The utility of Modern high frequency Radars have become degraded due to innovation in stealth that resulted include unusual shapes that deflect radar waves—like the US B-2 bomber’s “flying wing” design (above)—as well as carbon-based materials and novel paints. China and Russia have since gotten stealth aircraft of their own, but America’s are still better. However, now another technology innovation of Quantum Radar is promising to detect even stealth aircrafts.
Such a Radar could render the $US1 trillion F-35 Joint Strike Fighter program obsolete. Stealth whish had revolutionized the Air power by vastly enhancing the penetration capabilities of aircrafts since they are extremely difficult to detect through conventional radars, is now under threat of quantum radars. Billions of dollars and decades of research invested in developing radar absorbing materials and optimized shapes for stealth aircrafts like F-117, B-2 and F-22 would become meaningless.
This has led to race between countries to lead this strategic quantum technology. America’s Defence Advanced Research Projects Agency and military suppliers such as Lockheed Martin are also developing quantum radar systems for combat purposes.
In mid-September 2016, however, researchers from China’s Electronic Technology Group Corporation revealed the world’s first long-range quantum radar. China Electronics Technology Group Corporation (CETC) announced, “Chinese scientists have already developed a small, powerful and secure radar system that relies on quantum physics to detect stealth targets located up to 100 kilometers (62 miles) away”. The radar, developed and made by the Nanjing Research Institute of Electronics Technology in Jiangsu province. The institute has been working with the University of Science and Technology of China and Nanjing University along with other research partners in carrying out field tests of the radar’s prototype, and has extensively improved its accuracy and sensitivity, he said. The radar is still undergoing tests and is more like a prototype demonstration of future capabilities, Sun said, adding that future versions will have better anti-stealth properties
“The characteristics of quantum radar include high reliability, accuracy and viability in sophisticated electromagnetic environments. It also has good mobility that will allow it to be mounted on multiple kinds of carriers,” the senior engineer said. “It has resolved traditional radar difficulties in terms of handling stealth targets and surviving enemy countermeasures.”
In addition to these advantages, quantum radars can also be adopted in missile defense and space exploration in the future. They will revolutionize radar arsenals, according to researchers from PLA National University of Defense Technology in Changsha, Hunan province.
At an industry exhibition in Nanjing, capital of eastern China’s Jiangsu province, in JUne 2018 , the company said the latest iteration of the technology could go one step further. Once installed on a near-space vehicle, it could “effectively monitor high-speed flying objects in the upper atmosphere and above”, the company said. Hong Kong-based military commentator Song Zhongping said the development was significant.
“The term ‘high-speed flying objects’ could include ballistic missiles during their boost phase and mid-course, or low-altitude satellites, all of which are important targets to be monitored,” he said. “If a quantum radar could be fully developed, it would be really powerful in the three key areas of range, imaging and counter interference.”
Quantum technology is proving especially useful in scenarios too difficult for conventional systems. Traditional military radar relies on radio waves to detect targets, which consequently make them susceptible to jamming measures. Most existing radar systems cannot detect stealth aircraft because such planes are made of radar-absorbent materials and have “stealthy” aerodynamic designs.
The Quantum radar is a new breed of radar, that is a hybrid system that combines electro-optical and mechanical properties with quantum physics. It uses quantum entanglement between invisible microwave beams and visible light beams to detect hard-to-spot objects.
Quantum radars are based on Quantum illumination, first outlined seven years ago by Seth Lloyd and co-workers of the Massachusetts Institute of Technology. A light beam is split into two beams that are quantum-mechanically entangled, meaning that the quantum states of the photons in each beam are strongly correlated. When two correlated beams interfere in a detector, the signal is amplified compared with uncorrelated beams.
Quantum radars transmit subatomic particles, instead of radio waves, when they search for targets, so they will not be affected by radar-absorbent materials and low-signature designs. Quantum Radar are based on Quantum Entanglement phenomenon in which the physical states of two or more objects such as atoms, photons or ions become so inextricably connected that the state of one particle can instantly influence the state of the other—no matter how far apart they are.
In quantum illumination, one of the two beams (the idler) goes straight to a detector, but the other (the probe) is sent out to sense a target. If the target is present, an echo is reflected from it and travels back to the detector, where it interferes with the idler beam. Even if the entanglement between the two beams is broken up by noise in the environment, some residual correlations remain that affect the interference, so that probe photons can be distinguished from background photons. This makes it possible to identify reflections from the target even when this echo is very weak.
