P and S head towards detectors at P and S respectively. Both detectors consist of the

detector itself along with a bandwidth filter of 1nm and an 0.3 nm slit to help screen out random

photons not part of the experiment.

The two detectors at P and S are linked by a counter. When both detectors register a photon

arriving at the same time this implies we have detected the two entangled photons and so this is

counted in the experimental results. If only one detector registers a photon, then this is ignored.

Detector P never changes position and only verifies detection of an entangled pair of photons.

Detector S is mounted on a stepping motor and can be moved back and forth. After a consistent

length of time recording results in one location, Detector S moves to a new location to collect more

results. This is how Detector S can build a picture across a wide area.

The entanglement has two important benefits in this experiment. Firstly, the entanglement means

that if both detectors register a photon, then we know only one photon travelled from E to S. This

allows us to investigate one of the mysteries of the quantum world: how can a single photon create

an interference pattern with itself? Secondly, qm claims entanglement means a change to Photon P

changes Photon S. By making that change while Photon S is potentially interfering with itself, we

can further probe what is happening.Results are collected only when a photon arrives at both detectors together. What is important

about each result is the location of Detector S. How many photons does S collect in each position?

There are only two general shapes of results at Detector S either interference or no interference, as

shown below:

The pattern of the results tells us what is happening to a single photon: Photon S. The change

between the two results is what needs to be explained in this experiment. As we shall see, qm and

TEW have very different explanations for why we get the results.

The experiment has eight parts. In each part we make changes to the basic setup of the experiment,

and we collect results in each position of Detector S. In parts 1 to 4, the distance EP is 98 cm which

is shorter than the distance ES (125 cm). Parts 5 to 8 are the same as parts 1 to 4 except the distance

EP is 200 cm, so this is longer than ES (unchanged). When EP is longer than ES then the qm

explanation implies something is happening backwards in time.

In all eight parts Detector S finds either interference or no interference.


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2 How qm explains the Quantum Eraser experiment

The experiment has eight parts.

Part 1

A double slit is placed in the path of Photon S.

Figure 2: Part 1 from the qm point of view

The result is an interference pattern at S, caused by a single Photon S travelling through the double

slit at any time. How does qm explain one photon creating an interference pattern?

Photon S can reach E by two paths: ER1S or ER2S. For qm, it is important that we have no data

available on which path that Photon S chooses, so this means that Photon S can choose both paths at

the same time and interfere with itself. This is why qm believes that Detector S records an

interference pattern.

This raises some questions. Why does it matter to Photon S that which-path data is available?

The qm reason is purely mathematical an equation works. There is no discussion of what this

means in reality.

Part 2

The experiment changes so that which-path data is now available for Photon S. To do this, two

quarter-wave plates are inserted, one in front of each slit. The fast axes of the quarter-wave plates

are set to be orthogonal to each other.

Quarter-wave plates can change the polarization of beams of light passing through. The intention is

if Photon S has a particular linear polarization before the slit, then after the slit Photon is circular

polarized - clockwise in one slit and counter clockwise through the other.


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Figure 3: Part 2 from the qm point of view

The result is no interference pattern at S. We still have a single Photon S travelling through the

double slit at any time. Why do the quarter-wave plates stop Photon S from creating an interference

pattern?

For qm, the quarter-wave plates mean we can learn the which path data for Photon S by

measuring the polarization after the slits. For qm, once this which path data is available, Photon

S chooses only one slit and does not interfere with itself.

Notice that Detector S does not measure polarization, so we never learn the which path data. For

qm, this is not necessary what matters is that the data is available to be measured. The

experimenters write on page 033818-1 about the mathematics of this the which path data andconclude:

Therefore, it is enough that the which-path information is available to destroy interference.

This raises similar questions to Part 1. How is Photon S aware that which-path data is available?

Why does it matter to Photon S that which-path data is available? The qm reason is again purely

mathematical an equation works.

Parts 3 and 4

The experiment changes to erase the which-path data.

To do this, a linear polarizer is placed before Detector P. In Part 3, the polarizer is set to select thepolarization angle of Q1 the quarter-wave plate in front of slit R1. In Part 4, the polarizer is set to

select the polarization angle of Q2. Both of these parts are represented in the diagram below:


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Figure 4: Parts 3 and 4 from the qm point of view

The result is an interference pattern in both parts 3 and 4. Why does a change at L affect what is

happening between E and S?

