The new system detects signs of ambiguous communication using the principles of quantum physics.

Researchers at the National Institute of Standards and Technology (GIS) (NISIT) have demonstrated a system that can dramatically increase the performance of a communication network while failing to detect signals enables record-low error rates. For a sophisticated network by a factor of 10 to 100.

The proof-principle system has a novel receiver and corresponding signal-processing technology that, unlike the methods used in today’s networks, is based entirely on the properties of quantum physics and is capable of handling extremely weak signals with pulses. Many bits of information.

“We created a communication test bed using -f-the-shelf components to demonstrate that quantum-scalable-capable-communication could potentially be expanded for wider commercial use,” said Ivan Burenkov, a physicist at the Joint Quantum Institute. NIST and University of Maryland. Burenkov and colleagues report results Physical Review X Quantum. “Our effort demonstrates that quantum measurement is another valuable, unforeseen advantage for previous telecommunications that has led to radical improvements in channel bandwidth and energy efficiency.”

Modern communications systems work by converting information into a laser-generated stream of digital light pulses in which information is encoded – in the form of a change in the properties of light waves – for transfer and then decoded when it reaches the receiver. The train of pulses increases figuratively when traveling with transmission channels, and traditional electronic technology for receiving and decoding data has reached the limit of its ability to accurately detect information in such specialized signals.

The signal can pulse until it is as weak as a few photons or even below average. At the time, the inevitable random quantum fluctuations, known as “shot-sound”, made accurate reception impossible by common (as opposed to “classical,” quantum) techniques, as the uncertainty caused by the noise made up so much of the declining signal. As a result, existing systems must amplify frequent signals along the transmission line, at a significant cost, to keep them strong enough to detect reliably.

The NIST team’s system can eliminate the need for amplifiers because it can process extremely weak signal pulses reliably: “The overall energy requirement that hinders the development of networks becomes a fundamental factor,” said Sergei, a senior scientist at NIST. Team. “The goal is to reduce the need for lasers, amplifiers, detectors, and auxiliary devices to reliably transmit the required amount of long-distance radiation over long distances. Communicate information – an essential step toward that goal. “

To increase the rate at which information can be transmitted, network researchers are looking for ways to encode more information per pulse using the additional properties of the light wave. So a single laser light pulse, depending on how it was originally designed for transmission, can carry a lot of data. To improve the accuracy of the probe, quantum-enhanced receivers can be fitted to classical network systems. To date, those hybrid compounds can process up to two bits per pulse. The NISIT quantum system uses as many as 16 different laser pulses to encode four bits.

To demonstrate that capability, NIST researchers created a stupid laser pulse input compared to a significantly weaker traditional network signal, with an average number of photons per pulse averaging 0.5 to 20 (although photons are whole particles, meaning less than one. Are not).

After generating this input signal, NIST researchers take advantage of its wavelength properties, such as interference, until it rotates the detector as a photon (particle). In the field of quantum physics, light can act as either particles (photons) or waves with properties such as frequency and phase (relative position of wave peaks).

Inside the receiver, the pulse train of the input signal connects (interferes) with a separate, adjustable reference laser beam, which controls the frequency and phase of the combined light flux. It is extremely difficult to read the various encoded states in such a vague signal. The NIST system is therefore designed to measure the properties of the entire signal pulse by trying to match the properties of the reference laser. Researchers achieve this by a series of sequential measurements of the signal, each of which increases the probability of an accurate match.

This is done by adjusting the frequency and phase of the reference pulse so that it destructively interferes with the signal when the beam connects to the splitter, completely canceling the signal so that no photons can be detected. In this scheme, shot noise is not a factor: there is no uncertainty of total cancellation.

Thus, counterintuitively, no photons reach a perfectly accurate measurement detector. If the reference pulse has the wrong frequency, the photon can reach the detector. The receiver uses photon detection time to predict the most probable signal frequency and adjusts the frequency of the reference pulse accordingly. If that prediction is still incorrect, the subsequent photon detection time results in a more accurate prediction based on both photon detection times, and so on.

“Once the signal contacts the reference beam, the probability of finding the photon changes over time,” Burenkov said, “and as a result the photon detection type contains information about the input state. We use that information to increase the chance of accurately predicting later. The very first photon discovery.

“Our communication protocol is designed to provide different temporal profiles for different combinations of signal and reference light. The search time can then be used to differentiate between input states with some certainty. The certainty may initially be very low, but it has improved throughout the measurement. We want to switch the reference pulse to the right position after the very first photon probe because the signal has only a few photons, and the longer we measure the signal with the correct reference, the better our confidence.

Polikov discussed possible applications. The future exponential growth of the Internet, he said, would require a change in the technology behind communication. “Quantum measurement could be this new technology. We’ve demonstrated a record low error rate with a new quantum receiver connected to the maximum encoding protocol. Our approach could significantly reduce the gap for telecommunications.”