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Researchers at the University of Waterloo’s Institute for Quantum Computing (IQC) have combined two Nobel prize-winning research concepts to advance the field of quantum communication. By efficiently producing nearly perfect entangled photon pairs from quantum dot sources, the IQC research team aims to optimize the process for creating entangled photons, which have a wide variety of applications, including secure communications. Entangled photons are particles of light that remain connected, even across large distances, and the 2022 Nobel Prize in Physics recognized experiments on this topic. Combining entanglement with quantum dots, a technology recognized with the Nobel Prize in Chemistry in 2023, the researchers hope to extend the reach of secure quantum communication to a global scale or link remote quantum computers.

Dr. Michael Reimer, professor at IQC and Waterloo’s Department of Electrical and Computer Engineering, explains the importance of achieving a high degree of entanglement and efficiency for applications such as quantum key distribution or quantum repeaters. Previous experiments have only measured either near-perfect entanglement or high efficiency, but the IQC research team has successfully achieved both requirements with their quantum dot source. By embedding semiconductor quantum dots into a nanowire, the researchers have created a source that produces near-perfect entangled photons 65 times more efficiently than previous work. This new source, developed in collaboration with the National Research Council of Canada in Ottawa, can be excited with lasers to generate entangled pairs on command, and high-resolution single photon detectors are used to boost the degree of entanglement.

PhD student Matteo Pennacchietti, also from IQC and Waterloo’s Department of Electrical and Computer Engineering, discusses how they overcame historical challenges with quantum dot systems, specifically the problem of fine structure splitting that causes an entangled state to oscillate over time. By combining quantum dots with a fast and precise detection system, the researchers can accurately measure the entanglement at each point during the oscillations, ensuring near-perfect entanglement is achieved. This breakthrough has significant implications for future communications applications, and the researchers have worked with other IQC faculty members to demonstrate the potential of their quantum dot entanglement source in a simulated secure communications method known as quantum key distribution.

Dr. Norbert Lütkenhaus and Dr. Thomas Jennewein, both IQC faculty members and professors in Waterloo’s Department of Physics and Astronomy, collaborated with Reimer and Pennacchietti to showcase the capabilities of the new quantum dot entanglement source. By simulating quantum key distribution, a method for secure communications, the researchers have proven that their quantum dot source holds great promise for the future of secure quantum communications. The ability to create near-perfect entangled photons efficiently using quantum dots opens up new possibilities for extending the distance of secure quantum communication or linking remote quantum computers. With their innovative approach and successful experiments, the IQC team is contributing to the advancement of quantum communication technologies and bringing together Nobel prize-winning research concepts in a practical and impactful way.

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