broadsword
Brigadier
That is the streak that runs through him. Whenever China just narrows the gap, his butt hurts so much he needs to be put on death watch. Taxiya got the word right.
News on China's scientific and technological development.
- Thread starter Quickie
- Start date
That is the streak that runs through him. Whenever China just narrows the gap, his butt hurts so much he needs to be put on death watch. Taxiya got the word right.
manqiangrexue
Brigadier
Except here, China's actually widening the gap as it already led with Tianhe-2A but does that a couple fold more with Taihulight as well as with the upcoming exascale designs.
AssassinsMace
Lieutenant General
You know how it was claimed Chinese culture comes from Egypt by the simple logic that both were mummifying people around the same time? Use that simplistic logic and draw your conclusions here.
Recently the new Chinese VLRAAM got a lot of attention in the Western internet military news circles. I read a comment claiming that China stole it from the West. One can't steal something from you that you don't have in the first place or in this case works better. Maybe China can claim Egyptian culture came from Chinese culture just like they tried to claim those pre-Western civilization Caucasian mummies found in far Western China was evidence Chinese culture came from the West.
Recently the new Chinese VLRAAM got a lot of attention in the Western internet military news circles. I read a comment claiming that China stole it from the West. One can't steal something from you that you don't have in the first place or in this case works better. Maybe China can claim Egyptian culture came from Chinese culture just like they tried to claim those pre-Western civilization Caucasian mummies found in far Western China was evidence Chinese culture came from the West.
I agree that we are of poor etiquette because we are a bit sadists if not as much as him being masochist. That is probably why he attracted so many funs.Wow guys, I think it's kind of poor etiquette to continue piling on him like this lol
broadsword
Brigadier
Just be a little careful. He has the home turf advantage.
back on topic, now that we're done with the last round of shenanigans...
Will China convert existing coal plants to nuclear using HTR-PM reactors?
November 21, 2016 By
It would be a huge benefit to the earth’s atmosphere if China, India, Brazil and the US could reduce direct coal burning while still making use of much of the capital that they have invested in building coal fired power plants. It would make an even larger difference in reducing air pollution in the areas downwind of the coal stations.
Converting coal-burning supercritical steam plants to nuclear power plants by replacing the furnaces and boilers with high temperature gas cooled reactors might become a routine power plant improvement in the relatively near future. The High Temperature Reactor – Power Module (HTR-PM) project is aimed at demonstrating the feasibility of this evolutionary concept.
At the recent , held in Las Vegas, NV, , Director of China’s Institute of Nuclear and New Energy Technologies (INET), briefed his colleagues in the international community of high temperature gas reactor enthusiasts on the current status of the HTR-PM. That project is one of the more intriguing clean air projects underway in the world today.
The end of Zhang Zuoyi’s brief resulted in a sustained round of clapping; there were even a few hoots from the attending scientists and engineers that would have been more expected at a football match. (Most attendees at this talk were not from the US, the word “match” is intentional.)
Some of the audience members were able to trace their involvement and excitement about HTRs back more than 40 years to hands-on experience in the construction and operation of the Peach Bottom 1 nuclear plant, a project that was during the period from 1958 – 1978. The attendees were nearly unanimous in their appreciation of the fact that someone, somewhere was building commercial plants using the technology they had been working on for so long.
Target Market
China’s HTR-PM project is squarely aimed at being a cost-effective solution that will virtually eliminate air pollution and CO2 production from selected units of China’s large installed base of modern 600 MWe supercritical coal plants.
This is not a “pie-in-the-sky” long range plan to eventually replace those built facilities and leave idle capital rotting away. Instead, it is a deployment program with the first of a kind commercial demonstration approaching construction completion and commercial operation by mid to late 2018. Major parts of the machinery will be able to be merged into the existing infrastructure.
Schedule
The commercial operation date is six to nine months later than scheduled when construction began, but Prof. Zhang Zuoyi proudly explained that the HTR-PM first-of-a-kind delays were much shorter than the 3-4 year delays that have plagued the EPR and AP1000 construction projects in their country.
The current critical path item is the completion of the steam generators — one for each of the two reactors. The shells and internals have been completed, but the final stages of attaching the piping to the thick-walled, large diameter pressure vessels will delay site delivery until sometime close to the middle of 2017.
Development Challenges
Zhang Zuoyi gave an excellent overview of the design and testing challenges that the project has faced and overcome. Nearly every item on the list of critical steps for design and testing had been completed.
