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100Km is an unbelievable achievement. You need some insane memory for that.
China Quantum Communiations Technology: Cryptography, Radar, Satellite, Teleportation, Network
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beijingwalker
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China’s 2,000-km Quantum Link Is Almost Complete
The Beijing-Shanghai project will form the backbone of the nation’s quantum communications network
By Rachel Courtland
Posted 26 Oct 2016 | 15:00 GMt
Quantum Space Link: Staff work on China’s quantum research satellite, which launched in August. It is part of a larger effort in the country to push the limits of quantum key distribution.
By the end of this year, a team led by researchers from the University of Science and Technology of China, in Hefei, aims to put the finishing touches on a 2,000-kilometer-long fiber-optic link that will wind its way from Beijing in the north to the coastal city of Shanghai.
What will distinguish this particular stretch of fiber from myriad other long-distance links is its intended application: the exchange of quantum keys for secure communication—a sophisticated gambit to protect data from present and future hackers. If all goes according to plan, this Beijing–Shanghai line will connect quantum networks in four cities. And this large-scale terrestrial effort now has a partner in space: A quantum science satellite was launched in August with a research mission that includes testing the distribution of keys well beyond the country’s borders.
With these developments, China is poised to vastly extend the reach of quantum key distribution (QKD), an approach for creating shared cryptographic keys—sequences of random bits—that can be used to encrypt and decrypt data. Thanks to the fundamental nature of quantum mechanics, QKD has the distinction of being, in principle, unhackable. A malicious party that attempts to eavesdrop on a quantum transmission won’t be able to do so without creating detectable errors.
QKD has already made its way into the real world. In 2007, the scheme was used to secure the transmission of votes in a Swiss election. Several years ago, the U.S.-based firm Battelle began to use the approach to exchange information securely over kilometers of fiber between its corporate headquarters in Columbus, Ohio, and a production facility in Dublin, Ohio.
But despite great progress, there has been a stumbling block to wide distribution. “The problem we’ve got is distance,” says Tim Spiller, director of the United Kingdom’s Quantum Communications Hub, a nationally funded project that is building and connecting quantum networks in Bristol and Cambridge, in England.
The challenge is that QKD encodes information in the states of individual photons. And those photons can’t travel indefinitely in fiber or through the air; the longer the distance, the greater the chance they will be absorbed or scattered.
This characteristic has a direct impact on how quickly a quantum key can be generated, explains physicist Jian-Wei Pan, who leads the Chinese projects. If researchers attempted to send signals directly down 1,000 kilometers of fiber, Pan says, “even using all the best technology, we would only manage to send 1 bit of secure key over 300 years.”
Instead, QKD fiber links must have a way to refresh the signal every 100 km or so to maintain a reasonable bit rate. But this can’t be done with conventional telecommunications equipment. The same rules that protect quantum transmission against eavesdropping also prohibit a quantum key from being copied without corrupting it. The solution has been to concatenate, creating a daisy chain of individual quantum links connected by physically secured spots, or “trusted nodes.” Each intermediate node measures the key and then transmits it with fresh photons to the next node in the chain.
The Beijing–Shanghai line will use 32 trusted nodes to create the 2,000-km line. This approach isn’t ideal for security. Because each trusted node has to convert the quantum key back into classical (nonquantum) information before passing it on, an eavesdropper at the node could potentially hack the data stream there undetected. “That’s the drawback,” Pan says. But the approach is “still much better than traditional communications… [where] there is the possibility of performing eavesdropping” at every point along the route, he says. Here, the problem is limited to 32 spots under lock and key.
“A long-distance chain link like this, [it’s] really the first time it’s been done,” says Grégoire Ribordy of ID Quantique, based in Geneva, which makes hardware for QKD networks. “It’s inspiring other people to try to do similar things around the world.”
If you want to avoid even the small vulnerability of trusted nodes, Spiller says, long-distance QKD must use quantum entanglement, a property that can link the states of photons separated by great physical distance and that can be exchanged between photons. “Quantum repeaters,” used in place of trusted nodes, could take advantage of this phenomenon to relay a quantum key without having to measure it. But this technology is still in an early stage of development, says Spiller; among other things, a quantum repeater will likely require a form of quantum memory to help coordinate communication.