Sending out entangled quanta or photons instead of classical radiation, in theory, offers several advantages. The first is ‘better’ image resolution without an increase in frequency. “The resolution from any visualisation device is directly proportional to the energy of the photons you use to identify the device, and one of the most interesting things about quantum radar is the behaviour of the radar beam as it is propagated through the atmosphere, because the character of the image beamed back is a function of all the photons added together,” explains Ned Allen, the chief scientist at US defence technology company Lockheed Martin.
This means it is possible to get a much higher resolution of targets than classical radar but at the same frequency, even if they have been physically minimised by stealth techniques.
A quantum radar, generating a large number of entangled photon pairs and shooting one twin into the air, would be capable of receiving critical information about a target, including its shape, location, speed, temperature and even the chemical composition of its paint, from returning photons.
Apart from detecting stealthy aircrafts and ships , Quantum radar would have many other military benefits: unlike current radars it would not be detectable hence could not be jammed. The entangled photons would not be detectable therefore give almost no warning or traced back to source hence won’t make the radar vulnerable to anti-radiation missiles like traditional radar.
Moreover, quantum radars are not fooled by traditional radar-jamming tactics. It would also be able to classify and identify the targets and target classes. Since it would be able to determine even the material composition of target , it would be immune to various countermeasures like being able to distinguish decoys from real targets. Therefore Quantum radars shall make the stealth aircrafts highly vulnerable to the modern air defense systems and missiles.
Furthermore, with entangled photons it should be easier to separate background noise from what is actually being reflected back off an object, says Jonathan Baugh, an associate professor at the University of Waterlooís Institute for Quantum Computing (IQC) and the Department of Chemistry, who is leading a quantum radar research project with three other researchers at IQC and the Waterloo Institute for Nanotechnology.
Radar frequencies sometimes suffer because of lots of background noise due to thermal and black body radiation, stray radio signals, or radio noise from things such as solar wind hitting the atmosphere, which can obscure the signal.
Professor at the University of Waterloo in Canada, Baugh is working on a device that’s part of a bigger project to develop quantum radar. Its intended users: stations in the Arctic run by the North American Aerospace Defense Command, or NORAD, a joint US-Canadian organization. The Arctic presents unique challenges for a variety of remote sensing methods including radar. Space weather such as geomagnetic storms, solar radiation storms and solar flares interfere with radar operation and prevent the effective identification of objects.
Baugh said in polar regions, “space weather” can disrupt traditional radar. “This happens to be a situation where using quantum mechanics can help us improve upon current technology,” said Baugh. “We can theoretically reduce the background noise.” A new sensing technique – quantum illumination – will allow radar operators to cut through heavy background noise and isolate objects, including stealth aircraft, with unparalleled accuracy.
Surveillance solutions support the Government of Canada’s ability to exercise sovereignty in the North, and provide a greater awareness of safety and security issues, as well as transportation and commercial activity in Canada’s Arctic. In addition, solutions achieved under the ADSA Program may contribute to joint efforts between Canada and the United States to renew the North Warning System and modernize elements of the North American Aerospace Defense Command (NORAD). Harjit Sajjan, Canadian Defence Minister, said: ‘Radar is our eye in the sky, especially in the Arctic, which presents unique challenges for a variety of remote sensing methods.
Future implementations of quantum illumination at the microwave regime could also be achieved by using other quantum sources, for instance based on Josephson parametric amplifiers, which are able to generate entangled microwave modes of high quality. These amplifiers might become a very good choice once that suitable high-performance microwave photo-detectors are made available, writes Brian Wang.
China claims to have developed quantum radar with 100 km range to bypass stealth measures
A Chinese firm has developed and tested a radar system that uses quantum entanglement to beat the stealth technology of modern military craft, a media report said. The first Chinese quantum radar was developed by the Intelligent Perception Technology Laboratory of the 14th Institute in CETC — Electronics Technology Group Corporation, a defence and electronics firm — Xinhua news agency reported.
Chinese researchers have conducted an experiment that could lead to a way to extend the range at which quantum radar systems can detect stealth aircraft. In a paper in the journal Physical Review Letters, the team from the University of Science and Technology of China (USTC) in Hefei, Anhui province, detailed an experiment that showed for the first time that weak-value-based metrology, an emerging quantum measurement technique, could detect previously undetectable signals.
