China Quantum Communiations Technology: Cryptography, Radar, Satellite, Teleportation, Network

[onebyone]

What ‘teleporting’ a photon to space means
Using quantum entanglement and a purpose-built satellite, first successful ‘quantum teleportation’ brings a quantum internet a step closer.

Apparatus for an entanglement experiment in a normal, non-orbital laboratory.
VOLKER STEGER / SCIENCE PHOTO LIBRARY / GETTY

A team of Chinese researchers has reported the first successful ‘quantum teleportation’ to space. Using the Micius satellite, launched in August 2016 specifically to perform such cutting-edge quantum experiments, the scientists used pairs of entangled particles to recreate exactly the properties of a photon on Earth in a photon in orbit.
Ji-Gang Ren, of the University of Science and Technology of China, and colleagues write that they have accomplished “the first quantum teleportation of independent single-photon qubits from a ground observatory to a low Earth orbit satellite—through an up-link channel – with a distance up to 1,400 km”.

Though this feat is called quantum teleportation, no actual teleportation of objects occurs. It’s a way of transmitting information about a particle; while it sounds exotic, it is routinely used in laboratories on Earth.

Entanglement is a property of particles created at the same time which exist in a shared state, such that actions affecting one particle also affect the other. This holds even when the particles are separated by a great distance.

In 1993, physicists realised entanglement could be used to effectively copy the quantum state of a particle and paste it onto another particle, making the second particle identical to the first in all respects except location. It is as if the first particle has been cloned, or teleported.

Since the teleportation copies the quantum state of the first particle exactly, it could be used to transmit qubits, the quantum bits used in quantum computation.

Given there is no physical teleportation and, as noted above, the experiment is commonly performed in ground-based labs, what’s the big deal?

First, it’s an astonishing engineering achievement to manage the required precision and sensitivity when a distant satellite moving at great speed is involved. Second, the researchers have their eyes on what comes next, and they’re thinking big: as they note, this is “the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward global-scale quantum internet”.

The paper describing the experiment has been published to the Arxiv preprint server.

https://cosmosmagazine.com/physics/chinese-scientists-teleport-a-photon-to-space

 

[!eon]

At last, one dream when i studied in university comes close to be true.

You studied at Stuttgart ?

 

[Boomin' Bomber I.J.]

Not willing to accept....

 

[El Sidd]

Teleport Jerusalem.

World peace

 

[BRAVO_]

amazing ..... when i initially red the news i thought its one more gossip but after watching so many credible sources in favor of this news at google.... i would like to congratulate the Micius team who created the first satellite-to-ground quantum network....

 

[JSCh]

Sheng-Kai Liao, Hai-Lin Yong, Chang Liu, Guo-Liang Shentu, Dong-Dong Li, Jin Lin, Hui Dai, Shuang-Qiang Zhao, Bo Li, Jian-Yu Guan, Wei Chen, Yun-Hong Gong, Yang Li, Ze-Hong Lin, Ge-Sheng Pan, Jason S. Pelc, M. M. Fejer, Wen-Zhuo Zhang, Wei-Yue Liu, Juan Yin, Ji-Gang Ren, Xiang-Bin Wang, Qiang Zhang, Cheng-Zhi Peng & Jian-Wei Pan. Long-distance free-space quantum key distribution in daylight towards inter-satellite communication. Nature Photonics (2017). DOI: 10.1038/nphoton.2017.116

Abstract
In the past, long-distance free-space quantum communication experiments could only be implemented at night. During the daytime, the bright background sunlight prohibits quantum communication in transmission under conditions of high channel loss over long distances. Here, by choosing a working wavelength of 1,550 nm and developing free-space single-mode fibre-coupling technology and ultralow-noise upconversion single-photon detectors, we have overcome the noise due to sunlight and demonstrate free-space quantum key distribution over 53 km during the day. The total channel loss is ∼48 dB, which is greater than the 40 dB channel loss between the satellite and ground and between low-Earth-orbit satellites. Our system thus demonstrates the feasibility of satellite-based quantum communication in daylight. Moreover, given that our working wavelength is located in the optical telecom band, our system is naturally compatible with ground fibre networks and thus represents an essential step towards a satellite-constellation-based global quantum network.​

 

[JSCh]

