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Entanglement exceeds time - Comment on 2013 June 5 (2)

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The measuring at the first photon influences the state of a photon of which at the point of time of measurement it was not even clear that it is getting produced. But one could also argue that the measurement at the fourth photon influences the state of the first one retrospectively. Read more:

Here extracts from a report I read today:

 

Tricking with quanta

Researchers have shown that entanglement also exceeds time.

Entanglement belongs to the strangest characteristics of quantum mechanics: Two particles can be connected together very closely in such a way that a measurement at one of the two instantaneously also fixes the state of the other, which is up to then undefined – and that despite the spatial distance between the two. As Israeli researchers have now shown entanglement does not only seem to implicate one “ghostly remote effect” in space, but also one in time. The group of Hagai Eisenberg of the University of Jerusalem could entangle two photons with each other, which did not exist at the same time.

The experiment is based on a technique which allows entangling two photons, which never had direct contact with each other. For this one first produces with a laser and a none-linear crystal two pairs of entangled photons at different places. Then one brings together the second photon of the first pair and the first photon of the second pair over fibre optic cables and takes a special measurement, through which the two get entangled together. This liaison also influences the partner photons. They come off their relationship, and the entanglement slops over from the first to the fourth photon. When one now measures the polarisation of these two photons regarding certain directions, one will notice that the results are correlated upon a typically quantum mechanical way, although the two particles never met each other.

Already a year ago the working group of Anton Zeilinger of the University of Vienna had shown that the quantum correlation between the photons also then remains in existence when one delays the entangling measurement at the second and at third photon so long until the individual measurements are finished: Although the first and the fourth photon cannot yet know that they are getting entangled together later, the measuring results anticipate this fact.

The group of Eisenberg has now intensified this situation even more. In their experiment the second photon pair is produced only after the polarisation measurement at the first photon. The second photon is fed into a fibre optic cable and delayed until the generation of the second pair. Then the entangling measurement takes place as before, through which also the first gets entangled with the fourth photon – with the difference that the first photon at his point in time already no longer exists because it was absorbed by the measuring apparatus. Nevertheless the researcher could prove the typical quantum correlation between the first and the fourth photon after also the latter had been surveyed.

When one wants it so, then the measuring at the first photon influences the state of a photon of which at the point of time of measurement it was not even clear that it is getting produced. But one could also argue that the measurement at the fourth photon influences the state of the first one retrospectively, said Eisenberg.

 

See
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220
2009 Dec 01 – Time and Space Concept
2010 Jul 31 – The quantum mechanics of time travel
2011 Sep 27 – Weird relativity and quantum physics
2012 May 23 – Does death exist?

 

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