The radar can see past stealth technologies, and even identify individual features within stealth vehicles, a benefit over conventional Radar systems. The Radar works on the basis of quantum entanglement in photons, where a pair of separated photons share the same state. The system was able to detect a target at a range of 100 kilometres in a real-world environment according to a report by Guangming Online. The new system, according to CETC, has additional advantages, including small size and resilience to countermeasures.
The newly developed radar can be used from a ground station, mounted on an aircraft, or even integrated with a satellite. The device employs single photon detection technology. The technology may also find use in biomedicine, since quantum radar requires lower energy and can be used to non-invasively probe for objects with low reflectivity, such as cancer cells.
CETC said the quantum radar’s advantage was not limited to the detection of stealth planes. The field test had opened a “completely new area of research”, it said, with potential for the development of highly mobile and sensitive radar systems able to survive the most challenging combat engagements.
Challenges in development of Quantum radar
Despite China’s claims to have developed a quantum radar system – which Baugh, Lloyd and Allen dismiss as “not credible” – there are still many technological challenges to realising such a system. The main one is that quantum information is very fragile. “It can be immediately or completely destroyed by the slightest bit of noise or atmosphere disturbance, which is known as decoherence and which destroys its utility,” says Allen.
However, quantum radars have their limitations; like traditional radars, they degrade in resolution over longer distances. This is because the entangled particles do eventually lose the coherence of their quantum state over long distances, a phenomenon which can worsen in adverse weather.
Lockheed, he says, is working to overcome this problem by encasing the quantum photons in a cocoon, which he fondly refers to as “Cinderella’s carriage”. Allen say he believes the Chinese have conducted a successful experiment using a quantum radar system, but that they overcame the decoherence problem by effectively cheating. Chinese researchers, he says, mounted the quantum radar generator on a satellite in space, which essentially means it is not propagating the quantum beam through the atmosphere, but a vacuum. Plus, the receiver was on a high-altitude mountain in Tibet.
“Though they lost 900 million out of 910 milllion photons, ten [million] got through out of chance because they cranked up the power and reduced the atmosphere,” he explains.
In addition, using current technology results in a loss or degradation of the idler photons over time. Ideally, the radar will use quantum memory technology, which is not yet mature. “This loss problem can limit the range of the radar to something like 15 or 20 kilometers potentially, but when one is able to fix this problem using quantum memory, we can expand the range to much more,” Pirandola predicts.
Other challenges to developing quantum radars include creating highly reliable streams of entangled photons and building extremely sensitive detectors. “Because we are working at the single photon level, we are dealing with power levels that are many order of magnitudes weaker than conventional radar systems, which creates a technical challenge,” explains Baugh. Baugh and a team of researchers at the University of Waterloo are developing a reliable source of quantum light to create pairs of photons at a very high rate to build up enough signal to detect things in real time, he explains.
The best entangled photon sources currently generate around 10 million pairs per second using parametric down-conversion. This is an optically pumped technique using a laser and shining it into a non-linear crystal to randomly produce entangled photons. The researchers are building an electrical device that they hope will demonstrate a billion per second or one pair every nanosecond via an electrically driven source that would not be random but controlled.
The new entangled photon source would be directly plugged into a quantum lidar system; it will emit photons in the visible or near infrared regime – or, with wavelength conversion to microwave frequencies, it can be used for quantum radar. With another year and a half to go, Baugh says experiments so far are meeting expectations.
Another drawback of quantum systems is that they require extreme cold, or cryogenic temperatures, to operate. Cryogenic temperatures are somewhere in the neighborhood of minus 238 Fahrenheit. “It’s not a big problem in the lab, of course. But this means the radar should have some sort of refrigerator available. I don’t know how that will affect the size and the shape [of a fielded system],” Pirandola offers
There are other groups, one led by Chris Wilson also at the University of Waterloo, creating entangled photon pairs directly in the microwave region. Another challenge is that the technology will need to work at 4 degrees Kelvin, which is typical for most solid-state quantum technologies to access the quantum states exploited.
One reason the technology will not hit the field soon is that single-photon detectors for optical frequencies are well-developed, but that is not yet the case for microwave detectors. “The problem is that we want to work with microwaves, but we don’t have detectors that are very efficient. Our technique needs detectors that are very good at working at the quantum level—let’s say, a single-photon level,” Pirandola says. “We want to use this device in microwaves for scanning the object, but then we want to use the optical regime for doing the measurements. It’s really the interface between the two regimes that is very important.”
