University of Calgary

Extending the reach

UToday HomeJanuary 15, 2013

Wolfgang Tittel and colleagues have received funding from DARPA to overcome the distance barrier in quantum distribution. Photo by Riley BrandtWolfgang Tittel and colleagues have received funding from DARPA to overcome the distance barrier in quantum distribution. Photo by Riley BrandtResearchers in the Institute for Quantum Science and Technology in the Faculty of Science are part of an international team to receive funding from a U.S. agency to develop quantum repeaters — technology that would improve secure, high-rate, long-distance quantum communications.

Quantum communications encodes information in entangled states of photons, making it impossible for people to listen in as the information is distributed.

Currently, information can be encoded and send as far as about 100 km before the system breaks down, says Wolfgang Tittel, associate professor in physics and astronomy and AITF Industrial Research Chair in Quantum Cryptography and Communication.

“For longer distances, we have to break down the long link into many short pieces and use entangled photons between the shorter links,” says Tittel. “We store them at the end points and if we have managed to distribute and store entangled photons at the end points of neighbouring short links, we can extend the entanglements to larger distances by merging entanglements between two short links into one. This is called entanglement swapping.”

The $500,000 funding for the University of Calgary piece of the project comes from the Defense Advanced Research Projects Agency (DARPA), a U.S. organization established in 1958 — the year after the Soviet Union launched Sputnik, the first satellite.

DARPA’s mandate is to “prevent strategic surprise from negatively impacting U.S. national security and create strategic surprise for U.S. adversaries by maintaining the technological superiority of the U.S. military.”

DARPA is funding seven different teams of researchers to try to develop methods to communicate quantum information from 1,000 to 10,000 km.

“The end goal is the same, but the approaches are very different, says Christoph Simon, associate professor in physics and astronomy in the Faculty of Science, who is part of the project. “Right now, DARPA has assembled all these teams that have different approaches to solve the same problem. Everybody has proposed a different way of overcoming the current distance barrier in quantum distribution.”

Tittel says the research, which will run for three years, involves “a lot of things that haven’t been shown yet.”