In 1997, I had some disposable funding as part of a quantum computing project, and decided to seize the opportunity to bring an interesting visitor to Caltech. But whom to invite? Chris Fuchs, then a postdoc at Caltech who seemed to know everybody working on quantum computing, reported that Richard Jozsa, while attending a conference in Japan, had met a remarkable Russian from the Landau Institute named Alexei Kitaev.
Responding to this tip, I found a paper by this Kitaev fellow on the arXiv … and was amazed. Later, Alexei told me the story behind this paper. When Peter Shor discovered the efficient algorithm for factoring numbers on a quantum computer in 1994, Alexei heard rumors about the discovery but was unable to attain a copy of Shor’s paper. So he independently invented his own algorithm, which was in some ways similar to Shor’s, but solved a more general problem!
From reading this paper, I was confident that Kitaev would be an interesting visitor. Having learned (again through Chris) that Charlie Bennett and David DiVincenzo were also interested in meeting Kitaev, we arranged to co-sponsor his trip from Russia, with Kitaev splitting his time in the US between IBM and Caltech.
My expectations were high, but not nearly high enough. On his very first day at Caltech, Kitaev told me to call him “Alyosha” (which I later learned should be spelled “Alesha”), and started explaining one of his most marvelous ideas — using non-abelian anyons for fault-tolerant quantum computing. At that time, non-abelian anyons and fault-tolerant quantum computing were two different topics that I already knew a lot about and found very interesting. Yet it had never occurred to me that these two topics were at all related! By the end of the day I understood the connection and I was hooked.
Over coffee at the Red Door Cafe that afternoon, we bonded over our shared admiration for a visionary paper by Greg Moore and Nick Read about non-abelian anyons in fractional quantum Hall systems, though neither of us fully understood the paper (and I still don’t). Maybe, we mused together, non-abelian anyons are not just a theorist’s dream … It was the beginning of a beautiful friendship.
Kitaev’s idea was simple, obvious, and beautiful (the great ideas are obvious in retrospect, but only in retrospect). Anyons are exotic localized particles in a two-dimensional medium. Kitaev understood that a system supporting anyons has many distinct quantum states with nearly the same energy, yet all of these states look essentially identical when we observe their local properties. That’s just the feature that a quantum system should have for its quantum state to be well protected against the damaging effects of noise. Furthermore, we can process the quantum information stored in this manifold of degenerate states by exchanging the positions of the anyons, thereby operating an intrinsically robust quantum computer. We’ll go more deeply into the status of this idea, and its prospects for experimental realization, in later posts.
While Alexei Kitaev was studying physics at the Moscow Institute for Physics and Technology in the mid-1980s, another physics student named Yuri Milner was studying at nearby Moscow State University. Yet they never met until Yuri called to inform Alexei that he had been selected as a recipient of the newly established Fundamental Physics Prize.Yuri hopes that this prize will draw greater attention to the excitement and value of basic science, and inspire young people to pursue scientific careers.
All of this year’s recipients are brilliant scientists with spectacular accomplishments. Congratulations to them all, but especially, congratulations Alesha!