Quantum-control pioneers bag 2012 Nobel Prize for Physics
Oct 9, 2012 9 comments
The 2012 Nobel Prize for Physics has been awarded to Serge Haroche and David Wineland for their work on controlling quantum systems. The prize is worth SEK 8m (£750,000) and will be shared by the pair, who will receive their medals at a ceremony in Stockholm on 10 December.
According to the prize citation, Haroche and Wineland won "for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems".
Haroche is a French citizen and works at Collège de France in Paris. Wineland is a US citizen and works at the National Institute of Standards and Technology in Boulder, Colorado.
In a statement, the Royal Swedish Academy of Sciences said "Serge Haroche and David Wineland have independently invented and developed methods for measuring and manipulating individual particles while preserving their quantum-mechanical nature, in ways that were previously thought unattainable".
According to Nobel committee member Anne L'Huillier, the pair's work represents "the first tiny steps towards building a quantum computer".
Quantum-optics pioneer Alain Aspect of Laboratoire Charles Fabry in Paris told physicsworld.com "Observing, manipulating and controlling individual quantum systems has been a major breakthrough of the last few decades. Schrödinger doubted that it might ever be possible, but this year's laureates have done it."
Haroche was born 1944 in Casablanca, Morocco, and in 1971 gained a PhD from Université Pierre et Marie Curie in Paris. He shares half of the prize for developing a new field called cavity quantum electrodynamics (CQED) – whereby the properties of an atom are controlled by placing it in an optical or microwave cavity. Haroche focused on microwave experiments and turned the technique on its head – using CQED to control the properties of individual photons.
In a series of ground-breaking experiments, Haroche used CQED to realize Schrödinger's famous cat experiment in which a system is in a superposition of two very different quantum states until a measurement is made on the system. Such states are extremely fragile, and the techniques developed to create and measure CQED states are now being applied to the development of quantum computers.
Had to sit down
In a telephone interview with Swedish journalists shortly after the announcement was made, Haroche said that he knew that he had won the prize when his mobile phone rang this morning as he was out walking and a Swedish number was on the display. "I sat down on a bench before I answered," he said. Although Haroche knew that he was in the running for the prize, he was overwhelmed upon hearing the news. He said that he will enjoy a glass of champagne at lunch with family and friends then "go back to the office to celebrate with colleagues".
Haroche also said that he was "glad to share the prize with Dave Wineland – he is a fantastic physicist and to be in his company is certainly a great pleasure for me and a great recognition".
Wineland returned the compliment by saying, "[Haroche] and I have been friends for a long time, so it’s nice to share it with him".
Master of ion control
David Wineland was born in 1944 in Milwaukee, Wisconsin, and received his PhD in 1970 from Harvard University. As well as being Group Leader and NIST Fellow at the National Institute of Standards and Technology, he also has an appointment with the University of Colorado at Boulder.
Wineland bagged his half of the Nobel for his ground-breaking work on the quantum control of ions. One of his many achievements was the creation and transfer of a single ion in a Schrödinger’s cat state using trapping techniques developed at NIST. Ion traps are created in ultrahigh vacuum using carefully controlled electric fields and a trap can hold just one ion or several in a row.
Ions vibrate as they are held in a trap, and this vibrational energy must be removed in order to cool the ion to its lowest energy state. To achieve this cooling, Wineland developed a laser-based technique to remove quanta of vibrational energy from ions. This "sideband" technique of cooling can also be used to put an ion into a superposition of states – including a Schrödinger's cat state.
Wineland has also used ion-control techniques to develop extremely accurate optical clocks, as well as circuits for quantum computers.
Groundwork for quantum information
Rainer Blatt of the University of Innsbruck in Austria does experiments in both CQED and ion trapping, and he told physicsworld.com that the Nobel committee chose well in awarding the prize to Haroche and Wineland. Blatt points out that the pair developed similar quantum-control techniques for use on different physical systems – techniques that have laid the groundwork for many of today's nascent quantum-information systems.
Blatt cites Wineland's 2008 development of "quantum-logic spectroscopy" – which allows a single ion to be used as an optical clock – as an important application of the control techniques, along with the creation in 2009 of a small-scale device that performs all the functions required in large-scale ion-based quantum processing.
Haroche's work provides a framework for controlling the interaction between a single atom and a single photon – something that Blatt says is currently being used to develop ways of exchanging quantum information between atoms and photons. This could allow physicists to create quantum computers in which data are stored in stationary quantum bits (qubits) based on atoms, which are relatively stable over long periods of time. Data could then be transmitted between atoms using photons, which can preserve their quantum information while travelling relatively large distances.
About the author
Hamish Johnston is editor of physicsworld.com