Quantum Wizardry Wins Nobel Recognition

The 2012 Nobel Prize for Physics was awarded to an American and a French researcher for “ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems.”

David Wineland of the National Institute of Standards and Technology in Boulder, Colorado and Serge Haroche of the Collège de France in Paris are both APS Fellows. Their respective work on different quantum systems has helped to lay the groundwork for fundamentals of quantum computers and the next generation of atomic clocks.  

Wineland’s team developed a technique to prepare individual charged atoms in a superposition of their two lowest energy states. To do this, they confined a system of ions in an electric field and cooled them to their lowest energy state. The team then exposed the ions to a finely tuned laser pulse, which effectively created a superposition of the ground state and the next excited state.

Haroche came up with a complementary technique, which used atoms to measure the quantum state of a photon. He confined microwave photons in a specially designed optical cavity about three centimeters in size. The walls of the cavity were reflective and cooled to nearly absolute zero so the photons could bounce back and forth billions of times. The team then fired a doughnut-shaped Rydberg atom through the cavity and measured the energy shift of the atom, which they could use to reconstruct the quantum state of the trapped photons.  

The subtle changes to the Rydberg atom’s energy states showed that the quantum superpositions of individual photons could be detected. Moreover, physicists using this information could reconstruct the wave function of the photon as it collapsed.

“I use atoms to study the photons and he uses photons to study atoms,” Haroche told the Nobel website. “So, it’s really symmetrical and, at some point during our work, we published papers back-to-back. Just by chance, it happened that we are doing similar things on his atoms and my photons.”

The ion traps invented by Wineland have become important tools for developing applications He has already used the traps to develop “optical” atomic clocks one hundred times more accurate than the current “cesium standard” used today. Other researchers have taken the accuracy afforded by an optical clock and used it to detect the subtle variation in the flow of time caused by the different pull of gravity at two points a foot apart in altitude.  

Ion traps have also been turned into the fundamental processing units of a future quantum computer. Each quantum bit of information, instead of only being either a 1 or a 0, can be both simultaneously, increasing the processing power over conventional computers by an exponential amount. In July of 1995, Wineland and his team were the first to demonstrate a simple logic gate using these qubits, effectively the first basic computation using a quantum processor.

Wineland, who was sleeping when he first received the call from Stockholm at four in the morning, said that it was a “wonderful surprise” to win the award.

“It’s always been great [and] really exciting to be in this field,” Wineland told the Nobel website shortly after he received the news.

Wineland previously was awarded the APS Davisson-Germer Prize in Atomic or Surface Physics in 1990, and the 2001 Arthur L. Schawlow Prize in Laser Science. Haroche was APS’s Beller lecturer at the 1996 DAMOP meeting, an honor which brings distinguished international physicists to speak at APS meetings. APS president Robert Byer commended the two winners of the prize.

“Haroche and Wineland have both done beautiful research vital to the technology that truly makes this the century of the quantum,” Byer said. “Modern telecommunications rely on quantum technology, and things like the GPS system so many people use on a daily basis wouldn’t be possible without ultra-precise clocks that exploit quantum effects of the type they explored. Someday, computers built with quantum mechanical systems, much like those in the labs of Haroche and Wineland, may solve problems far beyond the capabilities of even the most advanced of today’s computers. It’s certainly amazing work these physicists have done, and continue to do, and well worth the Nobel committee’s recognition.”