Years ago, Barclay Jermain Professor of Natural Philosophy William Wootters was giving a talk at the University of Montreal. Having been invited to speak on any subject in the realm of physics, Wootters of course selected that which most intrigued him: quantum information. He had just co-written a paper exploring whether one could get more information from two different quantum particles if they were brought together and allowed to interact or were kept separate. Once he had finished speaking, a hand went up in the audience. “Is there any way,” began the questioner, “that you could do the same measurements without bringing the particles together? Could you use entanglement?” Wootters didn’t know the answer, but he was definitely intrigued. As he explained to me during our afternoon interview, “Anyone who is not bothered by quantum mechanics has not understood it.”
What happened next, Wootters recounted, was that he, the audience member that had raised his hand and a couple of other attendees spent the rest of the day tackling the question. Present along with Wootters at the conference were colleagues Richard Jozsa, Charles Bennett, Giles Brassard, Claude Crepeau and Asher Peres. This handful of scientists then went on to co-write an extremely successful paper published in 1993 on the transfer of quantum information, titled “Teleporting an Unknown Quantum State via Dual Classical and EPR Channels.” Nine years later, the incredible academic success of their paper has prompted Thomson Reuters to name them Citation Laureates, indicating that they rank in the top 0.1 percent in their field in terms of citation impact.
The paper explores the idea of quantum teleportation. Say you have a particle with a certain, very specific quantum state, and want to transfer that state into another particle a particular distance away – how would you go about doing that? In classical physics, you could simply take the necessary measurements about the particle, broadcast the information to the desired location and have the particle reconstructed. Quantum physics is much more complicated, however; such simple solutions can’t work. A foundational component of quantum physics is the uncertainty principle, which states that the more a subject is measured or observed, the more it is disturbed by said measurement or observation; there is much that we cannot know about the subject as any attempt to record information destroys said information. “With quantum mechanics, then,” Wootters explained to me. “We can’t take the approach of measuring and copying – there would be no information left to copy.”
The remedy to this conundrum, as proposed by Wootters and his colleagues, is to manipulate the relationship between two entangled particles. Entanglement is a quantum mechanical correlation between two particles, made even more interesting in that neither of the particles possesses a complete quantum description by itself. Entangled particles, which usually come from the same source, don’t have to be touching each other. In fact, experiments have been conducted with entangled particles many kilometers away from each other. This makes entanglement a logical option to explore when looking at the communication of quantum information across long distances.
Basically, one of the entangled particles is allowed to interact with the particle whose quantum information is to be transferred. The relationship between the two particles – rather than the details of either individual particle – is then measured. A process of quantum “teleportation” then occurs; if executed correctly, this phenomenon can actually copy the quantum properties of the first particle to the particle on the other side of the entanglement.
When asked why he thinks his paper was so well-received, Wootters humbly joked, “Because we chose such a good name for it!” Indeed, “quantum teleportation” is catchy, curiously reminiscent of many science fiction movies and full of punch. The real reason for the paper’s success, however, lies in its implications. Quantum information is so efficient that an effective quantum information computer, were it to be built, would greatly expand the boundaries of our current technological capacity. Quantum teleportation, then, would allow these quantum computers to be linked in a sort of “quantum Internet” that could theoretically cross giant distances. Indeed, a team in the Canary Islands managed to teleport quantum information from one island to another (a distance of over 143 kilometers) and is planning to send such information to a satellite over a much greater distance. And to think: it was the College’s own Wootters and his colleagues that laid the skeleton for all this new experimentation and all these new scientific possibilities.
What’s next for this international group of scientists and for Williams’ resident physics professor? Well, if the Thomson Reuters prediction is any indication, perhaps, a Nobel nod. In the words of David Pendlebury, one of the Thomson Reuters analysts: “Our Citation Laureates have made such important contributions to science that we believe them to be peers of the Nobel Prize winners in every way; they simply have yet to win.”