Researchers at Qunnect successfully transmitted thousands of entangled photons over a commercial fiber-optic line in New York City, demonstrating the potential for using existing infrastructure for quantum encryption and computing. The team employed polarization entanglement, creating photons with wavelengths compatible with the fiber network. By transmitting non-entangled photons alongside the entangled ones, they were able to compensate for any polarization shifts, achieving an uptime of nearly 100% with approximately 20,000 entangled photons transmitted per second. This proof-of-concept showcases the possibility of utilizing existing fibers without upgrades for quantum computing and encryption applications.
Source: https://hackaday.com/2024/08/14/entangled-photons-maintained-using-existing-fiber-under-nycs-streets/