For example, the development effort included building four different prototypes for the helium circulators. The primary design included magnetic bearings, but the developers knew that they were well past the size limits of proven uses of magnetic bearings so they had a couple of fall back designs. They did not want the project to fail because of failure to deliver on a single component.
In another example, the reactor pressure vessels weigh in at 600 tons, making the act of a very heavy lift that exceeded previously existing capabilities.
The learning that has been gained during the challenging task of construction and component manufacturing and the learning that will be gained during the operation of a plant that uses two nuclear heated boilers to power a single steam turbine will form a solid foundation for the next step.
As operational experience is gained with the first unit, the developers will be building more boilers and installing them in configurations of six to twelve boilers providing steam to a single steam turbine.
One of the items that was learned during construction of the lead unit was that the plant footprint could be reduced by about 50% by arranging the boilers in circles with three boilers in each circle instead of lining them all up side by side.
Increasing Value Of Existing Infrastructure
In some cases, these nuclear boiler installations will be part of entirely new power stations. The more intriguing aspect of the concept, however, is the fact that the high temperature atomic boilers produce steam conditions that are identical to the design conditions for a large series of modern, 600 MWe steam plants that currently use coal as the heat source.
During the question and answer period, Prof. Zhang Zuoyi responded to my questions by confirming that some of the pebble-bed atomic boilers will be installed as replacement heat sources for existing steam plants. Those installations will be able to take advantage of the switchyards, the installed transmission networks, the cooling water systems, the sites and in some cases the entire steam plant including the steam turbine.
The priority for replacing coal boilers with nuclear boilers will be at power plants in areas with major pollution problems. Those plants are often located very close to population centers; that reality is one of the reasons that China has invested in developing reactors that can be tested and proven to be safe.
The HTR-PM modules can withstand complete loss of pressurization and helium flow without a forced shutdown and still not release enough radioactive materials to exceed the very conservative dose limits in place today.
Cost And Value
The overall cost of this first of a kind nuclear plant will be in the neighborhood of $5000.00/kw of capacity. That number is based on signed and mostly executed contracts, not early estimates. It is about twice the initially expected cost. According to Zhang Zuoyi, 35% of the increased cost could be attributed to higher material and component costs that initially budgeted, 31% of the increase was due to increases in labor costs — which Zhang Zuoyi noted were rising rapidly in China — and the remainder due to the increased costs associated with the project delays.
Zhang Zuoyi described the techniques that will be applied to lower the costs; he expects them to soon approach the $2,000 to $2,500 / kw capacity range.
The value proposition of these clean replacement boilers, however, will be more than just economical electricity. The real payoff will be the ability to enjoy the fruits of economic development without as much difficulty in merely taking a breath.
Will China convert existing coal plants to nuclear using HTR-PM reactors?
November 21, 2016 By
It would be a huge benefit to the earth’s atmosphere if China, India, Brazil and the US could reduce direct coal burning while still making use of much of the capital that they have invested in building coal fired power plants. It would make an even larger difference in reducing air pollution in the areas downwind of the coal stations.
Converting coal-burning supercritical steam plants to nuclear power plants by replacing the furnaces and boilers with high temperature gas cooled reactors might become a routine power plant improvement in the relatively near future. The High Temperature Reactor – Power Module (HTR-PM) project is aimed at demonstrating the feasibility of this evolutionary concept.
At the recent , held in Las Vegas, NV, , Director of China’s Institute of Nuclear and New Energy Technologies (INET), briefed his colleagues in the international community of high temperature gas reactor enthusiasts on the current status of the HTR-PM. That project is one of the more intriguing clean air projects underway in the world today.
The end of Zhang Zuoyi’s brief resulted in a sustained round of clapping; there were even a few hoots from the attending scientists and engineers that would have been more expected at a football match. (Most attendees at this talk were not from the US, the word “match” is intentional.)
Some of the audience members were able to trace their involvement and excitement about HTRs back more than 40 years to hands-on experience in the construction and operation of the Peach Bottom 1 nuclear plant, a project that was during the period from 1958 – 1978. The attendees were nearly unanimous in their appreciation of the fact that someone, somewhere was building commercial plants using the technology they had been working on for so long.
Target Market
China’s HTR-PM project is squarely aimed at being a cost-effective solution that will virtually eliminate air pollution and CO2 production from selected units of China’s large installed base of modern 600 MWe supercritical coal plants.
