Roland Piquepaille's Technology Trends
How new technologies are modifying our way of life

dimanche 6 juillet 2003

In this article, NewsFactor Network tells us that "futuristic communications satellites may one day move information instantaneously over vast distances, making a conversation across 30 light years seem like a phone call between New York and Tokyo."

By co-opting the quirky properties of quanta -- basic, sub-atomic units of mass and energy -- quantum comsats could "overcome the principle limitations of Earth-bound technology," says Markus Aspelmeyer, a physicist at the University of Vienna's Institut für Experimentalphysik in Austria.
"Our work demonstrates for the first time, that experiments for entanglement-based quantum-communication schemes based on satellites are feasible with current technology," Aspelmeyer claims.

First, let's look at the properties of the photons he wants to use.

The strangest property of a photon may be its ability to communicate faster than its own speed -- the speed of light. Scientists can create so-called "entangled photon pairs" that have the peculiar ability to instantaneously influence one another no matter how far apart they are.
Measuring the spin state of one photon in an entangled pair instantly reveals the state of the other -- spin up for the first instantly means spin down for the second, whether 30 meters or 30 light years separate the two particles. They can never exist in the same spin state at the same time.

Now, let's look at an example.

In a three-photon scenario, a researcher in the U.S. might measure spin up -- a Morse dot -- for the first photon, which means the satellite-bound photon is spin down. A photon in France -- also entangled with the satellite bound cohort, then instantly reads spin up -- a dot delivered faster than Morse -- or Einstein -- ever could have imagined.
"The use of entangled photons for quantum cryptography was shown experimentally by different groups for long distances using optical fibers," University of Geneva physicist Ivan Marcikic told NewsFactor. "By using satellites, this distance becomes several orders of magnitude longer. It is thus a new approach to increase the distance between two entangled photons."

But don't expect to be able to communicate with other civilizations living hundreds or thousands of light years away from us anytime soon.

For more information, read the pages about the Physics of Quantum Information provided by the University of Vienna's Institut für Experimentalphysik.

Source: Mike Martin, NewsFactor Network, July 3, 2003

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