F-22 is considered one of the most advanced fighter jets in the world (Reuters)
Chinese media recently reported that China has begun mass production of quantum radar systems, which are believed to be able to detect stealth fighters such as the U.S. F-22 and F-35, which are among the most advanced aircraft in the world. This move may represent a technological leap in the field of electronic warfare.
Traditional radars work by emitting radio waves, which reflect off objects and are interpreted as target location information, similar to how bats use echolocation.
However, quantum radar relies on a completely different physical principle, using single photons instead of radio waves. This allows the radar to detect even the smallest objects with unprecedented precision.
The working principle of traditional radar is to emit radio waves that reflect off objects (Getty Images)
The Most Powerful Fighter Jets in the World
The F-22 fighter jet costs up to $350 million and is one of the most advanced fighter jets in the world. It is equipped with fifth-generation technology, combining supersonic flight, excellent maneuverability, stealth capabilities, and integrated sensors, enabling it to operate in various weather conditions.
This fighter jet was initially designed for air superiority - the control of airspace during military conflicts.
On the other hand, the F-35 stealth fighter jet costs up to $115.5 million and is a multirole fighter jet, also a fifth-generation aircraft. It is capable of performing air-to-air combat, precise ground attacks, and reconnaissance missions.
This fighter jet can switch between different mission roles in a single operation, allowing it to flexibly respond to various combat scenarios.
By comparison, China has the Chengdu (J-20) fighter jet, a fifth-generation multirole fighter developed by the Chengdu Aircraft Industry Group for the Chinese People's Liberation Army Air Force. The cost of this fighter jet is roughly equivalent to that of the F-35 and is considered the most advanced fighter jet currently in China.
In general, fifth-generation fighter jets possess low observability (stealth) characteristics to reduce their radar cross-section. This is mainly achieved through advanced chemical coatings that do not scatter radar waves and aircraft engineering designs that surpass radar detection capabilities.
Additionally, weapons are hidden inside the fuselage, reducing their thermal signature to an extremely low level, making them undetectable by existing infrared radars.
Photons are the basic particles that make up light (Benjamin Yon)
The Mystery of Single Photons
But quantum radar overcomes all these limitations. To understand its precision, we first need to understand photons - the fundamental particles that make up light. When we talk about "single photon detectors," we refer to devices capable of detecting individual light particles - an incredible achievement considering the human eye requires billions of photons per second to clearly see a small desk lamp.
Using a single photon rather than radio waves enables extremely precise detection because the quantum state of a single photon can be tracked very accurately (including phase, polarization, and energy).
The principle of this radar is to convert the weak energy of photons into measurable electrical pulses. When a photon enters the radar system, it triggers a series of precise interactions within the sensitive material of the device, ultimately generating a weak current, which can be interpreted as a "single photon signal."
Quantum entanglement refers to a relationship between two particles regardless of distance (Wikipedia)
Entangled Photons
The uniqueness here lies in the fact that these photons can be produced in pairs of quantum entanglement, meaning that any change in one photon will affect the other, no matter how far apart they are.
Quantum entanglement is an intriguing physical phenomenon where the states of two particles (such as two photons or two electrons) become interdependent, regardless of the spatial distance between them.
If the state of one particle changes, the state of the other particle will also change immediately in a coordinated manner, as if there were an invisible communication between them beyond distance.
To understand this concept, imagine you have a pair of magic dice, one in Cairo, Egypt, and the other in your friend's hands in Tokyo, Japan. You both roll the dice at the same time, and strangely, each time the numbers rolled are the same, even though the dice are just ordinary plastic products that cannot sense anything.
This is how quantum entanglement works in nature: two particles originating from the same source always remain connected. No matter how far apart they are, once the state of one photon is measured, the state of the other can be determined immediately.
In quantum radar, when one of the entangled photons hits an object, the object's properties (such as direction or polarization) change. This change can be precisely detected by the other photon remaining in the radar system.
Therefore, even if the reflected signal strength is less than that of traditional radar, the system can detect the subtle changes caused by stealth aircraft on the photon path.
The F-35 stealth fighter jet costs up to $115.5 million and is a multirole fighter jet (French media)
Four-Channel Detector
According to the website Interesting Engineering, Chinese researchers have developed a "four-channel single photon detector" which is said to have sensitivity sufficient to detect single photons.
This achievement could promote the production of compact, energy-efficient field quantum radars that can be easily deployed on military bases, aircraft, and ships.
Although this concept is fascinating, China has not yet released publicly available scientific data or field test records to confirm that this quantum radar can indeed detect F-22 or F-35 fighter jets in actual combat environments.
Additionally, many scientists question the feasibility of maintaining quantum entanglement over long distances or under changing atmospheric conditions. Quantum entanglement is a very fragile phenomenon that can easily be broken, causing the connection between the two photons to disappear.