This is not a “pie-in-the-sky” long range plan to eventually replace those built facilities and leave idle capital rotting away. Instead, it is a deployment program with the first of a kind commercial demonstration approaching construction completion and commercial operation by mid to late 2018. Major parts of the machinery will be able to be merged into the existing infrastructure.
Schedule
The commercial operation date is six to nine months later than scheduled when construction began, but Prof. Zhang Zuoyi proudly explained that the HTR-PM first-of-a-kind delays were much shorter than the 3-4 year delays that have plagued the EPR and AP1000 construction projects in their country.
The current critical path item is the completion of the steam generators — one for each of the two reactors. The shells and internals have been completed, but the final stages of attaching the piping to the thick-walled, large diameter pressure vessels will delay site delivery until sometime close to the middle of 2017.
Development Challenges
Zhang Zuoyi gave an excellent overview of the design and testing challenges that the project has faced and overcome. Nearly every item on the list of critical steps for design and testing had been completed.
For example, the development effort included building four different prototypes for the helium circulators. The primary design included magnetic bearings, but the developers knew that they were well past the size limits of proven uses of magnetic bearings so they had a couple of fall back designs. They did not want the project to fail because of failure to deliver on a single component.
In another example, the reactor pressure vessels weigh in at 600 tons, making the act of a very heavy lift that exceeded previously existing capabilities.
The learning that has been gained during the challenging task of construction and component manufacturing and the learning that will be gained during the operation of a plant that uses two nuclear heated boilers to power a single steam turbine will form a solid foundation for the next step.
As operational experience is gained with the first unit, the developers will be building more boilers and installing them in configurations of six to twelve boilers providing steam to a single steam turbine.
One of the items that was learned during construction of the lead unit was that the plant footprint could be reduced by about 50% by arranging the boilers in circles with three boilers in each circle instead of lining them all up side by side.
Increasing Value Of Existing Infrastructure
In some cases, these nuclear boiler installations will be part of entirely new power stations. The more intriguing aspect of the concept, however, is the fact that the high temperature atomic boilers produce steam conditions that are identical to the design conditions for a large series of modern, 600 MWe steam plants that currently use coal as the heat source.
During the question and answer period, Prof. Zhang Zuoyi responded to my questions by confirming that some of the pebble-bed atomic boilers will be installed as replacement heat sources for existing steam plants. Those installations will be able to take advantage of the switchyards, the installed transmission networks, the cooling water systems, the sites and in some cases the entire steam plant including the steam turbine.
The priority for replacing coal boilers with nuclear boilers will be at power plants in areas with major pollution problems. Those plants are often located very close to population centers; that reality is one of the reasons that China has invested in developing reactors that can be tested and proven to be safe.
The HTR-PM modules can withstand complete loss of pressurization and helium flow without a forced shutdown and still not release enough radioactive materials to exceed the very conservative dose limits in place today.
Cost And Value
The overall cost of this first of a kind nuclear plant will be in the neighborhood of $5000.00/kw of capacity. That number is based on signed and mostly executed contracts, not early estimates. It is about twice the initially expected cost. According to Zhang Zuoyi, 35% of the increased cost could be attributed to higher material and component costs that initially budgeted, 31% of the increase was due to increases in labor costs — which Zhang Zuoyi noted were rising rapidly in China — and the remainder due to the increased costs associated with the project delays.
Zhang Zuoyi described the techniques that will be applied to lower the costs; he expects them to soon approach the $2,000 to $2,500 / kw capacity range.
The value proposition of these clean replacement boilers, however, will be more than just economical electricity. The real payoff will be the ability to enjoy the fruits of economic development without as much difficulty in merely taking a breath.
broadsword
Brigadier
Good News for battery lovers
Huawei's technology recharges 48% of a 3000mAh battery in just 5 minutes.
For comparison, LG's G5 recharges 33% in 15 minutes.
Huawei achieves major breakthrough in graphene-assisted high temperature Li-ion batteries
() 15:14, December 02, 2016
(Photo/Huawei)
Huawei announced a major breakthrough in its research into Li-ion batteries, unveiling the world's first long-lifespan graphene-assisted Li-ion battery able to withstand high temperatures. The announcement was made by Watt Laboratory, an organization under Huawei's Central Research Institute, at the 57th Battery Symposium held in Japan.
Huawei's research results show that new graphene-based heat-resistant technologies allow Li-ion batteries to remain functional in a 60°C environment, a temperature 10°C higher than the existing upper limit. The lifespan of the graphene-assisted Li-ion batteries will also be twice as long as ordinary Li-ion batteries.
