A good thing about a blog is that when my friends win prizes I have the opportunity to say nice things about them. This seems to be happening a lot lately (Kitaev, Wineland, Kimble, Hawking, Polchinski, …).
Today’s very exciting news is that Ignacio Cirac and Peter Zoller have won the 2013 Wolf Prize in Physics “for groundbreaking theoretical contributions to quantum information processing, quantum optics, and the physics of quantum gases.”
Spurred by the recent discovery of Shor’s algorithm, in mid-1994 Jeff Kimble and I started what we called the “Quantum computing club” at Caltech, a series of informal meetings in which our groups got together to talk about quantum information processing. Seth Lloyd, in the midst of a transition from Los Alamos to MIT, was often in town and took part in the discussions. Not knowing much about the topic at the time, I did more listening than talking, learning especially from Seth and Jeff’s amazingly erudite grad student Hideo Mabuchi.
In January 1995, Peter Zoller stopped by for a brief visit, and I suppose that must have been when we first met. Peter told us about his latest work with Ignacio, in which they proposed a method for executing a universal set of quantum gates acting on qubits encoded in the internal states of trapped ions. Their crucial new idea was that the quantized vibrations of the ions in the trap (“phonons”) could serve as a quantum bus, enabling highly controllable interactions between ions. Much of the quantum optics background behind the proposal was new to me, but after hearing these ideas I decided I better find out what an ion trap is.
The Cirac-Zoller proposal was electrifying to me and others, because it made quantum computing not just an abstract concept but something we could envision as a concrete and plausible physical system. Just months passed before Dave Wineland’s group achieved the first laboratory demonstration of the proposal, launching advances in ion-trap quantum computing that continue to this day. And this pioneering work by Cirac and Zoller stirred many other physicists to make further ingenious proposals for realizing quantum computing in other physical systems.
I think I first met Ignacio at a workshop in Santa Barbara in the fall of 1996, where he told me about his work in progress with Zoller, Kimble, and Mabuchi on using photons to distribute entanglement in a quantum network. The tricky part of their proposal concerned how to ensure that a photon arriving at a node in the network would be absorbed rather than reflected. I found it delightful that this problem could be solved by arranging for the photon wave packet to be time symmetric, so its absorption would be related to photon emission by time reversal. This paper was one of the first and most important concerning photons as “flying qubits” in a network.
It would be hard to overestimate the dominant influence of Cirac and Zoller on the many developments since 1994 at the interface of quantum optics, quantum information, and quantum many-body physics, but to avoid boring you I will mention only one more tremendously seminal paper: with co-authors, Cirac and Zoller proposed using ultracold atomic gases in optical lattices to explore correlated quantum matter and quantum phase transitions, an idea that has energized and transformed experimental atomic physics.
Ignacio and Peter have written over 70 papers together, many of them now classics. Though they don’t collaborate with one another nearly as often as they used to, both continue to produce highly original papers at a staggering pace.
Ignacio and Peter are both exceptionally nice people, each with hardly a shred of arrogance. Yet both are also blessed with supreme (and very well justified) self-confidence as well as unbounded ambition. Perhaps their intellectual fearlessness, as much as extraordinary ability, has enabled them to exert such a deep influence over such a broad swath of physics.
Congratulations, Ignacio and Peter!
[Update: In an earlier version of this post I said that Peter Zoller visited Caltech in "late fall of 1994." I checked my notebook --- it was actually January 9-10, 1995.]