Entanglement Swapping and measurement vs. observation

[quantumfunction]

I think entanglement swapping shows the difference between measurement and observation. A measurement isn't as important as observation at least to subatomic particles.

Here's some key points

Two independent sources (labeled I and II) produce pairs photons such that their polarization states are entangled. One photon from I goes to Alice, while one photon from II is sent to Bob. The second photon from each source goes to Victor. (I'm not sure why the third party is named "Victor".)

Alice and Bob independently perform polarization measurements; no communication passes between them during the experiment—they set the orientation of their polarization filters without knowing what the other is doing.

At some time after Alice and Bob perform their measurements, Victor makes a choice (the "delayed choice" in the name). He either allows his two photons from I and II to travel on without doing anything, or he combines them so that their polarization states are entangled. A final measurement determines the polarization state of those two photons.

http://arstechnica.com/science/2012...cts-results-of-measurements-taken-beforehand/

Two things immediately jump out.

1. How do the particles know that Alice and Bob haven't made a choice to observe or share information?

2. Why do the particles correlate themselves with Victor's choice even after the fact?

The key point is Alice and Bob haven't made a choice to observe which measurement has occurred so the particles correlate themselves with Victor's observation.

Why doesn't measurement occur independent of Victor's choice?

I think conscious knowledge of the system is important on a fundamental level and we also see this in the delayed choice quantum eraser experiment.

A particle in that experiment at D0 behaves like a particle or an interference pattern based on whether information about it's entangled pair can be known or not after the particle has already hit D0.

Why does observation matter to subatomic particles?

When you look at entanglement swapping the particles are like Schrodinger's cat until Victor makes a choice even after Alice and Bob's particles have been measured. If Alice and Bob don't observe and share information about what measurement has occurred the particles going to Alice and Bob correlate themselves with Victor's observation.

Without a conscious observer knowing which state the particle will be in how could our universe exist? In other words, our universe formed because on a subatomic level they knew we would be here to observe there states like Victor.

 

[DrChinese]

I think entanglement swapping shows the difference between measurement and observation. A measurement isn't as important as observation at least to subatomic particles.

Here's some key points
http://arstechnica.com/science/2012...cts-results-of-measurements-taken-beforehand/

Two things immediately jump out.

1. How do the particles know that Alice and Bob haven't made a choice to observe or share information?

2. Why do the particles correlate themselves with Victor's choice even after the fact?

The key point is Alice and Bob haven't made a choice to observe which measurement has occurred so the particles correlate themselves with Victor's observation.

Why doesn't measurement occur independent of Victor's choice?

I think conscious knowledge of the system is important on a fundamental level and we also see this in the delayed choice quantum eraser experiment.

A particle in that experiment at D0 behaves like a particle or an interference pattern based on whether information about it's entangled pair can be known or not after the particle has already hit D0.

Why does observation matter to subatomic particles?

When you look at entanglement swapping the particles are like Schrodinger's cat until Victor makes a choice even after Alice and Bob's particles have been measured. If Alice and Bob don't observe and share information about what measurement has occurred the particles going to Alice and Bob correlate themselves with Victor's observation.

Without a conscious observer knowing which state the particle will be in how could our universe exist? In other words, our universe formed because on a subatomic level they knew we would be here to observe there states like Victor.

This is a complicated setup, and is certainly subject to the usual quantum interpretations.

1. They don't. In the delayed choice version, they are in fact already measured before their partners arrive at Victor.

2. The choices of Alice, Bob AND Victor are all part of the quantum "context". The ordering is irrelevant to the observed statistics, which depend on the overall context.

There is no known sense in which consciousness is relevant. That is pure speculation on your part at this point.

 

[quantumfunction]

This is a complicated setup, and is certainly subject to the usual quantum interpretations.

1. They don't. In the delayed choice version, they are in fact already measured before their partners arrive at Victor.

2. The choices of Alice, Bob AND Victor are all part of the quantum "context". The ordering is irrelevant to the observed statistics, which depend on the overall context.

1. Of course they do and this is one of the points of the whole set up. This is the reason you don't have Alice and Bob sharing information or knowing the outcome of their measurements until after Victor has made his choice to entangle/not entangle. How do the particles know that Alice and Bob haven't made the choice to share information about which measurement has occurred? The measurement with Alice and Bob should be independent of Victor's choice because Victor's choice occurs after the fact that Bob and Alice's particles have been measured.

