New Achievements in Fiber Optic Communication: Scientists Developing Quantum Enhanced Receivers

2024-03-07

Fiber optic is an important carrier for high-speed and long-distance communication. However, with the continuous exponential growth of Internet traffic, researchers recently issued a warning of capacity contraction. In the latest issue of AVS Quantum Science published by AIP, researchers from the National Institute of Standards and Technology in the United States and the University of Maryland demonstrated the crucial role of quantum enhanced receivers in addressing this challenge.

Scientists have developed a method based on quantum physical properties to enhance receivers, which significantly improves network performance while reducing error bit rate (EBR) and energy consumption. Fiber optic technology relies on receivers to detect optical signals and convert them into electrical signals. The traditional detection process mainly generates "shot noise" due to random light fluctuations, which reduces detection capability and increases EBR.

To adapt to this problem, when pulsating light becomes weaker along the fiber optic cable, the signal must be continuously amplified, but maintaining sufficient amplification is limited when the signal becomes almost imperceptible. Experimental results have shown that quantum enhanced receivers that can process up to two bits of classical information and overcome scattering noise can improve detection accuracy in laboratory environments. In these and other quantum receivers, an independent reference beam with single photon detection feedback is used, so the reference pulse will ultimately cancel out the input signal to eliminate scattering noise.

However, the researchers' enhanced receiver can decode up to four bits per pulse because it performs better in distinguishing different input states. In order to achieve more effective detection, they developed a modulation method and implemented a feedback algorithm that utilizes the accurate time of single photon detection. Nevertheless, no measurement is flawless, but the new "overall" design of communication systems on average produces more and more accurate results.

The author of this study, Sergey Polyakov, stated, "We investigated communication theory and experimental techniques of quantum receivers, and proposed a practical telecommunications protocol that maximizes the advantages of quantum measurement.". Through our protocol, because we want the input signal to contain as few photons as possible, we maximize the opportunity for the reference pulse to update to the correct state after the first photon detection. Therefore, at the end of the measurement, EBR is minimized.

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