The qm reason for this is that the which-path data was erased and so Photon S can now choose

both slits and interfere with itself once more.

What happened to the which-path data? When Photon P reaches detector P, then we learn the

new polarization of Photon P. Because of entanglement, qm claims this immediately makes Photon

S the orthogonal value of that polarization. Since we have changed the polarization of Photon S,

this overwrites or erases the polarization of Photon S after the slits. This means the which-

path data is no longer available.

The which-path data for Photon S is erased, and so Photon S chooses both paths and interferes

with itself. This is why qm believes that Detector S records an interference pattern again in Parts 3

and 4.

Once again, we have the same questions. How is Photon S aware that which-path data is not

available? Why does it matter to Photon S that which-path data is not available? The qm reason

is again purely mathematical an equation works.

Parts 5 to 8Parts 5 to 8 repeat Parts 1 to 4 respectively, with the distance EP longer than the distance ES. This

means we detect Photon P after Photon S no longer exists.

In Parts 5 to 8, the results are the same as for Parts 1 to 4 respectively and for qm, the same

explanations apply.


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Figure 5: Parts 7 and 8 from the qm point of view

This raises more new questions.

For qm in Parts 7 and 8, the moment that we detect Photon P is when the polarization of Photon S

changes to the new value, which erases the which-path data. How can Photon P affect Photon

S when Photon S no longer exists?

For qm, the explanation is called delayed erasure. Logically, it means qm claims that Photon P

affects Photon S backwards in time.

This logical conclusion does not appear to be a problem for the experimenters. On page 033818-5

they write:

We simply wish to show that the order of detection is not important, in concordance with the

literature.

On page 033818-6, they write: Our experimental data agree with the proposal of Scully, Englert,

and Walther that quantum erasure can be performed after the interfering particle has been detected.

As usual, the experimenters provide only mathematics to explain why this happens.

Many qm believers cite this experiment as proving that time can be reversed when necessary to

explain quantum results.Notice that in Parts 3, 4, 7 and 8, polarizer L and Detector P change what is happening on the

Detector S side of the equipment. This appears to be proof that Photon P communicates with

Photon S, and sometimes backwards in time. Supporters of qm might claim There is no other

explanation available.

That is no longer true. The next chapter gives a the basics TEW a rival theory to qm. Once the

basics are understood, the following chapter gives the TEW explanation of this experiment with no

communication between Photon P and Photon S and nothing happening backwards in time.


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3 Introduction to TEW

The account of TEW in this document has been prepared by myself (Eugene Morrow). The book

and paper on TEW do not over this experiment, so I cannot quote Dr. Little for this experiment.

Instead, I have applied the TEW principles to this experiment to create my own TEW treatment.

TEW has one aspect in common with qm they both have a quantum wave. TEW has the samequantum wave and assumes that it travels in the opposite direction to the particle. The quantum

waves are called elementary waves and are completely separate to the particles. Why assume this?

Because it makes TEW a local and deterministic theory.

The fastest way to understand how TEW explains the Quantum Eraser experiment, we need five

basic rules that we can apply.

Rule 1 Particle Follows Backwards

For TEW, a particle is always following an elementary wave in the reverse direction.

Figure 6: Rule 1 for elementary waves

A photon gets most of its attributes from the attributes of the elementary wave. For example, the

polarization and frequency of the photon come from the elementary wave.

Lets look at a simple example of a light globe shining light in a room. The walls of the room are

made up of masses, which emit elementary waves. The masses did not create the elementary waves

the waves existed already. When an elementary wave passes through a mass the mass leaves a

marker on the elementary wave that is unique.

Elementary waves are continuously being emitted by all masses in all directions, whether a particlecomes back or not. The elementary waves all carry the marker of that particular mass as well as a

particular polarization. One mass emits elementary waves of all polarizations linear, circular and

ellipsoid. There is hence a huge flux of elementary waves coming out of one mass.

