The observation of genuine three-photon interference, conducted independently by a team of researchers at IQC and the University of Oxford, has been named one of the Top Ten Breakthroughs of 2017 by Physics World magazine.
Each year, editors at Physics World select the top breakthroughs based on the following criteria:
- fundamental importance of research;
- significant advance in knowledge;
- strong connection between theory and experiment; and
- of general interest to all physicists.
The IQC experiment was published earlier this year in Physical Review Letters describing how researchers experimentally passed three photons, which are entangled in their energy and times, through separate interferometers. This enabled them to observe genuine three-photon interference for the first time.
The result provides important foundational insights into multi-particle interference, and could lead to exciting applications in quantum communication and cryptography. For example, imagine a trio of people who each have to use their thumbprint to unlock a safe. One or two of those people cannot secretly open the safe, because the third person is necessary.
The work builds on previous research by IQC faculty members in the Department of Physics & Astronomy, Thomas Jennewein, and Canada Research Chair in Optical Quantum Technology, Kevin Resch. They demonstrated the first direct generation of photon triplets in 2010, and three-photon energy-time entanglement in 2012. While energy-time entanglement is difficult to detect experimentally, the researchers overcame the obstacles in the 2017 work and were able to observe the three-photon interference signature very clearly.
The experiment is a result of a collaboration led by Jennewein between the University of Waterloo (Sascha Agne, Jeongwan Jin, Resch, Jeff Salvail, Evan Meyer-Scott), the University of Innsbruck (former IQC member Gregor Weihs and Thomas Kauten) and Université de Moncton (former IQC student Deny Hamel).
Physics World is the membership magazine of the Institute of Physics, one of the largest physical societies in the world.