National University of Singapore and the Centre for Quantum Technologies Entangling Photons for Cybersecurity. New methods for photon wavelength production show promise in sending entangled photons through common commercial fiber optics networks.
Singapore. Excerpts: “The technique works by carefully designing the photon source to create pairs of light particles with colors either side of a known feature of optical fiber called the ‘zero-dispersion wavelength’. Normally, in optical fibers bluer light would arrive faster than redder light, spreading out the photons’ arrival times. Working around the zero-dispersion point makes it possible to match the speeds through the photons’ time-energy entanglement. Then the timing is preserved.
Associate Professor Alexander Ling, a Principal Investigator at CQT, led this work for the NUS-Singtel lab. He said, “Before these results, it was not known if the multi-segment nature of deployed fiber would enable high precision dispersion cancellation, because the segments don’t generally have identical zero dispersion wavelengths.” The paper’s co-authors also include CQT’s Shi Yicheng, Poh Hou Shun and Christian Kurtsiefer.
In showing it can work, the team boosts expectations for QKD [quantum key distribution] over commercial fiber. The entangled photons could find other applications, too. For example, the photons in each pair are created within femtoseconds of each other. Their coordinated arrival times might synchronize clocks for time-critical operations such as financial trading.”