Experiment with single photons

[BenVitale]

I came across an article in HuffPost entitled : Does the Past Exist Yet? Evidence Suggests Your Past Isn't Set in Stone

Could anyone comment on the following quote:

"The histories of the universe," said renowned physicist Stephen Hawking "depend on what is being measured, contrary to the usual idea that the universe has an objective observer-independent history."

In 2002, scientists carried out an amazing experiment, which showed that particles of light "photons" knew -- in advance −- what their distant twins would do in the future. They tested the communication between pairs of photons -- whether to be either a wave or a particle. Researchers stretched the distance one of the photons had to take to reach its detector, so that the other photon would hit its own detector first. The photons taking this path already finished their journeys -− they either collapse into a particle or don't before their twin encounters a scrambling device. Somehow, the particles acted on this information before it happened, and across distances instantaneously as if there was no space or time between them. They decided not to become particles before their twin ever encountered the scrambler. It doesn't matter how we set up the experiment. Our mind and its knowledge is the only thing that determines how they behave. Experiments consistently confirm these observer-dependent effects.

Could you post links to this research, and comments on this experiment?

 

[zhermes]

This is a very questionable interpretation of quantum entanglement.
For reviews, see:
http://en.wikipedia.org/wiki/Quantum_entanglement
http://arxiv.org/abs/quant-ph/0702225

Hawking is referring to particular unmeasured quantities of particular particles. A 'history' on the other hand, refers to a set series of interactions--which, in interacting, have already been 'measured.' Which means that the results are (except for rare exceptions, e.g. at black-hole event horizons) agreed upon by any observer.

 

[DrChinese]

There are a variety of ways to interpret the results of experiments such as this one, and the above is one:

http://arxiv.org/abs/quant-ph/0201134

"A seemingly paradoxical situation arises — as suggested by Peres [4] — when Alice’s Bellstate analysis is delayed long after Bob’s measurements. This seems paradoxical, because Alice’s measurement projects photons 0 and 3 into an entangled state after they have been measured. Nevertheless, quantum mechanics predicts the same correlations. Remarkably, Alice is even free to choose the kind of measurement she wants to perform on photons 1 and 2. Instead of a Bell-state measurement she could also measure the polarizations of these photons individually. Thus depending on Alice’s later measurement, Bob’s earlier results either indicate that photons 0 and 3 were entangled or photons 0 and 1 and photons 2 and 3. This means that the physical interpretation of his results depends on Alice’s later decision.

"Such a delayed-choice experiment was performed by including two 10 m optical fiber
delays for both outputs of the BSA. In this case photons 1 and 2 hit the detectors delayed by about 50 ns. As shown in Fig. 3, the observed fidelity of the entanglement of photon 0 and photon 3 matches the fidelity in the non-delayed case within experimental errors. Therefore, this result indicate that the time ordering of the detection events has no influence on the results and strengthens the argument of A. Peres [4]: this paradox does not arise if the correctness of quantum mechanics is firmly believed."