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French, American physicists who study light awarded Nobel

Their work may lead to super accurate clocks

NEW YORK — Two physicists who developed techniques to study the interplay between light and matter on the smallest imaginable scale were awarded the Nobel Prize in Physics on Tuesday. They are Serge Haroche, of the College de France and the Ecole Normale Superieure, in Paris, and David Wineland, of the National Institute of Standards and Technology and the University of Colorado.

They will split about $1.2 million and receive their award in Stockholm on Dec. 10.

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Their work, the academy said, enables scientists to directly observe some of the most bizarre effects — like the subatomic analogue of cats who are alive and dead at the same time — predicted by the quantum laws that prevail in the microcosm, and could lead eventually to quantum computers and super accurate clocks.

Scientists have known for a hundred years now that atoms are not like you and me. On the smallest scales of nature the common sense laws of science had been overthrown by the strange house rules of quantum mechanics, in which physical systems were represented by mathematical formulations called wave functions that encapsulated all the possibilities of some event or object. Light or a subatomic particle like an electron could be a wave or a particle depending on how you wanted to look at it, and causes were not guaranteed to be linked to effects. An electron could be in two places at once, or everywhere until someone measured it, courtesy of Heisenberg’s Uncertainty principle.

Erwin Schroedinger, one of the founders of the theory, once complained that according to quantum principles a cat in box would be both alive and dead until somebody looked at it.

Until recent years this was all philosophy, and physicists could comfort themselves with the realization that quantum mechanics works so spectacularly well — every time you turn on your computer, for example — that for some of them the real problem is why the ordinary world does not work that way; why, for example, your sunglasses are not simultaneously in the car or on the shelf when you want them.

Now scientists like Haroche and Wineland and their colleagues have been able to direct experiments and catch nature in the act of being quantum and thus explore the boundary between quantum reality and normal life. Their work involves isolating the individual nuggets of nature — atoms and the particles that transmit light, known as photons — and making them play with each other.

Wineland’s work has focused on the matter partner in the light-matter dance. He and his colleagues trap charged beryllium atoms, or ions, in an electric field and cool them so that they are barely moving.

In one set of experiments they then tapped the beryllium ions with lasers with just enough energy to produce another kind of cat state. In this one, the outermost electrons in the ion are stuck between two of the permitted orbits around the beryllium nucleus; as a result they oscillate back and forth and the beryllium ion is in two energy states at once.

Because cold atoms vibrate and emit light at very precise frequencies, Wineland and his colleagues have also used their trapped ions to make the world’s most accurate clocks. Modern day atomic clocks are based on the cesium atoms, which vibrate in the microwave range of frequencies, but beryllium vibrates 100 times faster. A good optical clock would have lost only 5 seconds over 13.7 billion years.

Haroche, conversely traps photons, the particles that transmit light, in a mirrored cavity whose walls are so finely polished that one photon will bounce back and forth for a tenth of a second before leaking out or being absorbed. Then he sends in a single atom, as a spy, to interact with the light.

Normally to detect light is to destroy it. But in one case by observing subtle effects of the light on the atoms, he and his colleagues could count the photons without destroying them.

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