“[If you] don’t have to trust any of the nodes along the network, that will broaden the applicability of QKD,” says Michele Mosca, cofounder of the Institute for Quantum Computing at the University of Waterloo, in Ontario, Canada. One reason to improve QKD’s reach is to protect communications from tomorrow’s quantum computers, which could make short work of the public-key cryptography that underpins Internet security and many other applications.
But Mosca notes that QKD is not the only possible way to address this threat; many cryptographers are exploring new “post-quantum” algorithms to replace our existing public-key systems. QKD offers an “extra degree of assurance,” he says, but improved conventional cryptography will be a cheaper and more practical solution for many applications. Both will likely have a role to play in the coming years.
http://spectrum.ieee.org/telecom/security/chinas-2000km-quantum-link-is-almost-complete
The Beijing-Shanghai project will form the backbone of the nation’s quantum communications network
By Rachel Courtland
Posted 26 Oct 2016 | 15:00 GMt
Quantum Space Link: Staff work on China’s quantum research satellite, which launched in August. It is part of a larger effort in the country to push the limits of quantum key distribution.
By the end of this year, a team led by researchers from the University of Science and Technology of China, in Hefei, aims to put the finishing touches on a 2,000-kilometer-long fiber-optic link that will wind its way from Beijing in the north to the coastal city of Shanghai.
What will distinguish this particular stretch of fiber from myriad other long-distance links is its intended application: the exchange of quantum keys for secure communication—a sophisticated gambit to protect data from present and future hackers. If all goes according to plan, this Beijing–Shanghai line will connect quantum networks in four cities. And this large-scale terrestrial effort now has a partner in space: A quantum science satellite was launched in August with a research mission that includes testing the distribution of keys well beyond the country’s borders.
With these developments, China is poised to vastly extend the reach of quantum key distribution (QKD), an approach for creating shared cryptographic keys—sequences of random bits—that can be used to encrypt and decrypt data. Thanks to the fundamental nature of quantum mechanics, QKD has the distinction of being, in principle, unhackable. A malicious party that attempts to eavesdrop on a quantum transmission won’t be able to do so without creating detectable errors.
QKD has already made its way into the real world. In 2007, the scheme was used to secure the transmission of votes in a Swiss election. Several years ago, the U.S.-based firm Battelle began to use the approach to exchange information securely over kilometers of fiber between its corporate headquarters in Columbus, Ohio, and a production facility in Dublin, Ohio.
But despite great progress, there has been a stumbling block to wide distribution. “The problem we’ve got is distance,” says Tim Spiller, director of the United Kingdom’s Quantum Communications Hub, a nationally funded project that is building and connecting quantum networks in Bristol and Cambridge, in England.
The challenge is that QKD encodes information in the states of individual photons. And those photons can’t travel indefinitely in fiber or through the air; the longer the distance, the greater the chance they will be absorbed or scattered.
This characteristic has a direct impact on how quickly a quantum key can be generated, explains physicist Jian-Wei Pan, who leads the Chinese projects. If researchers attempted to send signals directly down 1,000 kilometers of fiber, Pan says, “even using all the best technology, we would only manage to send 1 bit of secure key over 300 years.”
Instead, QKD fiber links must have a way to refresh the signal every 100 km or so to maintain a reasonable bit rate. But this can’t be done with conventional telecommunications equipment. The same rules that protect quantum transmission against eavesdropping also prohibit a quantum key from being copied without corrupting it. The solution has been to concatenate, creating a daisy chain of individual quantum links connected by physically secured spots, or “trusted nodes.” Each intermediate node measures the key and then transmits it with fresh photons to the next node in the chain.
The Beijing–Shanghai line will use 32 trusted nodes to create the 2,000-km line. This approach isn’t ideal for security. Because each trusted node has to convert the quantum key back into classical (nonquantum) information before passing it on, an eavesdropper at the node could potentially hack the data stream there undetected. “That’s the drawback,” Pan says. But the approach is “still much better than traditional communications… [where] there is the possibility of performing eavesdropping” at every point along the route, he says. Here, the problem is limited to 32 spots under lock and key.
