A study conducted by Chinese researchers could expand the detection range of stealth aircraft for quantum-based radars, according to a South China Morning Post website reported on Dec. 15, according to a report in the December 12 issue of the South China Morning Post. In a paper published earlier this month, a team from the University of Science and Technology of China in Hefei, Anhui Province, described their experiments in detail for the first time, showing that weak-value measurements – an emerging Quantum measurement technology – can detect previously unable to detect the signal.
The technique uses very “gentle” methods to repeatedly measure the quantum states of subatomic particles, and may be particularly useful for detection of very weak signals, such as stealthy radar signatures, the report said.
A quantum scientist at the University of Nanjing in Jiangsu province who did not participate in the study cautioned that it was “laboratory results that were not yet ready for immediate field use,” but the quantum scientist added that the study, It is possible “to expand the detection range of quantum radar.” Quantum scientists at the University of Science and Technology of China have created the world’s first quantum satellite, launched in August this year, but also to create the world’s longest ground quantum communication network.
According to the China Electronics Technology Group Corporation, the University of Science and Technology of China researchers also participated in the development of China’s first quantum radar system. Earlier this year, China Electronics Technology Group Corporation announced that China’s quantum radar technology to detect the effective distance of 100 km, is outside the prototype detection range of quantum radar 5 times.
China believes that the stealth aircraft of the United States and its allies pose a major threat to China’s regional interests. Japan last month to receive the first F-35 stealth fighter, in the future, China is likely to be more stealth fighter and bomber surrounded.
It is reported that the quantum radar system produces pairs of photons, in the entangled state of light particles. One of the photons in the photon pair is emitted and the other is left at the radar station. When the target position is locked, some photons are reflected back, and by matching with the entangled photons retained in the radar station, the “identity” of the photon can be confirmed. By measuring the reflected photons, the researchers can calculate the physical properties of the target, such as size, shape, speed and attack angle. However, a major problem with quantum radars is that the number of reflected photons is small and the distance to the target is larger, the smaller the number of reflected photons. The theoretical limit distance is called the shot noise limit, and if this distance is exceeded, the target can not be detected even under the highest quality observation conditions.
In addition to the problem of shot noise limits, photon-borne information may be obscured by subatomic noise generated between photons, which can not be measured reliably, as photons are struck by a projectile like a randomly-launched projectile, Particle is the name. Researchers at the University of Science and Technology of China, led by Prof. Guo Guangcan and Prof. Li Chuanfeng, have announced that they use high-precision quantum weak measurement technology to break through the shot noise limit and achieve precise detection even in very small quantities of photons.
Reported that the technology from quantum physics in a paradox. In the subatomic world, measurement means destruction. The measurement of subatomic particles inevitably destroys its initial quantum state. But in the 1980s, scientists finally found a solution. The weak measurement method does not cause the collapse of the quantum state. Although each weak measurement can only get a small amount of information, but for the same number of particles repeated measurements, we can get on the property of the robust statistics, the correct guess. However, early weak measurement schemes are inefficient. Only a small proportion of the photons in the detection range can be measured and the rest of the photons are discarded.
In recent years, scientists have developed a new method called energy cycle measurement, the photon placed in a special device to cycle, thereby reducing the number of abandoned photons. China University of Science and Technology research team conducted a laser beam deflection measurement test, proved that this method can break through the shot noise limit. Not only did they detect signals with a signal strength less than half the shot noise limit, but they also increased the accuracy by a factor of 1.5.
The professor at Nanjing University says the technology “definitely” can be used in quantum radars. However, a quantum scientist at Tsinghua University doubts the technology’s short-term utility. “So far, I have not heard of any practical applications of weak metrology,” says the quantum scientist who requested anonymity. “Weak measurements are still measurements that inevitably change the state of the measurement object and thus limit the technology The application prospect.
“Weak measurement shows us whether it is true physical observation, or just a mathematical illusion, is still controversial.”
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