Dr. Yangxing Li, Chief Scientist at Watt Laboratory, pointed out that three technologies contributed to the breakthrough in the graphene-assisted high-temperature Li-ion battery. First, a special additive in the electrolytes can remove trace water and prevent the electrolytes from evaporating in high temperatures. Second, modified large-crystal NMC materials are used for the cathode, improving the thermal stability of the cathode powder. Third, graphene allows for more efficient cooling of the Li-ion battery.
(Photo/Huawei)
Dr. Li said, "We have performed charging and discharging tests in a high-temperature environment. The tests show that when working parameters are the same, the graphene-assisted high-temperature Li-ion battery is 5°C cooler than ordinary Li-ion batteries. Over 70% of the graphene battery's capacity is left after it is recharged 2,000 times at a temperature of 60°C. Less than 13% of its capacity is lost after being kept in a 60°C environment for 200 days."
Huawei's research results will reshape the storage systems of communications base stations. In high-temperature regions, outdoor base stations powered by the graphene-assisted high-temperature Li-ion batteries can have working lifespans longer than four years. These batteries ensure a high mileage for electric vehicles per charge in high temperatures. They can also guarantee the safe operation of drones, which often generate a significant amount of heat.
At the 56th Battery Symposium also held in Japan in 2015, Huawei's Watt Laboratory revealed its quick charging technology, which recharges 48% of a 3000mAh battery in just 5 minutes. This technology turned many heads. According to Dr. Li, Huawei has commercialized the developed quick charging batteries and will announce a super-quick charging mobile phone in late December.
Huawei's technology recharges 48% of a 3000mAh battery in just 5 minutes.
For comparison, LG's G5 recharges 33% in 15 minutes.
Huawei achieves major breakthrough in graphene-assisted high temperature Li-ion batteries
() 15:14, December 02, 2016
(Photo/Huawei)
Huawei announced a major breakthrough in its research into Li-ion batteries, unveiling the world's first long-lifespan graphene-assisted Li-ion battery able to withstand high temperatures. The announcement was made by Watt Laboratory, an organization under Huawei's Central Research Institute, at the 57th Battery Symposium held in Japan.
Huawei's research results show that new graphene-based heat-resistant technologies allow Li-ion batteries to remain functional in a 60°C environment, a temperature 10°C higher than the existing upper limit. The lifespan of the graphene-assisted Li-ion batteries will also be twice as long as ordinary Li-ion batteries.
Dr. Yangxing Li, Chief Scientist at Watt Laboratory, pointed out that three technologies contributed to the breakthrough in the graphene-assisted high-temperature Li-ion battery. First, a special additive in the electrolytes can remove trace water and prevent the electrolytes from evaporating in high temperatures. Second, modified large-crystal NMC materials are used for the cathode, improving the thermal stability of the cathode powder. Third, graphene allows for more efficient cooling of the Li-ion battery.
(Photo/Huawei)
Dr. Li said, "We have performed charging and discharging tests in a high-temperature environment. The tests show that when working parameters are the same, the graphene-assisted high-temperature Li-ion battery is 5°C cooler than ordinary Li-ion batteries. Over 70% of the graphene battery's capacity is left after it is recharged 2,000 times at a temperature of 60°C. Less than 13% of its capacity is lost after being kept in a 60°C environment for 200 days."
Huawei's research results will reshape the storage systems of communications base stations. In high-temperature regions, outdoor base stations powered by the graphene-assisted high-temperature Li-ion batteries can have working lifespans longer than four years. These batteries ensure a high mileage for electric vehicles per charge in high temperatures. They can also guarantee the safe operation of drones, which often generate a significant amount of heat.
At the 56th Battery Symposium also held in Japan in 2015, Huawei's Watt Laboratory revealed its quick charging technology, which recharges 48% of a 3000mAh battery in just 5 minutes. This technology turned many heads. According to Dr. Li, Huawei has commercialized the developed quick charging batteries and will announce a super-quick charging mobile phone in late December.
soon we will see Huawei branded e-cars on the street.Good News for battery lovers
Huawei's technology recharges 48% of a 3000mAh battery in just 5 minutes.
For comparison, LG's G5 recharges 33% in 15 minutes.