“A long-distance chain link like this, [it’s] really the first time it’s been done,” says Grégoire Ribordy of ID Quantique, based in Geneva, which makes hardware for QKD networks. “It’s inspiring other people to try to do similar things around the world.”
If you want to avoid even the small vulnerability of trusted nodes, Spiller says, long-distance QKD must use quantum entanglement, a property that can link the states of photons separated by great physical distance and that can be exchanged between photons. “Quantum repeaters,” used in place of trusted nodes, could take advantage of this phenomenon to relay a quantum key without having to measure it. But this technology is still in an early stage of development, says Spiller; among other things, a quantum repeater will likely require a form of quantum memory to help coordinate communication.
“[If you] don’t have to trust any of the nodes along the network, that will broaden the applicability of QKD,” says Michele Mosca, cofounder of the Institute for Quantum Computing at the University of Waterloo, in Ontario, Canada. One reason to improve QKD’s reach is to protect communications from tomorrow’s quantum computers, which could make short work of the public-key cryptography that underpins Internet security and many other applications.
But Mosca notes that QKD is not the only possible way to address this threat; many cryptographers are exploring new “post-quantum” algorithms to replace our existing public-key systems. QKD offers an “extra degree of assurance,” he says, but improved conventional cryptography will be a cheaper and more practical solution for many applications. Both will likely have a role to play in the coming years.
http://spectrum.ieee.org/telecom/security/chinas-2000km-quantum-link-is-almost-complete
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PatriotNaz
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Ive watched how these satellites work when sending data and it still baffling and i love science
cirr
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Synopsis: Quantum Cryptography Goes a Long Way
November 2, 2016
A protocol for secure quantum communications has been demonstrated over a record-breaking distance of 404 km.
Y. Hua-Lei et al., Phys. Rev. Lett. (2016)
Encryption is critical in many aspects of modern life, such as the millions of credit card transactions that occur every day. However, perfectly secure communication can only be achieved using the strong correlations, or entanglement, between quantum objects. Now, Jian-Wei Pan at the University of Science and Technology of China and his colleagues have experimentally shown that a secure quantum protocol known as measurement-device-independent quantum key distribution (MDIQKD) can be implemented over a distance of 404 km. The result breaks the previous MDIQKD record by over a factor of 2 and paves the way for secure quantum communications between distant cities.
MDIQKD—a protocol proposed in 2012—functions even when it uses photon detectors that are not ideal and have, for example, low detection efficiencies. It can also overcome security loopholes of quantum communication schemes by sending out decoy pulses of light to detect eavesdropping attacks. Pan and his team sent pulses of infrared photons through optical fibers with lengths between 102 and 404 km and optimized the MDIQKD scheme by tuning several parameters, such as the average number of photons per pulse. The protocol was found to be secure up to the longest distance. For each length, the researchers also determined the maximum speed by which cryptographic keys could be securely distributed. Compared with earlier experiments, they demonstrated a 500-fold increase in speed, reaching a key-distribution rate that would be sufficient to ensure encrypted voice transmission by telephone.
This research is published in Physical Review Letters.
–Katherine Kornei
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.117.190501
November 2, 2016
A protocol for secure quantum communications has been demonstrated over a record-breaking distance of 404 km.
Y. Hua-Lei et al., Phys. Rev. Lett. (2016)
Encryption is critical in many aspects of modern life, such as the millions of credit card transactions that occur every day. However, perfectly secure communication can only be achieved using the strong correlations, or entanglement, between quantum objects. Now, Jian-Wei Pan at the University of Science and Technology of China and his colleagues have experimentally shown that a secure quantum protocol known as measurement-device-independent quantum key distribution (MDIQKD) can be implemented over a distance of 404 km. The result breaks the previous MDIQKD record by over a factor of 2 and paves the way for secure quantum communications between distant cities.
