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Research Highlight

Researchers Reach Quantum Networking Milestone in Real-World Environment

The Science
Researchers from ORNL, Stanford University, and Purdue University developed and demonstrated a novel, fully functional quantum local area network (QLAN). The team distributed entanglement from a photon source to three geographically isolated systems—Alice, Bob, and Charlie—which were located in separate buildings on ORNL’s campus. The team made the first demonstration of remote state preparation, a quantum communications protocol, on an optical network.

The Impact
The new QLAN is a step towards the connection of future quantum computers and sensors to realize the full potential of these next-generation technologies. The team anticipates that small upgrades to the QLAN, including adding more nodes and nesting wavelength-selective switches together, would form quantum versions of interconnected networks, helping establish the highly anticipated quantum internet. Additionally, the researchers’ findings could be applied to improve other detection techniques, such as those used to seek evidence of dark matter. 

Team Members: Muneer Alshowkan, Brian P. Williams, Philip G. Evans, Nageswara S.V. Rao, Claire E. Marvinney, Yun-Yi Pai, Benjamin J. Lawrie, Nicholas A. Peters, Joseph M. Lukens (all of ORNL), Emma M. Simmerman (Stanford University), Hsuan-Hao Lu, Navin B. Lingaraju, Andrew M. Weiner (all of Purdue University)

The researchers used remote state preparation, which harnesses entanglement and classical communications to encode information by measuring one half of an entangled photon pair and effectively converting the other half to the preferred quantum state. They applied this technique across all the paired links in the QLAN—a feat not previously accomplished on a network—and demonstrated the scalability of entanglement-based quantum communications. Because quantum networks are incompatible with amplifiers and other classical signal boosting resources, which interfere with the quantum correlations shared by entangled photons, the team incorporated flexible grid bandwidth provisioning, which uses wavelength-selective switches to allocate and reallocate quantum resources to network users without disconnecting the QLAN. This technique provides a type of build-in fault tolerance through which network operators can respond to an unanticipated event, such as a broken fiber, by rerouting traffic to other areas without disrupting the network’s speed or compromising security protocols. Using a GPS antenna, the researchers synchronized GPS-based clocks in each laboratory within a few nanoseconds to ensure they would not drift apart during the experiment.

Acknowledgement of Support
This work was performed in part at ORNL, operated by UT-Battelle for the U.S. Department of Energy under contract no. DE-AC05-00OR22725. Funding was provided by DOE’s Office of Science, Office of Advanced Scientific Computing Research, through the Early Career Research Program and Transparent Optical Quantum Networks for Distributed Science Program. Members of the team were supported by the Quantum Information Science and Engineering Network through the National Science Foundation, DOE’s Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, and the Intelligence Community Postdoctoral Research Fellowship Program at ORNL administered by the Oak Ridge Institute for Science and Education through an interagency agreement between DOE and the Office of the Director of National Intelligence.