Huawei achieves major breakthrough in graphene-assisted high temperature Li-ion batteries
() 15:14, December 02, 2016
(Photo/Huawei)
Huawei announced a major breakthrough in its research into Li-ion batteries, unveiling the world's first long-lifespan graphene-assisted Li-ion battery able to withstand high temperatures. The announcement was made by Watt Laboratory, an organization under Huawei's Central Research Institute, at the 57th Battery Symposium held in Japan.
Huawei's research results show that new graphene-based heat-resistant technologies allow Li-ion batteries to remain functional in a 60°C environment, a temperature 10°C higher than the existing upper limit. The lifespan of the graphene-assisted Li-ion batteries will also be twice as long as ordinary Li-ion batteries.
Dr. Yangxing Li, Chief Scientist at Watt Laboratory, pointed out that three technologies contributed to the breakthrough in the graphene-assisted high-temperature Li-ion battery. First, a special additive in the electrolytes can remove trace water and prevent the electrolytes from evaporating in high temperatures. Second, modified large-crystal NMC materials are used for the cathode, improving the thermal stability of the cathode powder. Third, graphene allows for more efficient cooling of the Li-ion battery.
(Photo/Huawei)
Dr. Li said, "We have performed charging and discharging tests in a high-temperature environment. The tests show that when working parameters are the same, the graphene-assisted high-temperature Li-ion battery is 5°C cooler than ordinary Li-ion batteries. Over 70% of the graphene battery's capacity is left after it is recharged 2,000 times at a temperature of 60°C. Less than 13% of its capacity is lost after being kept in a 60°C environment for 200 days."
Huawei's research results will reshape the storage systems of communications base stations. In high-temperature regions, outdoor base stations powered by the graphene-assisted high-temperature Li-ion batteries can have working lifespans longer than four years. These batteries ensure a high mileage for electric vehicles per charge in high temperatures. They can also guarantee the safe operation of drones, which often generate a significant amount of heat.
At the 56th Battery Symposium also held in Japan in 2015, Huawei's Watt Laboratory revealed its quick charging technology, which recharges 48% of a 3000mAh battery in just 5 minutes. This technology turned many heads. According to Dr. Li, Huawei has commercialized the developed quick charging batteries and will announce a super-quick charging mobile phone in late December.
Hendrik_2000
Lieutenant General
About couple month ago we have news about quantum radar .Now the chinese say they might be able to increase the range of the radar
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 in the journal Physical Review Letters early this month, 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 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.
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”.
Quantum physicists at USTC have built the world’s first quantum satellite, which was launched in August, and its longest ground-based quantum communication network.
USTC researchers also participated in the development of China’s first quantum radar system, according to China Electronics Technology Group Corporation (CETC), a state-owned arms supplier.
Earlier this year, CETC announced the effective range of Chinese quantum radar technology had reached 100km, five times the potential range of an overseas prototype.
China regards the stealth aircraft flown by the United States and its allies as a major threat to its regional interests. Japan received its first F-35 stealth fighter last month and in the years ahead China faces the likelihood of being surrounded by more stealth fighters and bombers.
Quantum radar systems generate pairs of entangled light particles known as photons. One photon in the pair is beamed into the air while the other is kept at the radar station. If a target is located, some photons bounce back and can be identified by matching them with the entangled photons kept at the radar station. By measuring the returning photons, researchers can calculate the physical properties of the target, such as its size, shape, speed and angle of attack.
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.”
This article appeared in the South China Morning Post print edition as:
forcing stealth jets Above the radar
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 in the journal Physical Review Letters early this month, 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 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.
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”.
Quantum physicists at USTC have built the world’s first quantum satellite, which was launched in August, and its longest ground-based quantum communication network.
USTC researchers also participated in the development of China’s first quantum radar system, according to China Electronics Technology Group Corporation (CETC), a state-owned arms supplier.
Earlier this year, CETC announced the effective range of Chinese quantum radar technology had reached 100km, five times the potential range of an overseas prototype.
China regards the stealth aircraft flown by the United States and its allies as a major threat to its regional interests. Japan received its first F-35 stealth fighter last month and in the years ahead China faces the likelihood of being surrounded by more stealth fighters and bombers.
Quantum radar systems generate pairs of entangled light particles known as photons. One photon in the pair is beamed into the air while the other is kept at the radar station. If a target is located, some photons bounce back and can be identified by matching them with the entangled photons kept at the radar station. By measuring the returning photons, researchers can calculate the physical properties of the target, such as its size, shape, speed and angle of attack.
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.”
This article appeared in the South China Morning Post print edition as:
forcing stealth jets Above the radar