Unlocking high-dimensional quantum optics
Tuesday, February 15, 2022
Collaboration is key at the Institute for Quantum Computing (IQC). IQC researchers are working together towards unlocking high-dimensional quantum optics. They are advancing fundamental research with future applications for quantum communications and computing. Building off earlier research, a group of IQC researchers measured the correlation of polarization-entangled photon pairs using orbital angular momentum (OAM) lattices.
OAM, a property of light, refers to the twisting of a particle. The polarization of light offers access to only a limited number of states, but OAM allows access a vast number of states. The team used both polarization and OAM to combine the advantages of both. Expanding the number of accessible states with OAM, while using the controllable nature of polarization, moves the research towards one of the big goals of quantum optics: high-dimensional entanglement.
An earlier study led by Dusan Sarenac, a research associate at IQC, investigated OAM lattices with neutrons. Following the success of that first experiment with neutrons, the team posited that the same may also be measured with photons.
“On the surface, neutrons and photons don’t seem to have a lot in common, but when you dig in, they do. Sometimes the applications of one end up being interesting for the other as well,” said Andrew Cameron, PhD student with the Department of Physics and Astronomy and IQC member.
The IQC advantage is that theorists and experimentalists work together. It is a collaborative and interdisciplinary approach to research. Each researcher brought their unique expertise to each step of the experiment from design to implementation in the Quantum Optics and Quantum Information lab.
This team first demonstrated a Talbot effect of OAM lattices with single photons. This latest investigation introduces multi-particle entanglement, not yet possible with neutrons.
“We published our first report about what happens if these kind of lattice states propagate. They transform and interfere with themselves as they propagate which is called the Talbot effect,” said Cameron. “The second step was applying the lattice transformation to one of the photons to produce correlations between the OAM of one photon and the polarization of its entangled partner.”
Entanglement is when two objects or particles have such a strong correlation that the properties of one cannot be described without considering the properties of other. Using photon pairs with polarization entanglement, the team passed one photon from each pair through a prism to manipulate its OAM. The team then measured the polarization of one entangled photon to determine the OAM lattice of its photon partner. The experiment showed a strong correlation between photon pairs, indicating entanglement.
Future work is to study the lattices with more prism pairs to expand the number of accessible OAM states. Unlocking high-dimensional quantum optics would expand quantum communication protocols to be more robust and encode more information.
Kevin Resch, principal investigator led this research in collaboration with IQC’s Transformative Quantum Technologies (TQT) led by professor David Cory. This research was supported in part by the Canada First Research Excellence Fund through TQT.
The study Remote state preparation of single-photon orbital-angular-momentum lattices by Andrew Cameron, Sandra Cheng, Sacha Schwarz, Connor Kapahi, Dusan Sarenac, Michael Grabowecky, David Cory, Thomas Jennewein, Dmitry Pushin, and Kevin Resch was published in Physical Review A on November 22, 2021.