Physics prize puts spotlight on optics

Understanding quantum nature of light led to breakthroughs.

Work by this year's physics laureates led to a better understanding of the nature of light. Credit: M. OLDFIELD, SCUBAZOO/SPL

Three researchers who applied quantum theory to light, and built devices that are now providing the best-ever measurement of fundamental constants, have been awarded this year's Nobel Prize in Physics.

Half the award goes to the theoretician who laid the groundwork for the advances: Roy Glauber. A professor of physics at Harvard University since 1976, Glauber is a former member of the Manhattan Project — the effort that led to the development of atomic weapons during the Second World War.

John Hall of the University of Colorado in Boulder and Theodor Hänsch of Ludwig Maximilians University in Munich, Germany, share the other half for developing techniques to measure the frequency of light emitted by atoms and molecules.

Theodor Hänsch is beseiged by reporters after winning a share in this year's physics Nobel. Credit: A. ABBOTT

Hänsch was busy at his university, packing for a flight to the United States, when he heard the news. Half an hour later, he was trying to deal with the attentions of the hundred or so reporters who had arrived at his office, eager to know everything about his life. He says he never expected to win the award. “I'm overwhelmed,” he says. “I haven't absorbed it yet.”

Hänsch and Hall's work is rooted in two papers published by Glauber in 1963, which built on the excitement in the physics community generated by the development of lasers in the 1950s. The papers focused on the working of the devices that are used to measure photons of light from lasers and other sources. Glauber showed that normal statistics failed to describe the interaction between photon and detector; only an understanding of the quantum nature of the device could explain it.

Such breakthroughs turned Glauber into a major player in the emerging field of quantum optics, which applies established quantum theory to light. The fruits of the discipline were a better understanding of lasers and the process by which excited atoms and molecules emit photons of light. Hall and Hänsch independently used such results to build optical combs, which are laser devices that can measure the frequency of light sources with great precision.

Fields as diverse as navigation and cosmology are benefiting from optical combs, which are being used to develop a new generation of optical clocks — potentially capable of a precision of 1 part in 1018. Researchers studying the fine-structure constant, which determines the strength of the interaction between light and matter, are using the clocks to study whether the constant changes slightly with time. The devices could also lead to a redefinition of the second, and help to improve the precision of the navigation signals emitted by global positioning systems.

Additional reporting by Alison Abbott


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The Nobel Prize in Chemistry was announced after Nature went to press. For coverage see

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Giles, J. Physics prize puts spotlight on optics. Nature 437, 800 (2005).

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