2. Of course the ordering is irrelevant and that's the point! Observation is more important than measurement at least to particles who seem to correlate themselves based on observed/not observed. This places more importance on a conscious observer knowing which state the particle is in vs. the state being measured. When Alice and Bob make the choice to observe the state their particles are in that state will depend on Victor's future choice but when you break it down, past, present and future lose there meaning but observation doesn't.

 

[DrChinese]

1. Of course they do and this is one of the points of the whole set up. This is the reason you don't have Alice and Bob sharing information or knowing the outcome of their measurements until after Victor has made his choice to entangle/not entangle. How do the particles know that Alice and Bob haven't made the choice to share information about which measurement has occurred? The measurement with Alice and Bob should be independent of Victor's choice because Victor's choice occurs after the fact that Bob and Alice's particles have been measured.

2. Of course the ordering is irrelevant and that's the point! Observation is more important than measurement at least to particles who seem to correlate themselves based on observed/not observed. This places more importance on a conscious observer knowing which state the particle is in vs. the state being measured. When Alice and Bob make the choice to observe the state their particles are in that state will depend on Victor's future choice but when you break it down, past, present and future lose there meaning but observation doesn't.

1. We're talking about different things, it appears. Observers Alice and Bob can be well separated (outside each others' light cones) and the results do not vary. They can agree to what settings to use or not, that doesn't matter either.

2. The particles measured by Alice and Bob are correlated if Victor swaps entanglement via their partners. The key is that entanglement swapping can occur after Alice and Bob make their observations, and there is still correlation. Also:

a. It is impossible to comprehend what you mean as a difference between the words "observe" and "measure". They are normally used interchangeably on this forum.

b. There is no known sense in which the conscious mind plays a part in quantum mechanics.

 

[quantumfunction]

1. We're talking about different things, it appears. Observers Alice and Bob can be well separated (outside each others' light cones) and the results do not vary. They can agree to what settings to use or not, that doesn't matter either.

2. The particles measured by Alice and Bob are correlated if Victor swaps entanglement via their partners. The key is that entanglement swapping can occur after Alice and Bob make their observations, and there is still correlation. Also:

This is wrong and this goes to my point. Alice and Bob don't make observations until after Victor has made his choice. Like I said, this is key. If Alice and Bob made an observation before Victor's choice then Victor's choice wouldn't matter. This is because Alice and Bob's observation would already be part of their environment and there's nothing Victor can do to change what Bob and Alice observed. Here's more from the actual paper of the experiment.

In our experiment, the primary events are the polarization measurements of photons 1 and 4 by Alice and Bob. They keep their data sets for future evaluation. Each of these data sets by itself and their correlations are completely random and show no structure whatsoever. The other two photons (photons 2 and 3) are delayed until after Alice and Bob’s measurements, and sent to Victor for measurement. His measurement then decides the context and determines the interpretation of Alice and Bob’s data.

Bingo

Alice and Bob's data should be independent of Victor's choice. Why should it matter to the particles that went to Bob and Alice if Victor will choose to entangle/not entangle? The reason this matters is because Bob and Alice Don't observe their results. It goes onto say:

In the entanglement swapping 1-3 procedure, two pairs of entangled photons are produced, and one photon from each pair is sent to Victor. The two other photons from each pair are sent to Alice and Bob, respectively. If Victor projects his two photons onto an entangled state, Alice’s and Bob’s photons are entangled although they have never interacted or shared any common past. What might be considered as even more puzzling is Peres’ idea of “delayed-choice for entanglement swapping”4,5 . In this gedanken experiment, Victor is free to choose either to project his two photons onto an entangled state and thus project Alice’s and Bob’s photons onto an entangled state, or to measure them individually and then project Alice’s and Bob’s photons onto a separable state. If Alice and Bob measure their photons’ polarization states before Victor makes his choice and projects his two photons either onto an entangled state or onto a separable state, it implies that whether their two photons are entangled (showing quantum correlations) or separable (showing classical correlations) can be defined after they have been measured.

Alice and Bob's have been measured but not observed. There's no interaction between Alice and Bob's particles after they have been measured. This is why the future evaluation of Alice and Bob's particles of correlation/separable are determined by Victor's future choice. If measurement was the determing factor then Victor's choice would be meaningless.

