This item appears to illuminate
the concept of entanglement in a purely physical manner making it quite
comprehensible and providing insights into what can now be done with individual
photons. This is becoming more necessary.
Do take the trouble to read through
this.
A s I have posted in the past, my
own efforts on describing the foundational fundamental particle pretty
explicitly also describes the physical nature of photons. Thus what we are seeing here can be modeled
directly, although the computer power needed is monstrous. At least we are drawing pictures of ribbons
which I suspect is an excellent analogy.
Two crystals linked by quantum physics
by Staff Writers
This splitting allows the researchers to obtain two entangled photon
halves. In other words, even though they are not in the same location, the two
halves continue to behave as if they were one.
For almost fifteen years Professor Nicolas Gisin and his physicist
collaborators have been entangling photons. If this exercise seems
to them perhaps henceforth trivial, it continues to elude us ordinary humans.
The laws that govern the quantum world are so strange that they
completely escape us human beings confronted with the laws of the macroscopic
world. This apparent difference in nature between the infinitesimally small and
our world poses the question of what link exists between the two.
However these two worlds do interact. To realise this, one must folow
the latest experiment of
the Group of Applied Physics (GAP). Nicolas Gisin, researcher Mikael Afzelius
and their team have actually produced the entanglement of two macroscopic crystals,
visible to the naked eye, thanks to a quantum particle, a photon, otherwise
known as a particle of light.
To achieve this exploit, the physicists developed a complex device to
which they hold the key. After a first system that
allows them to verify that they've actually managed to release one, and only
one, photon, a condition essential to the success of the experiment, a second
de- vice "slices" this particle in two. [surely photon is
meant here]
This splitting allows the researchers to obtain two entangled photon
halves. In other words, even though they are not in the same location, the two
halves continue to behave as if they were one.
Wait for the photons to exit
The two halves are then each sent through a separate crystal where they will interact with the neodymium atoms present in its atomic structure. At that moment, because they are excited by these entangled photons, the neodymium lattices in each crystal likewise become entangled. But how can we be certain that they've actually reacted to the two photon halves?
That's simple ... or nearly! They just have to wait for the two
particles to exit the crystals - since they exit after a rather brief period of
about 33 nanoseconds - and to verify that it really is the entangled pair.
"That's exactly what we found since the two photons that we cap-
tured exiting the crystals showed all the properties of two quantum particles
behaving as one, characterised by their simultaneity in spite of their
separation", Fe'lix Bussie`res rejoices, one of the authors of the
article.
In addition to its fundamental aspect, this experiment carries with it
potential applications.
Actually, for the specialists in quantum entan- glement, this phenomenon has
the unpleasant habit of fading when the two entangled quantum objects are too
far from one another.
This is problematic when one envisions impregnable quantum cryptography
networks which could link two distant speakers separated by several hundreds or
even thousands of kilometres.
"Thanks to the entanglement of crystals, we can now imagine
inventing quantum repeaters", Nicolas Gisin explains, "in other
words, the sorts of terminals that would allow us to relay entanglement over
large distances. We could then also create memory for quantum com-
puters."
Entanglement still has many surprises in store for us.
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