MDIQKD—a protocol proposed in 2012—functions even when it uses photon detectors that are not ideal and have, for example, low detection efficiencies. It can also overcome security loopholes of quantum communication schemes by sending out decoy pulses of light to detect eavesdropping attacks. Pan and his team sent pulses of infrared photons through optical fibers with lengths between 102 and 404 km and optimized the MDIQKD scheme by tuning several parameters, such as the average number of photons per pulse. The protocol was found to be secure up to the longest distance. For each length, the researchers also determined the maximum speed by which cryptographic keys could be securely distributed. Compared with earlier experiments, they demonstrated a 500-fold increase in speed, reaching a key-distribution rate that would be sufficient to ensure encrypted voice transmission by telephone.
This research is published in Physical Review Letters.
–Katherine Kornei
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.117.190501
Shotgunner51
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Chinese Physicists Achieve Record-Breaking Quantum Cryptography Breakthrough
by Giulio Prisco November 4, 2016
Researchers at the University of Science and Technology of China and other Chinese labs, with the collaboration of a lab in the US, have implemented a secure quantum protocol known as Measurement-Device-Independent Quantum Key Distribution (MDIQKD), suitable for practical networks and devices, over a distance of 404 km. The breakthrough, which doubles the previous MDIQKD record, opens the door to secure wide area quantum communication networks.
The research was published earlier this week (November 2) in Physical Review Letters with the title “Measurement-Device-Independent Quantum Key Distribution Over a 404 km Optical Fiber.” A companion “Synopsis: Quantum Cryptography Goes a Long Way” was published in APS Physics.
The researchers note that, while the potential of Quantum Key Distribution (QKD) to provide unconditional secure communication between two distant parties is undisputed, its feasibility has been questioned due to certain limitations in the practical application of real-life QKD systems. The new method is seen as an important step toward practical, operational QKD networks.
Quantum Key Distribution permits securely sharing keys for one-time pad (OTP) cryptography. OTP encryption is mathematically guaranteed to be unbreakable, but only if the keys are not compromised. Therefore, secure key transmission and storage is the main challenge for ultra-secure OTP cryptography. But quantum entanglement – long-range instant correlations between photons – can be used to establish a shared key in such a way as to permit detecting any attempt to eavesdrop on the key. Therefore, quantum encryption offers complete, invulnerable security based on the laws of fundamental physics.
Quantum computing, a complementary quantum technology, first proposed by Nobel laureate Richard P. Feynman in 1982 (see also Feynman’s Lectures on Computation), could in the future permit cracking all traditional encryption schemes with sophisticated algorithms and superior computing power. But quantum encryption is invulnerable to quantum computing attacks.
Toward fast, Secure, Unbreakable Wide Area Quantum Encryption Network
MDIQKD – a quantum cryptography protocol first proposed in 2012 – tolerates relatively inefficient photon detectors and permits improving the security of quantum communication by using “decoy” photons to detect eavesdropping attacks. The researchers sent infrared photons through optical fibers with lengths between 102 and 404 km, and demonstrated security up to the longest distance.
“Measurement-device-independent quantum key distribution (MDIQKD) with the decoy-state method negates security threats of both the imperfect single-photon source and detection losses,” reads the paper’s abstract. “Lengthening the distance and improving the key rate of quantum key distribution (QKD) are vital issues in practical applications of QKD. Herein, we report the results of MDIQKD over 404 km of ultralow-loss optical fiber and 311 km of a standard optical fiber while employing an optimized four-intensity decoy-state method.”
MDIQKD had proven very slow so far, compared to the requirements for practical QKD. “The best demonstration so far sent information over a distance of 200 kilometers at a data rate of just 0.018 bits per second,” noted a MIT Technology Review commentary to a draft version of the paper. “At this rate, perfectly secure quantum cryptography would never be practical.” But now the Chinese scientists have achieved a very significant increase in speed compared to previous results.
The scientists added that system performance could be further improved by increasing the system clock rate and the efficiency of the photon detectors.
Physicists at Corning Inc., a research company headquartered in Corning, New York, and specialized in materials science and optical physics, have participated in the research. Among them, fiber optics and quantum communication specialist Daniel Nolan.