 

[StevieTNZ]

There is an interesting article by Reinhold Bertlmann entitled "Time-ordering dependence of measurements in teleportation" (http://link.springer.com/article/10.1140/epjd/e2013-30647-y), and I quote from the first page of the article:

Entanglement swapping offers the possibility to an external observer, called Victor, who has access to a Hilbert space which is tensorized with an other Hilbert space, to change a quantum state in the other Hilbert space by performing a measurement in his space. The quantum state, which previously appears separable for Alice and Bob, but not pure, is changed into a new state that is now pure and entangled for Alice and Bob. This new (entangled) state is generated by a collapse of the quantum state. That is only possible for states where Victor is entangled with the total system of Alice and Bob.

However, if this entanglement with Victor gets destroyed by a measurement of Alice and/or Bob – as it is the case in the experiment of reference [1] – then also Victor, by performing a measurement, has no chance to deliver an entangled state to Alice and Bob. The correlations that remain can be explained by a mixed state with only classical correlations.

Reference [1] refers to the delayed-choice entanglement swapping experiment performed by Zeilinger et al., published in 2012.

 

[quantumfunction]

There is an interesting article by Reinhold Bertlmann entitled "Time-ordering dependence of measurements in teleportation" (http://link.springer.com/article/10.1140/epjd/e2013-30647-y), and I quote from the first page of the article:Reference [1] refers to the delayed-choice entanglement swapping experiment performed by Zeilinger et al., published in 2012.

Very good point.

This is exactly what I'm saying. If Alice and Bob's measurement is observed by Alice and Bob then Victor's choice is rendered meaningless to Alice and Bob.

I have always said if you had a hypothetical time machine you can change the past only if it hasn't been observed yet. So if hypothetical time travelers saw that Romney won the election while looking at our timeline, they can go back further in time to change the future and elect Obama as long as the event hasn't occurred and been observed yet by us.

This is similar because Alice and Bob's particles haven't been observed yet therefore Victor can collapse the quantum state and swap entanglement with his choice. He can't do this if Alice and Bob's particles communicate.

So it's like they're in one universe where they all exist together unless Alice and Bob's particles interact then Victor's particles will be classically separated from Alice and Bob's particles. It's like Alice and Bob's particles are in another universe.

 

[DrChinese]

This is wrong and this goes to my point. Alice and Bob don't make observations until after Victor has made his choice. Like I said, this is key. If Alice and Bob made an observation before Victor's choice then Victor's choice wouldn't matter. This is because Alice and Bob's observation would already be part of their environment and there's nothing Victor can do to change what Bob and Alice observed. Here's more from the actual paper of the experiment.

In our experiment, the primary events are the polarization measurements of photons 1 and 4 by Alice and Bob. They keep their data sets for future evaluation. Each of these data sets by itself and their correlations are completely random and show no structure whatsoever. The other two photons (photons 2 and 3) are delayed until after Alice and Bob’s measurements, and sent to Victor for measurement. His measurement then decides the context and determines the interpretation of Alice and Bob’s data.

Bingo

Alice and Bob's data should be independent of Victor's choice. Why should it matter to the particles that went to Bob and Alice if Victor will choose to entangle/not entangle? The reason this matters is because Bob and Alice Don't observe their results. It goes onto say:

In the entanglement swapping 1-3 procedure, two pairs of entangled photons are produced, and one photon from each pair is sent to Victor. The two other photons from each pair are sent to Alice and Bob, respectively. If Victor projects his two photons onto an entangled state, Alice’s and Bob’s photons are entangled although they have never interacted or shared any common past. What might be considered as even more puzzling is Peres’ idea of “delayed-choice for entanglement swapping”4,5 . In this gedanken experiment, Victor is free to choose either to project his two photons onto an entangled state and thus project Alice’s and Bob’s photons onto an entangled state, or to measure them individually and then project Alice’s and Bob’s photons onto a separable state. If Alice and Bob measure their photons’ polarization states before Victor makes his choice and projects his two photons either onto an entangled state or onto a separable state, it implies that whether their two photons are entangled (showing quantum correlations) or separable (showing classical correlations) can be defined after they have been measured.

Alice and Bob's have been measured but not observed. There's no interaction between Alice and Bob's particles after they have been measured. This is why the future evaluation of Alice and Bob's particles of correlation/separable are determined by Victor's future choice. If measurement was the determing factor then Victor's choice would be meaningless.

