As I predicted earlier in the week, this year’s Nobel Prize for Physics did not go to Higgs et alli. What I was unable to predict was that the Prize would go to Serge Haroche (Collège de France and Ecole Normale Supérieure) and David J. Wineland (NIST and University of Colorado Boulder) ”for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems.”
Usually when quantum phenomena are studied experimentally, the experiments are performed upon large ensembles of particles, since such systems are more readily accessible via experiment. These two gentlemen, however, pioneered methods for performing experiments involving the study of the quantum behavior of individual particles. This is no small feat.
The biggest challenge here is that of measuring the quantum state of an individual particle without destroying that state. In general, measuring some quantum property of a photon (such as its polarization) tends to require destroying the photon. The work recognized by this prize works around that.
Serge Haroche’s Work
Serge Haroche and his colleagues trapped microwave photons in a cavity lined with superconducting mirrors. (Since the mirrors are superconducting, they exclude magnetic fields, which bring the mirrors closer to being perfect reflectors.) This effectively allowed photons trapped within the cavity to bounce around within it billions of times, containing the photons for a prolonged period of time (more than a tenth of a second, which is practically an eternity in the quantum world).
Rydberg atoms (atoms whose electrons are in such an excited state that they are barely bound to the nuclei) were then sent through the chamber one at a time. A comparison of the atoms’ states before and after their transit of the photon trap allowed researchers to non-distructively determine the states of the photons within.
- Serge Haroche, “Entanglement, Decoherence and the Quantum/Classical Boundary“, Physics Today (July 1998), pp. 36-42.
- M. Brune et al., “Manipulation of photons in a cavity by dispersive atom-field coupling: Quantum-nondemolition measurements and generation of “Schrödinger cat” states“, Physical Review A 45:7, 5193 (1992).
David Wineland’s Work
Earlier researchers had pioneered the technique of using lasers to cool and trap individual ions, work which was recognized with the 1997 Nobel Prize in Physics. (Of of the recipients of that prize was Steven Chu, currently the US Secretary of Energy.) Wineland and his colleagues took this a step further, devising methods for manipulating the ions and measuring their quantum states. The trapped ion sits at the intersection multiple oscillating electric fields, rising up and down periodically like a cork on a rippling pond. The control laser is then used to probe the ion’s quantum properties.
By the way, I should point out that Wineland and his cohorts have more recently used these techniques to develop an atomic clock so accurate that it can sense the slight relativistic time dilation caused by simply lowering the clock a mere 30cm further into the Earth’s gravity well.
- C. Monroe and D. Wineland, “Quantum Computing with Ions“, Scientific American, August 2008, p. 64.
- C. Monroe et al., “A “Schrödinger Cat” Superposition State of an Atom“, Science 272:1131 (1996).
Where to from Here?
The most immediate application of this work is in the field of quantum computing. In order to ever be able to successfully build quantum computers, the ability to poll, set, and maintain the quantum states of individual particles without quantum decoherence (the loss of quantum order due to interactions with other particles and fields in the environment) setting in is of paramount importance.
Congratulations to Drs. Haroche and Wineland.
- Nobel Press Release
- Summary for Non-Technical Readers
- Technical Description
- IOP’s 2012 Nobel Prize Collection – papers published by the winners in IOP publications, free for download through February 2013.
More coverage of the Prize elsewhere:
- Finally, Schrodinger’s Cat Hits A Nobel!
- The 2012 Nobel Prize in Physics: Trapping and Measuring Particle States « Galileo’s Pendulum
- Quantum Physics Is Very Real | Of Particular Significance
- What’s So Interesting About Single Quantum Systems? Physics Nobel 2012 – Uncertain Principles
- Congratulations to Dave Wineland, Serge Haroche, and KSC – Uncertain Principles
- Nobel Prize to Haroche and Wineland | Cosmic Variance | Discover Magazine
- Guest Post: John Preskill on Individual Quantum Systems | Cosmic Variance | Discover Magazine
- Nobel Physics Prize Goes to Haroche and Wineland – NYTimes.com
- 2012 physics Nobel recognizes experiments probing quantum world | Physics | Science News
- BBC News – Physics Nobel goes to Serge Haroche and David Wineland
- Nobel Prize 2012: Haroche & Wineland : Nature Physics : Nature Publishing Group
- Physics Nobel for quantum optics : Nature News & Comment
- Nobel Awarded to Scientists Who Learned to Control Quantum Systems | Wired Science | Wired.com
- Physics Buzz: All the Trappings of the 2012 Nobel Prize in Physics
- Serge Haroche and David Wineland share this year’s Nobel Prize in Physics | Physics Update – Physics Today