Thermal noise and electromagnetic interference can also weaken quantum signals, making their practical application in warfare extremely difficult.
Single photon detectors are used for quantum satellite communications (NASA)
China's Previous Successes
Despite this, China has made significant achievements in the development of single photon detectors. For example, in 2019, scientists from the University of Science and Technology of China successfully developed a single photon detector that can work in harsh space environments.
Space is filled with cosmic radiation and high-energy particles, which can interfere with any optical detector. These particles generate false signals that suggest the presence of false photons.
To overcome this issue, researchers used a double-layer aluminum tantalum metal shield to protect the internal components of the detector. Additionally, the device was cooled to minus 15 degrees Celsius to minimize thermal noise from interfering signals.
The detector successfully reduced the error rate from over 200 times per second to approximately 0.5 times per second. The device was tested on the MISIOS satellite launched by China to test space quantum communication and proved that it could effectively receive single-photon signals from hundreds of kilometers away on Earth.
Of course, this achievement is limited to the field of quantum communication. If the technology in the field of quantum radar is proven to be true, it would completely change the balance of aerial power, as the "stealth" principle relied upon by the United States and its allies since the 1990s might lose its effectiveness.
Starlink satellites (Wikipedia)
China's Attempts
China's efforts to detect stealth fighters continue. For example, in September 2023, a research team from the Chinese People's Liberation Army Air Force announced that they successfully detected an aircraft with a radar cross-section similar to that of the U.S. F-22 and F-35 fighter jets by using electromagnetic waves transmitted by SpaceX's Starlink satellites.
SpaceX, owned by Elon Musk, is known for having the largest low-Earth-orbit satellite network in the world, with more than 6,000 satellites transmitting high-frequency signals to provide high-speed internet services.
In the experiment, the team flew a DJI Phantom 4 Pro small drone with a radar cross-section similar to the two aircraft over the coastal area of Guangdong Province in southern China. Their trajectories and movement patterns were displayed on the radar screen.
Scientists explained that the reason these drones could be detected is because the electromagnetic radiation from a Starlink satellite flying over the Philippines illuminated the drone.
According to the study announced to have been accepted for publication in the Journal of Signal Processing, their radar itself does not emit any radiation but acts as a receiver, receiving electromagnetic signals emitted by communication satellites (such as Starlink satellites) flying above the atmosphere. The drone interfered with the radar signal, thus revealing the drone's presence.
The research team explained that the trail of stealth aircraft can always be detected because they pass through the airspace between satellites and ground receivers in the upper atmosphere. The more satellites there are (which are expected to increase in the future), the easier it becomes to detect such aircraft.
The research team plans to conduct high-altitude flight experiments on real stealth aircraft to verify their findings. Although the radar cross-section of small drones is similar to that of stealth aircraft, these drones fly at low altitudes.
The End of the Stealth Era
Indeed, some experts believe that the era of "stealth" we are familiar with is about to end. This is not only China's effort; emerging technologies are threatening the entire stealth field, such as low-frequency radars that are not affected by the angle of the aircraft and can detect aircraft even with limited accuracy.
Additionally, multi-position radars have seen significant developments, with transmitter and receiver stations separated from each other, making it difficult for aircraft to deceive all directions simultaneously.
Modern infrared tracking systems can now detect the thermal signals of an aircraft's body or engine from a great distance with unprecedented accuracy, without emitting detectable signals themselves.
Certainly, artificial intelligence and data sets add complexity to this scale, as intelligent systems can integrate different signals from radars, civilian antennas, and satellites to create a precise "tracking image" of stealth targets.
Indeed, major military powers, including the Chinese military, have already begun developing the concept of "stealth" and integrating it into new strategies that abandon the "lone wolf" approach to combat. Stealth fighter jets have become nodes in a network that coordinates the operations of aircraft, ships, and missiles.
In this context, artificial intelligence and swarm tactics play a crucial role. Hundreds of small drones (UAVs) can confuse enemy defense systems with their large numbers and diverse flight paths. Therefore, even though they are visible on radar, they still have a certain degree of stealth capability.
Even if the aircraft are detected, advanced jamming and deception techniques can confuse the enemy, preventing radar from locking onto them. This means that although radar can "see" the fighter jet, it is difficult to target it, and it is also hard to continuously monitor its position and speed, making it ineffective to guide air defense weapons.
In the end, the current situation is a long-standing battle between stealth and detection. It is like a game of chess between two teams: one team proposes scientific principles and applies them to technological practice, while the other team finds the loopholes in those principles. The first team solves problems, and the second team identifies the flaws in the solutions, repeating this cycle endlessly.
Sources: Electronic Website
Original: https://www.toutiao.com/article/7569934515477529129/
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