We are discussing several different ideas. We should probably get agreement on the setup, from your reference:

1. Two independent sources (labeled I and II) produce pairs photons such that their polarization states are entangled. One photon from I goes to Alice, while one photon from II is sent to Bob. The second photon from each source goes to Victor. (I'm not sure why the third party is named "Victor".)
2. Alice and Bob independently perform polarization measurements; no communication passes between them during the experiment—they set the orientation of their polarization filters without knowing what the other is doing.
3. At some time after Alice and Bob perform their measurements, Victor makes a choice (the "delayed choice" in the name). He either allows his two photons from I and II to travel on without doing anything, or he combines them so that their polarization states are entangled. A final measurement determines the polarization state of those two photons.

As I said, Alice and Bob measure before Victor. And they can be sufficiently separated so that their photons have never existed within a common light cone. Ergo they have no causal influence on one another, unless such is FTL. Of course, Alice and Bob DO observe their results. They are correlated if Victor later decides to entangle them. Otherwise, they are not correlated. This is the point of the experiment, that a correlation is made to occur after particles are already detected and the outcomes recorded/

I repeat that there is no meaning on this forum to any appreciable difference between the words observe and measure. Further, the existence of conscious observers is irrelevant as far as anyone knows. And there is no "other universe" (whatever you mean by that). They only relevant regions of spacetime in this setup are those defined by light cones from the 2 photons sources, labelled I and II.

 

[quantumfunction]

Of course, Alice and Bob DO observe their results.

If this is the case let's see the quote from the original paper.

The quantum state hasn't been observed if it was then Victor's decision wouldn't change anything.

Measurement and the observers knowledge of which measurement occurred are two different things. If there's no knowledge of what measurement occurred then Victor's choice can determine correlation/separable for Alice and Bob's particle.

Alice and Bob's local measurements are only independent of Victor's choice if Alice and Bob's particles interact.

Here's a quote from the original paper.

On the basis of Victor’s measurement settings and results, Alice and Bob can group their earlier and locally totally random results into subsets which each have a different meaning and interpretation. This formation of subsets is independent of the temporal order of the measurements. According to Wheeler, Bohr said: “No elementary phenomenon is a phenomenon until it is a registered phenomenon.”7,8 We would like to extend this by saying: “Some registered phenomena do not have a meaning unless they are put in relationship with other registered phenomena.

Exactly,

In other words local measurements are meaningless in isolation of the whole state.

Why isn't measurement of Alice and Bob's particle independent of Victor's choice? It's because the quantum state which includes particles 1,2,3 and 4 hasn't been observed until Victor makes a choice. If Alice and Bob's particles are observed and knowledge about each state is known, then Victor is blocked off from determining correlation/separable for Alice and Bob's particles.

This goes back to the question, how do Alice and Bob's particles know that they're part of a system that includes particles 1,2,3 and 4 or they're not? How do they know when Victor has entangled or not entangled?

When Victor doesn't entangle, particles 1&2 and particles 3&4 remain entangled. When Victor makes the choice to entangle, they lose their correlation and it's swapped.

WHY DOES VICTOR'S CHOICE HAVE ANY MEANING AFTER ALICE AND BOB'S PARTICLES HAVE BEEN MEASURED?

The 4 particles have to remain as a single state and the only thing that allows them to remain a single state is there's no communication or interaction between Alice and Bob.

 

[bhobba]

I repeat that there is no meaning on this forum to any appreciable difference between the words observe and measure. Further, the existence of conscious observers is irrelevant as far as anyone knows. And there is no "other universe" (whatever you mean by that). They only relevant regions of spacetime in this setup are those defined by light cones from the 2 photons sources, labelled I and II.

Nor is a distinction made in any textbook I am aware of - and I have read quite a few. Observation and measurement are basically synonymous. That said observation is a bad term we are stuck with for historical reasons. Observation in QM does not imply a conscious observer despite its usual day to day meaning.

Thanks
Bill

 

[bhobba]

WHY DOES VICTOR'S CHOICE HAVE ANY MEANING AFTER ALICE AND BOB'S PARTICLES HAVE BEEN MEASURED?

Choice has nothing to do with anything. It could be done by a machine - it makes no difference. This whole conciousness thing comes from a misinterpretation of what observe means in QM and some ideas from the early days of QM that are now very fringe. They are still about because they can't be disproved, but very few physicists ascribe to it.

Thanks
Bill

 

[zonde]

WHY DOES VICTOR'S CHOICE HAVE ANY MEANING AFTER ALICE AND BOB'S PARTICLES HAVE BEEN MEASURED?

You might be missing some details of experiment. Victor's choice does not matter. What matters is Victor's measurement. And based on result of Victor's measurement Alice and Bob's results are postselected in different subsets that show appropriate correlations.