Elementary waves sometimes reach a source of particles like a light globe. A source like a light

globe emits photons in response to the incoming elementary waves. The more intense the incoming

elementary wave the more likely that the source sends a particle back in response.

The particle (in this case a photon) travels back along the stream of elementary waves. Elementary

waves are not a wave in any medium. Elementary waves are flux that exist in all parts of space and

travel at c the speed of light.


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Rule 2 Self Interference

Normally, elementary waves from a mass called X will move away from each other. Sometimes,

elementary waves from X will change direction and end up meeting other elementary waves also

from X. The diagram below shows what happens.


There is interference when they have the same marker and the same polarization.

Notice how this rule is about self interference. Elementary waves with different markers (say X and

Y) are a separate issue. Often, waves with different markers will ignore each other, although there

are exceptions, and the next rule is about one such exception.

Rule 3 BBO Rule

BBO means a beta Barium Borate (BBO) crystal. A photon entering a BBO crystal can split into

two photons, which have orthogonal polarizations. How does the BBO crystal do this? Neither qm

or TEW knows how this is an experimental result. TEW focuses on the elementary waves that the

photons follow, as below:


From the TEW point of view, the BBO crystal is combining EWs. Later when a single photon is

returning along the BBO EW, that photon splits into two photons following the two incoming EWs.


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Rule 4 Quarter-Wave Plate Rule

A quarter-wave plate is an optical device that can change the polarization of light that is passing

through. As usual, TEW focuses on the elementary waves that the photons follow.


It is important to realise that in two special cases, the polarization Z2 is the same as Z1. For all the

other polarizations, Z2 is different to Z1.

Rule 5 Linear Polarizer Rule

The linear polarizer in this experiment ensures that photons have a certain linear polarization. For

TEW, this means looking at the elementary waves as below.


The next chapter gives the TEW explanation of the Quantum Eraser experiment.


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4 How TEW explains the Quantum Eraser experiment.

The book and paper on TEW do not over this experiment, so I cannot quote Dr. Little for this

experiment. Instead, I have applied the TEW principles to this experiment to create my own TEW

treatment.

The big difference is that the TEW explanation has no communication between Photon P andPhoton S and nothing happening backwards in time.

Note that the rules in Chapter 3 show how elementary waves behave in two types of double slit.

Figure 11: Elementary waves and two types of double slit

The Self Interference Rule is the deciding factor in the above two types. This experiment has

examples of both the above types.


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Basic setup of this experiment

Figure 12: Basic setup from the TEW point of view

As usual, the TEW diagrams show the elementary waves. Applying the Particle Follows

Backwards Rule, we know that photons travel in the reverse direction.

For TEW, elementary waves start from Detectors P and S. Both detectors emit elementary waves of

all polarizations, so there will be examples where a wave from P has the orthogonal polarization of

a wave from S. For these examples, the two waves combine into a single elementary wave that

travels from E to A.

The laser sends back Photon A which follows the elementary wave to E. At E, Photon A splits into

Photon P and Photon S which are following their respective EWs back to their detectors. Nothing

is communicated between Photon P and Photon S they are created together and from that point

onwards travel independently. As noted in the Chapter 3, TEW denies entanglement of Photon P

and Photon S.

However, TEW does agree with the use of the counter in this experiment. The counter will only

register a result for this experiment when both Photon P and Photon S arrive at the same time.

TEW agrees that this is a method to ensure that only one photon is travelling to Detector S at a time,

because Photon P and Photon S are always a pair of single photons.

We can now look at all 8 parts of the experiment from the TEW point of view.

Part 1

A double slit is placed in the path of Photon S.


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Figure 13: Part 1 from the TEW point of view

The result is an interference pattern at S, caused by a single Photon S travelling through the doubleslit at any time. How does TEW explain one photon creating an interference pattern?

Photon S is following the elementary waves from S to E. These waves pass a simple type of the

double slit, and so these elementary waves interfere at E. The usual photons get generated. Photon

S arrives in an interference pattern at S because the EWs from S are in an interference pattern at E.

There will always be questions about the TEW explanation, because questions can be asked about

all the rules.

For qm, the focus was on the lack of which-path data for Photon S. TEW claims that which-

path data is irrelevant it is the elementary waves that matter.