But it appears that China is pursuing a government-supported, well-funded quantum technology development effort for both civilian and military applications, ranging from unbreakable encrypted communication networks to combat support operations, more aggressively than the US. Early results of China’s quantum technology program are the world’s first quantum satellite and a “quantum radar” able to detect stealth planes 100km away, both recently covered by Hacked.
https://hacked.com/chinese-physicists-achieve-record-breaking-quantum-cryptography-breakthrough/
by Giulio Prisco November 4, 2016
Researchers at the University of Science and Technology of China and other Chinese labs, with the collaboration of a lab in the US, have implemented a secure quantum protocol known as Measurement-Device-Independent Quantum Key Distribution (MDIQKD), suitable for practical networks and devices, over a distance of 404 km. The breakthrough, which doubles the previous MDIQKD record, opens the door to secure wide area quantum communication networks.
The research was published earlier this week (November 2) in Physical Review Letters with the title “Measurement-Device-Independent Quantum Key Distribution Over a 404 km Optical Fiber.” A companion “Synopsis: Quantum Cryptography Goes a Long Way” was published in APS Physics.
The researchers note that, while the potential of Quantum Key Distribution (QKD) to provide unconditional secure communication between two distant parties is undisputed, its feasibility has been questioned due to certain limitations in the practical application of real-life QKD systems. The new method is seen as an important step toward practical, operational QKD networks.
Quantum Key Distribution permits securely sharing keys for one-time pad (OTP) cryptography. OTP encryption is mathematically guaranteed to be unbreakable, but only if the keys are not compromised. Therefore, secure key transmission and storage is the main challenge for ultra-secure OTP cryptography. But quantum entanglement – long-range instant correlations between photons – can be used to establish a shared key in such a way as to permit detecting any attempt to eavesdrop on the key. Therefore, quantum encryption offers complete, invulnerable security based on the laws of fundamental physics.
Quantum computing, a complementary quantum technology, first proposed by Nobel laureate Richard P. Feynman in 1982 (see also Feynman’s Lectures on Computation), could in the future permit cracking all traditional encryption schemes with sophisticated algorithms and superior computing power. But quantum encryption is invulnerable to quantum computing attacks.
Toward fast, Secure, Unbreakable Wide Area Quantum Encryption Network
MDIQKD – a quantum cryptography protocol first proposed in 2012 – tolerates relatively inefficient photon detectors and permits improving the security of quantum communication by using “decoy” photons to detect eavesdropping attacks. The researchers sent infrared photons through optical fibers with lengths between 102 and 404 km, and demonstrated security up to the longest distance.
“Measurement-device-independent quantum key distribution (MDIQKD) with the decoy-state method negates security threats of both the imperfect single-photon source and detection losses,” reads the paper’s abstract. “Lengthening the distance and improving the key rate of quantum key distribution (QKD) are vital issues in practical applications of QKD. Herein, we report the results of MDIQKD over 404 km of ultralow-loss optical fiber and 311 km of a standard optical fiber while employing an optimized four-intensity decoy-state method.”
MDIQKD had proven very slow so far, compared to the requirements for practical QKD. “The best demonstration so far sent information over a distance of 200 kilometers at a data rate of just 0.018 bits per second,” noted a MIT Technology Review commentary to a draft version of the paper. “At this rate, perfectly secure quantum cryptography would never be practical.” But now the Chinese scientists have achieved a very significant increase in speed compared to previous results.
"In addition to the long transmission distances, our system generates a 1.38 kbits per second secure finite key at 102 km, therefore constituting a strong candidate for a metropolitan quantum network with an unreliable relay"
The scientists added that system performance could be further improved by increasing the system clock rate and the efficiency of the photon detectors.
Physicists at Corning Inc., a research company headquartered in Corning, New York, and specialized in materials science and optical physics, have participated in the research. Among them, fiber optics and quantum communication specialist Daniel Nolan.