 

[quantumfunction]

You might be missing some details of experiment. Victor's choice does not matter. What matters is Victor's measurement. And based on result of Victor's measurement Alice and Bob's results are postselected in different subsets that show appropriate correlations.

Of course Victor's choice matters. That's the delayed CHOICE portion of the experiment. Here's a quote directly from the experiment.

In the entanglement swapping1-3 procedure, two pairs of entangled photons are produced, and one photon from each pair is sent to Victor. The two other photons from each pair are sent to Alice and Bob, respectively. If Victor projects his two photons onto an entangled state, Alice’s and Bob’s photons are entangled although they have never interacted or shared any common past. What might be considered as even more puzzling is Peres’ idea of “delayed-choice for entanglement swapping”4,5 . In this gedanken experiment, Victor is free to choose either to project his two photons onto an entangled state and thus project Alice’s and Bob’s photons onto an entangled state, or to measure them individually and then project Alice’s and Bob’s photons onto a separable state. If Alice and Bob measure their photons’ polarization states before Victor makes his choice and projects his two photons either onto an entangled state or onto a separable state, it implies that whether their two photons are entangled (showing quantum correlations) or separable (showing classical correlations) can be defined after they have been measured.

Victor is free to choose.

Whether this choice is controlled by a quantum random number generator or a human brain, it's still a free choice. Victor's CHOICE matters and the experimenters explain why.

In order to experimentally realize Peres’ gedanken experiment, we place Victor’s choice and measurement in the time-like future of Alice’s and Bob’s measurements, providing a “delayed-choice” configuration in any and all reference frames. This is accomplished by (1) proper optical delays for Victor’s photons and (2) a high-speed tunable bipartite state analyzer, which (3) is controlled in real time by a quantum random number generator (QRNG)6 . Both delay and randomness are needed to avoid the possibility that the photon pairs can “know” in advance which setting will be implemented after they are registered and can behave accordingly by producing results of a definite entangled or a definite separable state. Whether Alice’s and Bob’s photons can be assigned an entangled state or a separable state depends on Victor’s later choice. In Peres’ words: “if we attempt to attribute an objective meaning to the quantum state of a single system, curious paradoxes appear: quantum 2 effects mimic not only instantaneous action-at-a-distance but also, as seen here, influence of future actions on past events, even after these events have been irrevocably recorded.”4

DEPENDS ON VICTOR'S LATER CHOICE.

Choice is very important and I would say CHOICE creates reality. Victor's CHOICE to entangle/not entangle created a reality in that environment.

If I go to the store to buy a bag of Funyuns or a bag of Doritos and I make the choice to buy Funyuns, I then go to the cooler to buy a drink I like with my funyuns, I bump into a High School friend, he invites me to a cookout, I go and meet his sister that's in town, we start dating, get married and have 2 kids.

My choice to buy funyuns created a reality and history in this environment. I could have made a choice to buy Doritos and went straight to the checkout and never bumped into my HS friend.

The point is, choice causes a measurement to occur and a history unfolds from that choice. We see the same thing with Victor. He makes a choice to entangle and a history unfolds where Alice and Bob's particles are entangled. He makes a choice not to entangle and a history unfolds where Alice and Bob's particles aren't correlated.

Choice is very important because Victor makes a choice after Alice and Bob's particles have been measured. He used a quantum random number generator so Victor's choice could be random and therefore Bob and Alice's particles couldn't "know" Victor's choice. So it comes down to the knowledge the observer has about Alice and Bob's particles. If Alice and Bob have no communication then their particles correlate themselves with Victor's choice.

 

[DirkMan]

Choice has nothing to do with anything. It could be done by a machine - it makes no difference.

This means a human's choice is the same as a machine's choice , and points to us humans having no free choice. I mean how much of a free choice can a machine have...

 

[quantumfunction]

This means a human's choice is the same as a machine's choice , and points to us humans having no free choice. I mean how much of a free choice can a machine have...

It's two different things at least in this experiment. The choice was random and controlled by a quantum random number generator.

Humans can make a random choice by flipping a shuffled deck of cards. Humans can also make choices based on information so in that sense it's different from a machine. A human can make the choice to flip over the cards and pause at every third card. So the choice is non random based on the knowledge the human has about pausing every three cards.

This can be a human making a choice to invest in stocks using the Kelly Criterion. The choice is non random based on the persons knowledge of the Kelly Criterion.

 

[bhobba]

This means a human's choice is the same as a machine's choice , and points to us humans having no free choice. I mean how much of a free choice can a machine have...

