An international team from Wits University and ICFO demonstrates the teleportation-like transport of patterns of light – this is the first approach that can transport images across a network without physically sending the image, and a crucial step towards realising a quantum network for high-dimensional entangled states. So, quantum optics allow us to increase the alphabet and to securely describe more complex systems in a single shot, such as a unique fingerprint or a face.

“Traditionally, two communicating parties physically send the information from one to the other, even in the quantum realm,” says Andrew Forbes from Wits University. “Now, it is possible to teleport information so that it never physically travels across the connection.” Unfortunately, teleportation has so far only been demonstrated with three dimensional states therefore needing additional entangled photons to reach higher dimensions. In this research, the team performed the first experimental demonstration of the quantum transport of high-dimensional states with just two entangled photons as a quantum resource, which resulted in the information appearing to be teleported from the sender to the receiver.

To make the advance, the team used a nonlinear optical detector that circumvents the need for additional photons, yet works for any pattern that needs to be sent. They report a new state-of-the-art of 15 dimensions, with the scheme scalable to even higher dimensions, paving the way for quantum network connections with high information capacity. “This protocol has all the hallmarks of teleportation except for one essential ingredient: it requires a bright laser beam to make the nonlinear detector efficient, so that the sender could know what is to be sent, but doesn’t need to know,” explains Forbes. “In this sense, it is not strictly teleportation, but could be in the future if the nonlinear detector could be made more efficient.” Even as it stands now, it opens a new pathway for connecting quantum networks, ushering in nonlinear quantum optics as a resource.

“We hope that this experiment showing the feasibility of the process motivates further advances in the nonlinear optics community through pushing the limits towards a full quantum implementation,” says Adam Vallés from ICFO in Barcelona. “We have to be cautious now, as this configuration could not prevent a cheating sender from keeping better copies of the information to be teleported, which means we could end up with many Mr Spock clones in the Star Trek world if that is what Scotty wanted. From a practical point of view, the configuration that we currently demonstrate can already be used to establish a high-dimensional secure channel for quantum communications between two parties, provided that the protocol does not need to be fed with single photons, as would be the case for quantum repeaters.”

Vallés adds: “Performing such proof-of-concept experiments with currently available technology has been an interesting journey, and we have Bereneice Sephton from Wits to thank for her determination and the comprehensive skills set needed to tame such an experimental beast. This is a true laboratory endeavour for which she should be lauded.” Forbes echoes the sentiment: “This was an heroic experiment and Bereneice Sephton must be recognized as she is the one who got the system to work and performed the key experiments.” The team plan to continue working in this direction, with the next step focusing on quantum transport across an optical fiber network. (Source: Wits U.)

Reference: B. Sephton et al.: Quantum transport of high-dimensional spatial information with a nonlinear detector, Nat. Commun. 14, 8243 (2023); DOI: 10.1038/s41467-023-43949-x

Link: Structured Light Laboratory, School of Physics, University of the Witwatersrand, Wits, South Africa