Friday, January 23, 2009

entangled quantumly

From Scientific American: Quantum Entanglement Benefits Exist after Links Are Broken, Quantum Leap: Information Teleported between Ions at a Distance

Two really interesting articles on quantum entanglement. According to wikipedia, quantum entanglement is "a quantum mechanical phenomenon in which the quantum states of two or more objects are linked together so that one object can no longer be adequately described without full mention of its counterpart — even though the individual objects may be spatially separated."

In the first article, Seth Lloyd, a quantum physicist at MIT, discovers that there is some sort of lingering connection between particles even after they've disentangled. By applying this, he developed the idea of quantum illumination, where something (a camera, satellite, x-ray machine, whatever), could entangle photons and send one set to the object being sensed, with the other set being used for reference, so that when the returning photons bring information back, any noise created by any unrelated photons could be filtered out. And, "[i]f quantum illumination works, Lloyd suggests it could boost the sensitivity of radar and x-ray systems as well as optical telecommunications and microscopy by a millionfold or more."

The second article describes how researchers, led by Stephen Olmschenk, a grad student at UMD College Park, "succeeded in teleporting quantum information between ytterbium ions (charged atoms) three feet (one meter) apart." The article describes the process:
Information is teleported from one ion to another by encoding quantum information onto the first ion. Once the ion is entangled with another, the state of each ion is indefinite until the first one is measured—an action that projects the other ion into one of two states. Conventional (nonquantum) communication channels relay information, gleaned from the first ion's measurement, as to which of those two states is correct, and a pulse of microwave energy sets the second ion into the state representing the information encoded on the first.
What peaked my interest about this (besides it being awesomely cool) was a couple of sci-fi books I read a few years ago, Metaplanetary (2001) and Superluminal (2004) by Tony Daniel, which are set in the future where quantum communication is the basis for society and technology. Great books. Anyway, the thought of actually applying quantum entanglement and communication to real technology is awesome. We will never know everything.

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