Dec 1, 2011

Real Diamonds' communication

The vibrational states of two spatially separated, millimeter-sized
diamonds are entangled at room temperature by scattering a pair of
strong pump pulses (green). The generated motional entanglement is
verified by observing nonclassical correlations in the inelastically
scattered light.

(ISNS) -- Researchers working at the Clarendon Laboratory at the
University of Oxford in England have managed to get one small diamond
to communicate with another small diamond utilizing "quantum
entanglement," one of the more mind-blowing features of quantum
physics.

Entanglement has been proven before but what makes the Oxford
experiment unique is that concept was demonstrated with substantial
solid objects at room temperature.

Previous entanglements of matter involved submicroscopic particles,
often at cold temperatures.

This experiment employed millimeter-scale diamonds, "not individual
atoms, not gaseous clouds," said Ian Walmsley, professor of
experimental physics at Oxford's Clarendon Laboratory, one of the
international team of researchers.

The experiment is reported in this week's edition of Science.

When zapping one artificial diamond with ultrashort laser pulses they
managed to change the vibrations of a second diamond sitting a half a
foot away without touching it.

Entanglement originated in the mind of Albert Einstein, who ironically
came up with the notion trying to disprove quantum mechanics, a branch
of physics he mistrusted all his life.

Under the theory, if two particles, say electrons, are created
together, some of their attributes will become "entangled." If the two
are then separated, doing something to one instantly affects the
other. This would happen whether they were next to each other or
across the universe.

For instance, electrons act as if they have tiny bar magnets that
point up or down, described by an attribute called "spin." If the two
electrons are entangled through their spins -- up or down -- and a
scientist measures the spin of one, the spin of the other will react
even if one is on a lab table in Oxford and the other were on a planet
near the star Antares, 1,000 light years away. Instantly.

This would mean that the information about the change traveled faster
than the speed of light -- which Einstein said was impossible -- or
that long distances are some kind of illusion.

Einstein disparaged it as "spooky action at a distance." The German
physicist Erwin Schrodinger used the term "entanglement" in a letter
to Einstein. He didn't believe in quantum mechanics either.

"I think I can safely say no one understands quantum mechanics," the
late physicist Richard Feynman once famously explained.

Nonetheless, quantum mechanics is now the paradigm for nature at the
atomic level. It serves as the foundation of much of modern
technology, from lasers to transistors. And entanglement comes as part
of the package. Physicists have been demonstrating it in laboratories
since the 1980s, and it is being used in laboratories experimenting
with the building blocks of quantum computers.

The diamonds Walmsley and his international team used were
approximately 3 millimeters (a tenth of an inch) square and 1
millimeter thick.

"We used short pulse lasers with pulse durations of around 100
femtoseconds (a quadrillionth of a second). A femtosecond is to a
second as a nickel is to the debt of the federal government generally
speaking," he said.

They chose diamonds because they are crystals, so it was easier to
measure molecular vibrations, and because they are transparent in
visible wavelengths. Light from the lasers altered a kind of mass
vibration in the diamond crystal called phonons, and the measurements
showed they were entangled: The vibrations of the second diamond
reacted to what happened to the vibrations of the first.

Performing the experiment with ultrafast laser pulses enabled the
researchers to catch entanglement, which is usually very short-lived
in large objects at room temperature.

"It remains a counterintuitive way of thinking about objects,"
Walmsley admitted.

"It's a very nice and clever piece of work with potentially big
implications," said Sidney Perkowitz, a physicist at Emory University
in Atlanta, and author of "Slow Light: Invisibility, Teleportation and
Other Mysteries of Light," a book partially about entanglement. The
macroscopic size, and the fact that this was done at room temperature,
would be important steps toward a practical quantum technology for
telecommunications and computing, and toward deeper understanding of
how the quantum world and the human-scale world are related."

)))))))))))))))))))))))))))))))))))))(((((((((((((((((((((((((((((((((((((((((((((((((