The introduction of quantum networks into the marketplace has always been hindered by the fragility of entangled states in a fiber cable and the efficiency of signal delivery. Scientists at Qunnect Inc. in Brooklyn, New York, have made significant progress by successfully operating a quantum network under the streets of New York City. Previous attempts to transmit entangled photons were plagued by noise and polarization drift, making it challenging for entanglement to survive in a long-term stable network.
The team at Qunnect designed a prototype network using a leased 34-kilometer-long fiber circuit known as the GothamQ loop. By utilizing polarization-entangled photons, they were able to achieve an impressive uptime of 99.84% over 15 continuous days. The compensation fidelity for entangled photon pairs was maintained at 99% while being transmitted at a rate of approximately 20,000 pairs per second. Even at a higher transmission rate of half a million entangled photon pairs per second, the fidelity remained at nearly 90%.
Polarization plays a crucial role in quantum networks, as it determines the direction of an electric field within a photon. Polarized photons are easy to create, manipulate, and measure, making them valuable for various quantum applications. The use of polarization-entangled photons has enabled the development of large-scale quantum repeaters, distributed quantum computing, and distributed quantum sensing networks.
Quantum entanglement, the phenomenon where particles within a quantum state are interconnected regardless of distance, has been at the forefront of recent scientific research. The Qunnect team utilized infrared and near-infrared photons to create entangled dual-colored photon pairs, compatible with rubidium atomic systems used in quantum memories and processors.
One of the major challenges faced by the Qunnect team was polarization drift, which was found to be both wavelength and time-dependent. To compensate for this drift, they designed and built equipment for active compensation at specific wavelengths. By sending classical photons down the fiber and measuring their polarization drift at different distances, the team was able to develop automated polarization compensation devices to correct for disturbances.
The success of the GothamQ loop demonstration showcased progress towards a fully automated practical entanglement network essential for the development of a quantum internet. The hands-off operation, high uptime percentage, and durability of the network highlight the potential of quantum networks in real-world applications. The team at Qunnect continues to improve their equipment, with all parts now rack-mounted for universal use, under the name Qu-Val.
The advancements made by Qunnect Inc. in operating a stable and efficient quantum network pave the way for the future of quantum communication. By overcoming the fragility of entangled states and addressing polarization drift, engineers are one step closer to realizing the full potential of quantum networks in revolutionizing communication and computing technology.
Leave a Reply