Integrating other technologies, such as tracking devices, also will present a challenge. “In the case of the stealth aircraft, you want to see the reflection far from a potential object in the sky, but also, you would like to include tracking systems, like a Doppler analysis, because the object could be moving, so you may have a Doppler effect,” he says.
And, in practice, it will need to operate in conjunction with what Baugh describes as “really complicated real-time analysis” to make it a feasible system to use, but he adds, “I am optimistic it will be useful”. That quantum radar, once developed, would ‘unstealth stealth planes’ is only a theory, says Lloyd, and it’s more likely that an element of stealithiness would remain. Allen agrees that to say quantum radar will defeat stealth is a “gross over-simplification of the issue”.
“The main benefit of quantum radar, if you had one that worked, would be higher resolution of the image, a much more precise image, which would allow you to detect not only the existence of an intrusive enemy airplane or missile but would allow you to determine its shape, speed and size – how many fins it has and so forth. Whereas with a regular radar you just see a blob and you don’t know what it is,” he says.
Canada awards quantum technology study contract
The Canadian Department of National Defence (DND) has awarded $2.7 million contract to the Institute for Quantum Computing at the University of Waterloo to study new quantum technology in order to improve remote sensing methods in the Arctic region, the Canadian DND announced. The funding will go toward a three-year project that will see the development of quantum radar that will help protect the north, which will be especially crucial with climate change, said MP and Minister of Small Business and Tourism, Bardish Chagger.
“A more accessible north could mean more shipping lanes and more economic development,” said Bardish during her remarks. “However, increased traffic in our north also requires better and more reliable surveillance.” The radar system will use quantum technology to properly scan the north and watch out for potential infiltrators, while increasing safety for those using the waters safely. The team hopes the technology can be used in search and rescue situations as well.
Baugh’s machine generates pairs of photons that are “entangled”—a phenomenon that means the particles of light share a single quantum state. A change in one photon immediately influences the state of the other, even if they are separated by vast distances. Quantum radar operates by taking one photon from every pair generated and firing it out in a microwave beam. The other photon from each pair is held back inside the radar system.
Only a few of the photons sent out will be reflected back if they hit a stealth aircraft. A conventional radar wouldn’t be able to distinguish these returning photons from the mass of other incoming ones created by natural phenomena—or by radar-jamming devices. But a quantum radar can check for evidence that incoming photons are entangled with the ones held back. Any that are must have originated at the radar station. This enables it to detect even the faintest of return signals in a mass of background noise. The method works at extremely low power levels — so low that it can be powered by a battery — and it is resistant to electronic jamming.
Baugh cautions that there are still big engineering challenges. These include developing highly reliable streams of entangled photons and building extremely sensitive detectors. Practical quantum illumination requires on-demand and rapid emission of photons – single particles of light – in entangled (highly correlated) pairs. The light-emitting diode Reimer developed will generate 1,000 times more photons per second than any other technology in the world. It is called a quantum-light source because it sends out light particles that are paired, or in the jargon of quantum scientists, “entangled.”
Producing a lot of these light particles with Reimer’s device is the key to the commercialization of quantum technology. That’s because light particles are extremely fragile — they disperse in the atmosphere, bounce off objects and get dropped during transmission in fibre-optic cables. Producing a billion-per-second with Reimer’s quantum light source ensures there are enough light particles to accomplish the task, whether it is in a radar unit, or a security system for encrypting communications.
Quantum Estimation Methods for Quantum Illumination
Quantum illumination consists in shining quantum light on a target region immersed in a bright thermal bath, with the aim of detecting the presence of a possible low-reflective object. If the signal is entangled with the receiver, then a suitable choice of the measurement offers a gain with respect to the optimal classical protocol employing coherent states.
“Here, we tackle this detection problem by using quantum estimation techniques to measure the reflectivity parameter of the object, showing an enhancement in the signal-to-noise ratio up to 3 dB with respect to the classical case when implementing only local measurements,” write M. Sanz and others. Our approach employs the quantum Fisher information to provide an upper bound for the error probability, supplies the concrete estimator saturating the bound, and extends the quantum illumination protocol to non-Gaussian states. As an example, we show how Schrodinger’s cat states may be used for quantum illumination.
Chinese scientists claims of developing technique to extend the range of quantum radar
The technology used very “gentle” methods to measure the quantum states of subatomic particles repeatedly and could be particularly useful in the detection of extremely weak signals, such as the radar signature of a stealth jet reports Stephen Chen. A quantum physicist at Nanjing University in Jiangsu province, who was not involved in the research, cautioned that it was “laboratory work, not mature enough for immediate field deployment”, but added that it could “boost the range of quantum radar, among other things”.