But it appears that China is pursuing a government-supported, well-funded quantum technology development effort for both civilian and military applications, ranging from unbreakable encrypted communication networks to combat support operations, more aggressively than the US. Early results of China’s quantum technology program are the world’s first quantum satellite and a “quantum radar” able to detect stealth planes 100km away, both recently covered by Hacked.
https://hacked.com/chinese-physicists-achieve-record-breaking-quantum-cryptography-breakthrough/
艹艹艹
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https://www.rt.com/news/367549-china-quantum-communication-line/
China launches world’s longest super-secure quantum communication line
Published time: 20 Nov, 2016 11:33
Get short URL
© Jose Miguel Gomez / Reuters
China has launched a quantum communication line 712 kilometers in length that is meant to safely transmit sensitive information. It is expected to be extended to 2,000 kilometers soon.
The line connecting Hefei, the capital of Anhui Province, and Shanghai, a coastal trade hub, has 11 trusted nodes along its length, Xinhua news agency reported on Sunday.
It transmitted a secure video conference between the two cities in one of its first test communications.
The line, already three years in the making and yet to be finished, will ultimately connect Shanghai to China’s capital, Beijing, and run through another major city, Jinan, with a total of 32 relay points. The entire project was expected to be finished in November, but the completion date has been moved back until at least the end of the year.
Quantum communication uses quantum entanglement of photons to ensure that nobody taps into the line, as doing so would inevitably corrupt the signal. The relay nodes are weak points, because the information is translated back into regular form there before being re-entangled and sent further along the optic fiber link.
The Chinese network is valuable for both research on how the technology can be used, and practical purposes, such as delivering secure messages between the connected cities.
China has already launched a quantum communication satellite that will eventually be connected to the Shanghai-Beijing line via a station in Beijing.
China launches world’s longest super-secure quantum communication line
Published time: 20 Nov, 2016 11:33
Get short URL
© Jose Miguel Gomez / Reuters
China has launched a quantum communication line 712 kilometers in length that is meant to safely transmit sensitive information. It is expected to be extended to 2,000 kilometers soon.
The line connecting Hefei, the capital of Anhui Province, and Shanghai, a coastal trade hub, has 11 trusted nodes along its length, Xinhua news agency reported on Sunday.
It transmitted a secure video conference between the two cities in one of its first test communications.
The line, already three years in the making and yet to be finished, will ultimately connect Shanghai to China’s capital, Beijing, and run through another major city, Jinan, with a total of 32 relay points. The entire project was expected to be finished in November, but the completion date has been moved back until at least the end of the year.
Quantum communication uses quantum entanglement of photons to ensure that nobody taps into the line, as doing so would inevitably corrupt the signal. The relay nodes are weak points, because the information is translated back into regular form there before being re-entangled and sent further along the optic fiber link.
The Chinese network is valuable for both research on how the technology can be used, and practical purposes, such as delivering secure messages between the connected cities.
China has already launched a quantum communication satellite that will eventually be connected to the Shanghai-Beijing line via a station in Beijing.
Star Expedition
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We can earn lots of money now
cirr
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Can China’s quantum radar become even more powerful? Scientists may have found the key
Experiment may extend range of systems that detect stealth aircraft, but Tsinghua physicist warns it could just be a ‘mathematical illusion’
PUBLISHED : Thursday, 15 December, 2016, 1:32pm
UPDATED : Thursday, 15 December, 2016, 10:02pm
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 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.”
http://www.scmp.com/news/china/arti...cientists-show-how-extend-range-quantum-radar
Experiment may extend range of systems that detect stealth aircraft, but Tsinghua physicist warns it could just be a ‘mathematical illusion’
PUBLISHED : Thursday, 15 December, 2016, 1:32pm
UPDATED : Thursday, 15 December, 2016, 10:02pm
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 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.”
http://www.scmp.com/news/china/arti...cientists-show-how-extend-range-quantum-radar
Nan Yang
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Chinese scientists solve quantum communication’s ‘nocturnal curse’, allowing sending of secure messages 24/7
Using photons with a longer wavelength makes long-distance transmission possible during daylight hours
STEPHEN CHEN
BINGLIN.CHEN@SCMP.COM
PUBLISHED : Tuesday, 03 January, 2017, 10:25am
UPDATED : Tuesday, 03 January, 2017, 9:36pm
UPDATED : Tuesday, 03 January, 2017, 9:36pm
Professor Pan Jianwei delivers a lecture at Hong Kong University of Science and Technology in September. Photo: Dickson Lee
A breakthrough by Chinese quantum satellite researchers could pave the way for a “constellation” of hack-proof satellites capable of transmitting secure messages 24 hours a day.