Machines don't choose by the definition of choice. Not everything in QM is like observation that has a meaning different to the usual use.

Thanks
Bill

 

[bhobba]

Whether this choice is controlled by a quantum random number generator or a human brain, it's still a free choice.

Physics is not a semantic word game. Machines do not choose. I suggest you think about why you want to use that word.

WHY DOES VICTOR'S CHOICE HAVE ANY MEANING AFTER ALICE AND BOB'S PARTICLES HAVE BEEN MEASURED?

If you say - Why does the independent entangling or not entangling by Victor have any meaning after Alice's and Bob's particles have been measured - what's going on is much clearer and less loaded with the semantic baggage of 'choice' - which in usual use means a decision by a rational agent.

This whole business has to do with the mathematics of entanglement.

Consider the entangled state 1/√2 |a>|b> + 1/√2 |b>|a>. If system 1 is observed in state |a> then system two can't be in state |a> because only |a>|b> or |b>|a> is allowed by entanglement. This means the other system must be in state |b>. It analogous to Bertlmann's socks:
http://cds.cern.ch/record/142461/files/198009299.pdf

The difference is, as Bell showed, is its different to classical correlations, but it still just a correlation.

In general all delayed choice experiments do is show in simple cases decoherence can be unscrambled - there is nothing mysterious about if the observation made later unscrambles it or not. Its only on the surface a mysterious phenomena. But when you understand all that's going on is if the decoherence is unscrambled - its actually trivial.

If people want to understand in a particular set-up how it gets unscambled then go ahead - do a post about that. But that's what's going on.

As I said, Alice and Bob measure before Victor. And they can be sufficiently separated so that their photons have never existed within a common light cone. Ergo they have no causal influence on one another, unless such is FTL. Of course, Alice and Bob DO observe their results. They are correlated if Victor later decides to entangle them. Otherwise, they are not correlated. This is the point of the experiment, that a correlation is made to occur after particles are already detected and the outcomes recorded/

As seen from the above here its very simple. It doesn't even require invoking undoing decoherence - its entirely due to if Victor entangles them or not.

I think conscious knowledge of the system is important on a fundamental level and we also see this in the delayed choice quantum eraser experiment.

Normally I wouldn't care about such semantic quibbling - if you use choice or whatever is not really germane - the issue comes when you want to use it to draw conclusions like the above. Replacing Victor etc with machines and avoiding loaded words like choice clearly shows such can not be concluded.

Thanks
Bill

 

[zonde]

Of course Victor's choice matters. That's the delayed CHOICE portion of the experiment. Here's a quote directly from the experiment.

There is another quote from the same paper:

However, there is never a paradox if the quantum state is viewed as no more than a ‘catalogue of our knowledge’2. Then the state is a probability list for all possible measurement outcomes, the relative temporal order of the three observers’ events is irrelevant and no physical interactions whatsoever between these events, especially into the past, are necessary to explain the delayed-choice entanglement swapping. What, however, is important is to relate the lists of Alice, Bob and Victor’s measurement results. On the basis of Victor’s measurement settings and results, Alice and Bob can group their earlier and locally totally random results into subsets that each have a different meaning and interpretation. This formation of subsets is independent of the temporal order of the measurements.

 

[DrChinese]

If I go to the store to buy a bag of Funyuns or a bag of Doritos and I make the choice to buy Funyuns, I then go to the cooler to buy a drink I like with my funyuns, I bump into a High School friend, he invites me to a cookout, I go and meet his sister that's in town, we start dating, get married and have 2 kids.

My choice to buy funyuns created a reality and history in this environment. I could have made a choice to buy Doritos and went straight to the checkout and never bumped into my HS friend.

This example does not serve as an analogy to the experiment at hand. Please note that NONE of the following make any difference to the experimental statistical results:

1. Whether Alice, Bob, or Victor are conscious or are robots.
2. Whether Alice or Bob are close enough to communicate or not.
3. Whether the Victor entangles before or after Alice and Bob make their observations.
4. Whether Alice makes her observation after Victor entangles, and Victor makes his decision after Bob observer.
5. Whether the photons Alice and Bob observe ever even co-existed.

The only thing that matters is the overall context, which is not limited to a classical light cone and is not constrained by classical causality (as occurs in your example). Yes, Victor's choice matters. But it can be made at any time. In your example, to be a proper analogy: you could get married to your friend's sister and later re-connect with your friend and get introduced to her.

