The foundations of quantum networks are being consolidated today. Quantum computers are not the only devices designed to harness the properties of quantum mechanics, as communications can also exploit them. This possibility paves the way for the deployment of large-scale quantum communications infrastructure that would promise to transfer information instantaneously and with inherent security.
The National Institute of Standards and Technology (NIST) in the United States successfully conducted an experiment in which it transmitted photons through a network of conventional cable 62 kilometres long without losing quantum entanglement. The milestone was particularly significant because it took place in a real-world scenario rather than a protected laboratory environment. Most of the optical fibre cabling used was installed on street poles between NIST facilities and the University of Maryland, exposed to wind, temperature variations and adverse weather conditions.
Yicheng Shi, physicist and researcher at NIST, noted that she and her colleagues were surprised to find that entanglement was preserved even in an extremely noisy environment. The team used a laser as a reference to correct the deviation of the entangled photons, a strategy that proved suitable in a real-world usage scenario. The experiment was published in the Journal of Optical Communications and Networking.
Despite the success, the researchers acknowledged that challenges remain. The transmission speed in this test ranged between 200 and 1,500 entangled photons per second, improvable in a real-world usage scenario. Additionally, the scientists indicated that more efficient software algorithms need to be developed. However, these challenges do not appear insurmountable considering the technological advances made over the past decade.