In a recent ground-based experiment on Qinghai Lake, in northwestern China, they found a solution to the “nocturnal curse” that had restricted quantum satellite activities to nighttime.
The researchers, from the University of Science and Technology of China (USTC) in Hefei, Anhui province, beamed single photons carrying quantum information over a distance of 53km during daylight hours, several times longer than the previous daytime record and with unprecedented signal quality.
“Our work proves the feasibility of a low-Earth-orbit quantum satellite constellation which works mostly in the daylight,” the researchers, led by Professor Pan Jianwei, said in a draft paper released on the website arXiv.org earlier.
The quantum satellite constellation would help China build a “global-scale quantum communication network”, they added.
Professor Pan Jianwei demonstrates quantum communication in Shanghai in May. Photo: Xinhua
Pan’s team developed the world’s first quantum satellite, Micius, which was launched into orbit in August. It was designed to use the laws of quantum physics to achieve unbreakable communication, and China, intrigued by the military and economic potential, invested heavily in the technology.
Micius uses photons in various quantum states to transmit encrypted information. But such photons are almost invisible in daylight, with the useful signals lost in background noise. That meant the satellite has only been able to operate at night, and it could take up to three days to transmit a message from Beijing to the Chinese embassy in Washington.
The USTC team solved the problem by tweaking the photon’s wavelength.
Light’s behaviour can be described either as a particle or a wave. Human eyes can see light with wavelengths of between 400 and 700 nanometres, with most of the light produced by the sun falling within that range.
The wavelength of existing quantum communication technology falls between 700 and 800nm, very close to visible light and easily affected by natural light pollution.
Pan’s team developed a new system to produce and detect photons with a wavelength of 1,550nm.
The intensity of sunlight at 1,550nm is about five times weaker than at 800nm, which allowed the researchers to reduce the background noise to a very low level – only about 3 per cent of that experienced in earlier experiments.
More...
http://m.scmp.com/news/china/articl...antum-communications-nocturnal-curse-allowing
Using photons with a longer wavelength makes long-distance transmission possible during daylight hours
STEPHEN CHEN
BINGLIN.CHEN@SCMP.COM
PUBLISHED : Tuesday, 03 January, 2017, 10:25am
UPDATED : Tuesday, 03 January, 2017, 9:36pm
UPDATED : Tuesday, 03 January, 2017, 9:36pm
Professor Pan Jianwei delivers a lecture at Hong Kong University of Science and Technology in September. Photo: Dickson Lee
A breakthrough by Chinese quantum satellite researchers could pave the way for a “constellation” of hack-proof satellites capable of transmitting secure messages 24 hours a day.
In a recent ground-based experiment on Qinghai Lake, in northwestern China, they found a solution to the “nocturnal curse” that had restricted quantum satellite activities to nighttime.
The researchers, from the University of Science and Technology of China (USTC) in Hefei, Anhui province, beamed single photons carrying quantum information over a distance of 53km during daylight hours, several times longer than the previous daytime record and with unprecedented signal quality.
“Our work proves the feasibility of a low-Earth-orbit quantum satellite constellation which works mostly in the daylight,” the researchers, led by Professor Pan Jianwei, said in a draft paper released on the website arXiv.org earlier.
The quantum satellite constellation would help China build a “global-scale quantum communication network”, they added.
Professor Pan Jianwei demonstrates quantum communication in Shanghai in May. Photo: Xinhua
Pan’s team developed the world’s first quantum satellite, Micius, which was launched into orbit in August. It was designed to use the laws of quantum physics to achieve unbreakable communication, and China, intrigued by the military and economic potential, invested heavily in the technology.
