- #421
DrChinese
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iste said:1. The point is that it seems to be the case that if you take all of the possible data from 2 & 3, there is always ways of sorting the data where you have Bell state correlations, separable correlations and no correlations whatsoever. The fact that you can mix the Bell state data and make the correlations in other bases disappear is indicative of this because even though those correlations have disappeared, its just the same data mixed up. The new mixed up data is then statistically the same as the separable measurements data (even though it is made up of swap data).
And this is also pretty clearly the case in the part where they unambiguously describe mixing Bell states and report the statistical correlations they do and do not find. The mixing I am referring to is very unambiguously decribed in the paper you linked. I think you need to re-read that part of the paper.
2. They are in precisely the sense I mean - in the sense that the particles possess correlations and if you should chose to make measurements you would find those correlations. The fact that you happen to choose to measure some bases or not is immaterial, just like the fact that the entangled photons will have correlations in all bases but you clearly cannot ever simultaneously measure them at the same time.
Again, just trying to present the actual facts.
1. There is no "mixing" in this paper, or any others I cite. Respected scientists do not "mix" statistics to deceive readers. They present a real effect that has been replicated in various manners in other experiments. I might have hoped that it would not be necessary to say that, since one of the authors shared a Nobel for this and other ground-breaking work. But perhaps some quotes from the paper itself will be convincing:
"Since Peres' proposal [circa 1999], there have been pioneering delayed entanglement swapping experiments. However, none of these demonstrations implemented an active, random and delayed choice, which is required to guarantee that the photons cannot know in advance the setting of the future measurement. Thus, these experiments in principle allowed for a spatiotemporal description in which the past choice event influences later measurement events. Our experiment demonstrates entanglement-separability duality in a delayed-choice configuration via entanglement swapping for the first time. This means that it is possible to freely and a posteriori decide which type of mutually exclusive correlations two already earlier measured particles have. They can either show quantum correlations (due to entanglement) or purely classical correlations (stemming from a separable state).
"For each successful run (a 4-fold coincidence count), not only Victor’s measurement event happens 485 ns later than Alice and Bob’s measurement events, but Victor’s choice happens in an interval of 14 ns to 313 ns later than Alice and Bob’s measurement events. Therefore, independent of the reference frame, Victor’s choice and measurement are in the future light cones of Alice and Bob’s measurements. Given the causal structure of special relativity, i.e. that past events can influence (time-like) future events but not vice versa, we explicitly implemented the delayed-choice scenario as described by Peres.
"Fig. 3A shows that when Victor performs the Bell-state measurement and projects photons 2 and 3 onto
|Φ−〉23, this swaps the entanglement, which is confirmed by significant correlations of photons 1 and 4 in all
three bases. ... On the other hand, when Victor performs the separable-state measurement on photons 2 and 3 and does not swap entanglement, the correlation only exists in the |𝐻〉/|𝑉〉 basis and vanishes in the |+〉/|−〉 and|𝑅〉/|𝐿〉 bases, as shown in Fig. 3B. This is a signature that photons 1 and 4 are not entangled but in a separable state. ... For each pair of photons 1&4, we record the chosen measurement configurations and the 4-foldcoincidence detection events. All raw data are sorted into four subensembles in real time according to Victor’s choice and measurement results. After all the data had been taken, we calculated the polarization correlation function of photons 1 and 4. It is derived from their coincidence counts of photons 1 and 4 conditional on projecting photons 2 and 3 to |Φ−〉23 = (|𝐻𝐻〉23 − |𝑉𝑉〉23)/√2 when the Bell-state measurement was performed, and to |𝐻𝐻〉23 or |𝑉𝑉〉23 when the separable state measurement [SSM] was performed."
Note that the only Bell state statistics that are being presented are for the |Φ−〉 case, and the |Φ+〉 case is not considered for technical reasons. For the Separable state stats, the comparable stats to the |Φ−〉 case are presented. The results are "apples to apples". It is a simple matter to see the critical difference between the 3a graph (Victor executes a swap) and the 3b graph. This difference is simply a result of Victor's decision (actually a random choice) to swap or not.
So no matter what you seem to think, there is a demonstrable effect that is strictly dependent on interfering overlap in the beamsplitter: "The Bell-state measurement (BSM) corresponds to turning on the switchable quarter-wave plates..." while the SSM (separable) corresponds to leaving them off. Note that other cited implementations of switching between the BSM vs. SSM (i.e. swap or not) use delay to create distinguishable photons.
2. There is no such thing as "transitive" statistical relationships between independently created entangled pair streams such as 1&2 and 3&4 (that would also yield a underlying relationship between 1&4). I don't know where you got this idea from, but you won't find any support for what you say in the literature. Although if I'm wrong, you can always correct me with a suitable citation.
A broken clock is right twice a day - and it is equally true that there is a basis (H/V specifically, as shown in Figure 3) which do correlate. But that correlation is quite limited, and can easily be seen for what it is. Look at the other bases such as +/- or L/R and you can see the unambiguous results.