Note to self: stay away from the funyuns. :)

 

[quantumfunction]

This example does not serve as an analogy to the experiment at hand. Please note that NONE of the following make any difference to the experimental statistical results:

The analogy was a response to people who act like Victor's choice didn't matter and it's obvious that it does. The Author's of the paper make that clear.I was then showing how choice creates reality on a quantum (Victor) or classical(funyuns) level. On a side note, I don't eat funyuns, too salty.

I'm glad you see that:

Yes, Victor's choice matters

"We found that whether Alice's and Bob's photons are and show quantum correlations or are separable and show classical correlations can be decided after they have been measured", explains Xiao-song Ma, lead author of the study.

DECIDED BY VICTOR'S CHOICE

Victor's choice created reality and that was my point about the funyun example.

If Victor decides to entangle, a history unfolds in the environment where Alice and Bob's particles are entangled. If Victor chooses not to entangle, then you have a history n that environment where Alice and Bob's particles are separable.

This all depends on CHOICE.

Victor's choice can occur after Alice and Bob's particles have been measured because there's no communication between Bob and Alice.

In general all delayed choice experiments do is show in simple cases decoherence can be unscrambled - there is nothing mysterious about if the observation made later unscrambles it or not. Its only on the surface a mysterious phenomena. But when you understand all that's going on is if the decoherence is unscrambled - its actually trivial.

This has nothing to do with unscrambling decoherence but Victor's CHOICE. Show me in the paper where it talks about unscrambling decoherence. In fact later test were done that showed choice can suppress decoherence and delay it.

Experimental demonstration of delayed-choice decoherence suppression

Wheeler’s delayed-choice experiment illustrates vividly that the observer plays a central role in quantum physics by demonstrating that complementarity or wave–particle duality can be enforced even after the photon has already entered the interferometer. The delayed-choice quantum eraser experiment further demonstrates that complementarity can be enforced even after detection of a quantum system, elucidating the foundational nature of complementarity in quantum physics. However, the applicability of the delayed-choice method for practical quantum information protocols continues to be an open question. Here, we introduce and experimentally demonstrate the delayed-choice decoherence suppression protocol, in which the decision to suppress decoherence on an entangled two-qubit state is delayed until after the decoherence and even after the detection of a qubit. Our result suggests a new way to tackle Markovian decoherence in a delayed manner, applicable for practical entanglement distribution over a dissipative channel.

http://www.nature.com/ncomms/2014/140729/ncomms5522/full/ncomms5522.html

The important thing here also is Victor's choice causes correlation in all 3 bases. It's important to look at this because you can still have superposition say in the computational basis while there's decoherence in the energy basis. There's a lot of myths out there about decoherence and it has become a catch all phrase when it's not. You can still have superposition in other bases after decoherence time and even at equilibrium.

Decoherence: myths and realities

It is therefore not correct to assume all superpositions are destroyed after the decoherence time. One needs to clearly specify in what basis the environment acts and what is its influence in other bases. We usually care about superposition in the computation basis, where useful interferences happen. Below, a few simple examples with more details are provided. Some understanding of density matrix theory is required to follow the details.

Decoherence is a process through which quantum superposition in a system is washed out due to coupling to an environment. It is a basis-dependent phenomenon, therefore, decoherence in one basis does not necessarily destroy superposition in another basis. In the weak coupling limit, when the Hamiltonian of the system is dominant and the environment is a perturbation, decoherence happens in the energy basis. In the strong coupling limit decoherence may destroy superposition in other bases.

https://dwave.wordpress.com/2011/06/10/decoherence-myths-and-realities/

This was also seen in an experiment on quantum entanglement and photosynthesis.

Quantum entanglement in photosynthetic light-harvesting complexes

Light-harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long timescales, despite the decohering effects of their environments. Here, we analyse entanglement in multichromophoric light-harvesting complexes, and establish methods for quantification of entanglement by describing necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement. These methods are then applied to the Fenna–Matthews–Olson protein to extract the initial state and temperature dependencies of entanglement. We show that, although the Fenna–Matthews–Olson protein in natural conditions largely contains bipartite entanglement between dimerized chromophores, a small amount of long-range and multipartite entanglement should exist even at physiological temperatures. This constitutes the first rigorous quantification of entanglement in a biological system. Finally, we discuss the practical use of entanglement in densely packed molecular aggregates such as light-harvesting complexes.

http://www.nature.com/nphys/journal/v6/n6/abs/nphys1652.html#supplementary-information

So, it has nothing to do with the unscrambling of decoherence. It has everything to do with Victor's CHOICE which creates a reality and history in the the environment.