Micius uses photons in various quantum states to transmit encrypted information. But such photons are almost invisible in daylight, with the useful signals lost in background noise. That meant the satellite has only been able to operate at night, and it could take up to three days to transmit a message from Beijing to the Chinese embassy in Washington.
The USTC team solved the problem by tweaking the photon’s wavelength.
Light’s behaviour can be described either as a particle or a wave. Human eyes can see light with wavelengths of between 400 and 700 nanometres, with most of the light produced by the sun falling within that range.
The wavelength of existing quantum communication technology falls between 700 and 800nm, very close to visible light and easily affected by natural light pollution.
Pan’s team developed a new system to produce and detect photons with a wavelength of 1,550nm.
The intensity of sunlight at 1,550nm is about five times weaker than at 800nm, which allowed the researchers to reduce the background noise to a very low level – only about 3 per cent of that experienced in earlier experiments.
More...
http://m.scmp.com/news/china/articl...antum-communications-nocturnal-curse-allowing
onebyone
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Safe technology: Quantum communication goes commercial in China
TECH & SCI
By Gong Zhe
2017-03-11 22:43:50
China has built the first commercial quantum communication trunk line linking Shanghai Municipality and the eastern city of Hangzhou with uncompromised safety.
The line, named "Shanghai-Hangzhou Quantum Communication Commercial Trunk Line," is 260 kilometers long, with a price tag of nearly 25 million US dollars. It was built with absolute safety in mind.
"The line uses photons to carry information, which cannot be divided. The quantum status of these photons cannot be cloned, either. Thus there is just no way to wiretap the communication through our line," said Qian Xin, Vice President of Hangzhou Shenzhou Quantum Communication Technology Co. Ltd., the company behind the project.
A researcher from the Chinese Academy of Sciences (CAS) explains why quantum communication is safe at the World Internet Conference in eastern China's Wuzhen on November 16, 2017. /CFP Photo
Qian also said the operators of the line are trying to connect local government, banks and enterprises to the network.
The line is part of a larger project that links Shanghai directly to Beijing, which will be about 1,200 kilometers in length -- nearly five times longer than the current one.
China's Ministry of Industry and Information Technology praised the construction of the line as the start of the commercial use of quantum communication across the world.
Quantum communication is one of the major goals of China's technological advancement in this and the next decade. China's Minister of Science and Technology Wan Gang reiterated the importance of this cutting-edge technology in a press conference on Saturday.
He announced that the country will launch all 15 of its major science innovation projects, including the manufacturing of advanced quantum computers, this year.
https://news.cgtn.com/news/3d59444e316b6a4d/share_p.html?t=1489243431125
TECH & SCI
By Gong Zhe
2017-03-11 22:43:50
China has built the first commercial quantum communication trunk line linking Shanghai Municipality and the eastern city of Hangzhou with uncompromised safety.
The line, named "Shanghai-Hangzhou Quantum Communication Commercial Trunk Line," is 260 kilometers long, with a price tag of nearly 25 million US dollars. It was built with absolute safety in mind.
"The line uses photons to carry information, which cannot be divided. The quantum status of these photons cannot be cloned, either. Thus there is just no way to wiretap the communication through our line," said Qian Xin, Vice President of Hangzhou Shenzhou Quantum Communication Technology Co. Ltd., the company behind the project.
A researcher from the Chinese Academy of Sciences (CAS) explains why quantum communication is safe at the World Internet Conference in eastern China's Wuzhen on November 16, 2017. /CFP Photo
Qian also said the operators of the line are trying to connect local government, banks and enterprises to the network.
The line is part of a larger project that links Shanghai directly to Beijing, which will be about 1,200 kilometers in length -- nearly five times longer than the current one.
China's Ministry of Industry and Information Technology praised the construction of the line as the start of the commercial use of quantum communication across the world.
Quantum communication is one of the major goals of China's technological advancement in this and the next decade. China's Minister of Science and Technology Wan Gang reiterated the importance of this cutting-edge technology in a press conference on Saturday.
He announced that the country will launch all 15 of its major science innovation projects, including the manufacturing of advanced quantum computers, this year.
https://news.cgtn.com/news/3d59444e316b6a4d/share_p.html?t=1489243431125
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