However, a major challenge faced by quantum radar has been the small number of photons that return, with their number diminishing as the distance to a target increases. The theoretical bottom line was called the shot noise limit, beyond which a target could not be detected even in the best observation conditions.
Beyond the shot noise limit, the information carried by photons would be overwhelmed by the subatomic noises occurring within the photons themselves, and the detector would be unable to take a reliable measurement because the photons would hit the detector like random shots, hence the name.
The USTC team, led by professors Guo Guangcan and Li Chuanfeng, said they broke the shot noise limit by using a refined version of weak quantum measurement technology, which allowed them to accurately detect the presence of a even a very small number of photons. The technology stems from a paradox in quantum physics. In the subatomic world, measurement means destruction. When you measure a subatomic particle you inevitably destroy its original quantum states.
But in the late 1980s, scientists came up with a solution. A weak measurement did not cause a collapse of quantum states. Even though each weak measurement could only obtain a small amount of information, by repeating the measurement on the same particles many times a statistically robust value, or a correct guess, about the properties trying to be measured could be obtained. However, the original weak measurement scheme was inefficient. It could only measure a small proportion of the photons within detection range, with the rest discarded as waste.
In recent years scientists came up with a new method called power recycle measurement which could cycle the photons in a special device to reduce the number being wasted. The USTC team conducted an experiment measuring laser beam deflection to demonstrate how the method could break the shot noise limit and push the sensitivity of a signal detector more than 200 per cent beyond it. They recorded detection at a signal strength less than half the shot noise limit while boosting the accuracy by 150 per cent, they said.
The Nanjing University professor, who requested anonymity, said the technology could “definitely” be used in quantum radar. But a Tsinghua University quantum physicist expressed doubts about whether the technology would find a practical use any time soon, if at all.
“So far I have not heard of any real application of the weak metrology,” he said, also requesting anonymity. “Weak measurement is still a measurement, it will inevitably change the state of the object it measures, and that will set a limit to how far it can go. “There is still ongoing debate whether the weak measurement is showing us real physical observation or just mathematical illusion.”
China’s CETC, has already claimed in 2016 that its radar could detect objects up to 100 kilometers (62 miles) away, has solved these challenges; it’s keeping the technical details of its prototype a secret. A study from just a year earlier set the maximum effective range of quantum radar under 7 miles.
Quantum Radar using microwaves
The same paper by multinational group of researchers proposed in 2015 proposed to a lower frequency frequency, through which background radiation increases dramatically. Using a special converter, they said they could entangle photons with microwaves. The photons—the so-called idler particles—are sent directly to a detector, while microwaves are emitted. If any of the microwaves find their way back to the receiver, a converter changes them into photons before shunting them into the detector. Once at the detector, these microwave–photons could be compared to their formerly entangled companions.
In August, the same group published new research, this time based on experimental results. “In our 2015 theory paper, we suggested using a microwave-to-optical photon conversion, then performing the analysis,” says Seyed Shabir Barzanjeh, a postdoctoral researcher at the Institute of Science and Technology Austria, and the study’s lead author. “But, in our recent experimental paper, we don’t use any photon conversion and directly implemented the microwave quantum illumination/radar.”
In August 2019, Austrian researchers at the Institute of Science and Technology in Klosterneuburg, demonstrated new high-def stealth radar system. Researchers at Austria’s Institute of Science and Technology in Klosterneuburg, Austria, used entangled microwaves to create one of the world’s first quantum radar systems. The newly created radar system offers a low power and precise radar detection system over more conventional radars that we use every day.
According to MIT Technology Review, to create pairs of entangled microwave photons, the Austrian team used a superconducting device called a Josephson parametric converter. They call the photon they beam toward the object of interest the “signal photon,” and the one stored in the device, the “idler photon.”
At the moment the radar only performs well at short distances but could open the door to the creation of stealthy like radar that is almost impossible for adversaries to detect over background noise. Even more so, the technology could offer low-power radar for security applications in populated environments.
Barzanjeh also thinks defense applications of quantum radar are overhyped. “Using our system as it is, I cannot imagine how this can be used for long-range applications and military industries,” he says. Its limited range isn’t the only problem, either. “For now, we only can detect the presence or absence of an object,” he says. “We cannot talk about the shape or distance of the object.”
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