 

[bhobba]

So, it has nothing to do with the unscrambling of decoherence. It has everything to do with Victor's CHOICE which creates a reality and history in the the environment.

If you keep saying it often enough it doesn't make it true. That the choices you, Victor or anyone makes creates reality is an unprovable philosophical position of zero scientific concern. You can replace what happens by say a quantum random number generator. Obviously what occurs is what happens and is in that sense reality - in QM observations such as a random quantum process are very real - it doesn't create reality - it is the reality. The same with conscious choices you make. When made it is the reality - it doesn't create reality. This is typical of philosophical arguments - it has multiple semantic interpretations that are impossible to distinguish and is one reason philosophy usually gets nowhere, and is not allowed here by forum rules. There is no way to distinguish between creates reality and is reality - its simply semantics.

Thanks
Bill

 

[quantumfunction]

If you keep saying it often enough it doesn't make it true. That the choices you, Victor or anyone makes creates reality is an unprovable philosophical position of zero scientific concern.

That's just not the case.

First you haven't shown anywhere in the paper where they talk about the unscrambling of decoherence. They talk about Victor's CHOICE. That has nothing to do with philosophy, it's the experiment.

As I showed in the last post there's a lot of myths with decoherence. It isn't a catch all phrase.

Also, Victor's choice does create reality in that local environment. It's his choice that determines which history will unfold in that environment of entangled/not entangled.

I've noticed people yell philosophy on this forum when they want to shut down debate.

 

[bhobba]

First you haven't shown anywhere in the paper where they talk about the unscrambling of decoherence..

Will you please read what I wrote. I said in this case you don't require unscrambling decoherence.

In normal day to day communication we all use words loosely. It's not usually an issue except when people read more into it than intended - which is what you have done. Here choice is inappropriate as can be seen by expressing it as I did not using the word.

If you don't move on from this semantic quibbling the mods will, correctly, shut the thread down.

Thanks
Bill

 

[quantumfunction]

Here choice is inappropriate as can be seen by expressing it as I did not using the word.

I'm not trying to express anything the way that you did. The way you express it is your opinion and has nothing to do with the way it was expressed in the published paper.

I didn't know there was a forum rule that states I can only talk about something if I put it in words that agrees with your opinion.

Again, Victor's choice determines the outcome as EXPRESSED by the published paper.

In the entanglement swapping1-3 procedure, two pairs of entangled photons are produced, and one photon from each pair is sent to Victor. The two other photons from each pair are sent to Alice and Bob, respectively. If Victor projects his two photons onto an entangled state, Alice’s and Bob’s photons are entangled although they have never interacted or shared any common past. What might be considered as even more puzzling is Peres’ idea of “delayed-choice for entanglement swapping”4,5 . In this gedanken experiment, Victor is free to choose either to project his two photons onto an entangled state and thus project Alice’s and Bob’s photons onto an entangled state, or to measure them individually and then project Alice’s and Bob’s photons onto a separable state. If Alice and Bob measure their photons’ polarization states before Victor makes his choice and projects his two photons either onto an entangled state or onto a separable state, it implies that whether their two photons are entangled (showing quantum correlations) or separable (showing classical correlations) can be defined after they have been measured.

Victor is free to choose.

In order to experimentally realize Peres’ gedanken experiment, we place Victor’s choice and measurement in the time-like future of Alice’s and Bob’s measurements, providing a “delayed-choice” configuration in any and all reference frames. This is accomplished by (1) proper optical delays for Victor’s photons and (2) a high-speed tunable bipartite state analyzer, which (3) is controlled in real time by a quantum random number generator (QRNG)6 . Both delay and randomness are needed to avoid the possibility that the photon pairs can “know” in advance which setting will be implemented after they are registered and can behave accordingly by producing results of a definite entangled or a definite separable state. Whether Alice’s and Bob’s photons can be assigned an entangled state or a separable state depends on Victor’s later choice. In Peres’ words: “if we attempt to attribute an objective meaning to the quantum state of a single system, curious paradoxes appear: quantum 2 effects mimic not only instantaneous action-at-a-distance but also, as seen here, influence of future actions on past events, even after these events have been irrevocably recorded.”4

DEPENDS ON VICTOR'S LATER CHOICE.

I'm expressing it in the way that it was published not based on your personal opinion.

 

[berkeman]

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