Quantum networks are a revolutionary technology that holds the promise of secure communication and ultra-fast computing capabilities. However, bringing quantum networks into the marketplace is not without its challenges. Engineers face the fragility of entangled states in fiber cables and the need to ensure efficient signal delivery. One company, Qunnect Inc. in Brooklyn, New York, has made significant progress in this area by operating a quantum network under the streets of New York City.
The team at Qunnect used a leased 34-kilometer-long fiber circuit, which they named the GothamQ loop, to test their prototype network. By utilizing polarization-entangled photons, they were able to achieve an uptime of 99.84% over 15 continuous days. The team transmitted entangled photon pairs at a rate of about 20,000 per second, with a compensation fidelity of 99%. Even at a higher rate of half a million entangled photon pairs per second, the fidelity remained around 90%.
Polarization plays a crucial role in quantum networks, where entangled photons are used to transmit information securely. Polarized photons have a specific direction for their electric field, making them easy to create, manipulate, and measure. This property has enabled the development of large-scale quantum repeaters, distributed quantum computing, and quantum sensing networks. Moreover, the study of quantum entanglement, which won the 2022 Nobel Prize in Physics, has opened up new possibilities for quantum technology.
One of the challenges faced by the Qunnect team was polarization drift, which was both wavelength and time-dependent. To combat this issue, they designed and built equipment for active compensation at the same wavelengths. By sending classical photon pairs down the fiber to measure polarization drift, the team was able to correct the polarization of the entangled pairs using automated polarization compensation (APC) devices. This automated process was essential for maintaining the stability of the network over long distances.
Future of Quantum Networks
The success of Qunnect’s GothamQ loop demonstration marks a significant step towards a fully automated entanglement network, necessary for the development of a quantum internet. The team’s commitment to making their technology accessible by creating rack-mounted equipment, known as Qu-Val, shows their dedication to advancing quantum networking technologies. As quantum networks continue to evolve, overcoming challenges such as polarization drift will be crucial for their widespread adoption.
The journey towards incorporating quantum networks into our daily lives is filled with obstacles and breakthroughs. The work done by companies like Qunnect represents a crucial step in overcoming the fragility of entangled states in fiber cables and ensuring efficient signal delivery. With further research and technological advancements, quantum networks have the potential to revolutionize communication and computing as we know it.
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