Part 2

The experiment changes so that which-path data is now available for Photon S. To do this, two

quarter-wave plates are inserted, one in front of each slit. The fast axes of the quarter-wave plates

are set to be orthogonal to each other.

Figure 14: Part2 from the TEW point of view


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The result is no interference pattern at S. We still have a single Photon S travelling through the

double slit at any time. Why do the quarter-wave plates stop Photon S from creating an interference

pattern?

Photon S is following the elementary waves from S to E. The quarter-wave plates create the

unique slits type of a double slit for most elementary waves. Photon S is in a steady stream for

most of the elementary waves they are following.

Elementary waves with two particular polarizations are an exception. As noted in the Quarter-

Wave Plate Rule, there are two special linear polarizations that will pass through both slits

unchanged, and hence create a simple type of the double slit.

The special linear polarizations are:

Fast axis for Q1 = the orthogonal direction to the fast axis for Q2.

Fast axis for Q2 = the orthogonal direction to the fast axis for Q1.

Note that these two special polarizations are pure there cannot be any mixture of the two.

These two polarizations do produce interference, but the interference is swamped by the steady

stream of photons for the unique slits types above. Look at the graph for Result no interferencegiven in Chapter 1. There is a slight hint of interference from these two special polarizations.

Once again, qm focuses on the availability of which-path data for Photon S. TEW uses the same

argument as before to reject this.

Parts 3 and 4

The experiment changes to erase the which-path data.

To do this, a linear polarizer is placed before Detector P. In Part 3, the polarizer is set to select the

polarization angle of Q1 the quarter-wave plate in front of slit R1. In Part 4, the polarizer is set to

select the polarization angle of Q2. Both of these parts are represented in the diagram below:

Figure 15: Parts 3 and 4 from the TEW point of view

The result is that Detector S get interference patterns in both parts 3 and 4. How does TEW explain

why L affects what is happening between E and S?


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The linear polarizer at L restricts the elementary waves to one of the two special polarizations

mentioned in Part 2. The BBO selects an elementary wave with the other special polarization. This

means a simple type of double slit for EWs going S to E, and interference.

This description may be too quick to take in. Lets describe it a bit slower:

1. The polarizer at L restricts the elementary waves going from P to E. The elementary

waves must have one of the special polarizations.2. At E, the BBO crystal selects a matching polarization, which is also one of the special

polarizations. This is because Q1 and Q2 are set to be orthogonal to each other, and the

BBO crystal selects polarizations that are orthogonal to each other.

3. When Photon P is created, it already knows what polarization it needs, because theelementary wave from P to E tells it. Photon P travels to P. As it passes L, nothing

special happens it already knows the polarization. Nothing is communicated

anywhere when it passes L or reaches P.

4. When Photon S is created, it is following the elementary waves from S to E. Becausethese waves are one of the special polarizations, they go through both slits and are in an

interference pattern. So Photon S arrives at S as part of an interference pattern. SoDetector S slowly builds up an interference pattern from lots of photons arriving, one by

one.

Notice how TEW claims there is no communication between the photons there doesnt need to be.

The elementary waves tell the photons what to do at all times, and the photons just follow their

waves as usual.

For qm, the focus is on how which-path data was erased by the linear polarizer at L by

entanglement. TEW rejects erasure and entanglement of the photons.

Parts 5 to 8

For TEW, it is already clear that the distances from E to P and E to S have no effect on the

elementary waves, so there is no change to the explanation and results.

In Parts 7 and 8, qm claims delayed erasure, meaning Photon P affects Photon S backwards in

time. For TEW, the photons do not affect each other the elementary waves decide everything.

All the qm claims about one photon affecting the other are completely unnecessary for TEW.


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Summary

Both qm and TEW have questions over their explanations.

For qm, the questions are about how Photon S knows if which-path data is available or not, and

possibly erased, and possibly erased backwards in time.

For TEW, the questions are about the basic rules of elementary waves.

The big difference between the two theories is that TEW is local and deterministic, and everything

happens in normal time.

For more on TEW, see:

The Theory of Elementary Waves by Dr. Lewis E. Little, 2009, ISBN 978-0-932750-84-6,

published by New Classics Library, Georgia, USA. See also www.elwave.org.

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