Quantum system detects ultra-faint communications signals

September 29, 2020 //By Rich Pell
Quantum system detects ultra-faint communications signals
Researchers at the National Institute of Standards and Technology (NIST) say they have developed and demonstrated a quantum measurement system that can detect even the faintest of communications signals.

The system, say the researchers, could dramatically increase the performance of communications networks while enabling record-low error rates - potentially decreasing the total amount of energy required for state-of-the-art networks by a factor of 10 to 100. The proof-of-principle system consists of a novel receiver and corresponding signal-processing technique that, unlike the methods used in today’s networks, are entirely based on the properties of quantum physics and thereby capable of handling even extremely weak signals with pulses that carry many bits of data.

"We built the communication test bed using off-the-shelf components to demonstrate that quantum-measurement-enabled communication can potentially be scaled up for widespread commercial use," says Ivan Burenkov, a physicist at the Joint Quantum Institute, a research partnership between NIST and the University of Maryland. "Our effort shows that quantum measurements offer valuable, heretofore unforeseen advantages for telecommunications leading to revolutionary improvements in channel bandwidth and energy efficiency."

Modern communications systems convert information into a laser-generated stream of digital light pulses in which information is encoded - in the form of changes to the properties of the light waves - for transfer and then decoded when it reaches the receiver. The train of pulses grows fainter as it travels along transmission channels, and conventional electronic technology for receiving and decoding data has reached the limit of its ability to precisely detect the information in such attenuated signals.

The signal pulse can dwindle until it is as weak as a few photons - or even less than one on average. At that point, inevitable random quantum fluctuations - called "shot noise" - make accurate reception impossible by normal ("classical," as opposed to quantum) technology because the uncertainty caused by the noise makes up such a large part of the diminished signal. As a result, existing systems must amplify the signals repeatedly along the transmission line, at considerable energy cost, keeping them strong enough to detect reliably.

The NIST system, say

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