Sheng-Kai Liao, Hai-Lin Yong, Chang Liu, Guo-Liang Shentu, Dong-Dong Li, Jin Lin, Hui Dai, Shuang-Qiang Zhao, Bo Li, Jian-Yu Guan, Wei Chen, Yun-Hong Gong, Yang Li, Ze-Hong Lin, Ge-Sheng Pan, Jason S. Pelc, M. M. Fejer, Wen-Zhuo Zhang, Wei-Yue Liu, Juan Yin, Ji-Gang Ren, Xiang-Bin Wang, Qiang Zhang, Cheng-Zhi Peng & Jian-Wei Pan. Long-distance free-space quantum key distribution in daylight towards inter-satellite communication. Nature Photonics (2017). DOI: 10.1038/nphoton.2017.116

Abstract
In the past, long-distance free-space quantum communication experiments could only be implemented at night. During the daytime, the bright background sunlight prohibits quantum communication in transmission under conditions of high channel loss over long distances. Here, by choosing a working wavelength of 1,550 nm and developing free-space single-mode fibre-coupling technology and ultralow-noise upconversion single-photon detectors, we have overcome the noise due to sunlight and demonstrate free-space quantum key distribution over 53 km during the day. The total channel loss is ∼48 dB, which is greater than the 40 dB channel loss between the satellite and ground and between low-Earth-orbit satellites. Our system thus demonstrates the feasibility of satellite-based quantum communication in daylight. Moreover, given that our working wavelength is located in the optical telecom band, our system is naturally compatible with ground fibre networks and thus represents an essential step towards a satellite-constellation-based global quantum network.​

Quantum Cryptography System Breaks Daylight Distance Record
By Charles Q. Choi
Posted 24 Jul 2017 | 15:26 GMT

Illustration: Nature Photonics

Satellites can now set up quantum communications links through the air during the day instead of just at night, potentially helping a nigh-unhackable space-based quantum Internet to operate 24-7, a new study from Chinese scientists finds.

Quantum cryptography exploits the quantum properties of particles such as photons to help encrypt and decrypt messages in a theoretically unhackable way. Scientists worldwide are now endeavoring to develop satellite-based quantum communications networks for a global real-time quantum Internet.

However, prior experiments with long-distance quantum communications links through the air were mostly conducted at night because sunlight serves as a source of noise. Previously, “the maximum range for day-time free-space quantum communication was 10 kilometers,” says study co-senior author Qiang Zhang, a quantum physicist at the University of Science and Technology of China in Shanghai.

Now researchers led by quantum physicist Jian-Wei Pan at the University of Science and Technology of China at Hefei have successfully established 53-kilometer quantum cryptography links during the day between two ground stations. This research suggests that such links could work between a satellite and either a ground station or another satellite, they say.

To overcome interference from sunlight, the researchers switched from the roughly 700-to-900-nanometer wavelengths of light used in all prior day-time free-space experiments to roughly 1,550 nm. The sun is about one-fifth as bright at 1,550 nanometers as it is at 800 nanometers, and 1,550-nanometer light can also pass through Earth's atmosphere with virtually no interference. Moreover, this wavelength is also currently widely used in telecommunications, making it more compatible with existing networks.

Previous research was reluctant to use 1,550-nanometer light because of a lack of good commercial single-photon detectors capable of working at this wavelength. But the Shanghai group developed a compact single-photon detector for 1,550-nanometer light that could work at room temperature. Moreover, the scientists developed a receiver that needed less than one tenth of the field of view that receivers for night-time quantum communications links usually need to work. This limited the amount of noise from stray light by a factor of several hundred.

In experiments, the scientists repeatedly established quantum communications links across Qinghai Lake, the biggest lake in China, from 3:30 p.m. to 5 p.m. local time on several sunny days, achieving transmission rates of 20 to 400 bits per second. Furthermore, they could establish these links despite roughly 48 decibels of loss in their communications channel, which is more than the roughly 40 to 45 decibels of loss typically seen in communications channels between satellites and the ground and between low-Earth-orbit satellites, Zhang says. In comparison, previous day-time free-space quantum communications experiments could only accommodate roughly 20 decibels of noise.

The researchers note that their experiments were performed in good weather, and that quantum communication is currently not possible in bad weather with today’s technology. Still, they note that bad weather is only a problem for ground-to-space links, and that it would not pose a problem for links between satellites.

In the future, the researchers expect to boost transmission rates and distance using better single-photon detectors, perhaps superconducting ones. They may also seek to exploit the quantum phenomenon known as entanglement to carry out more sophisticated forms of quantum cryptography, although this will require generating very bright sources of entangled photons that can operate in a narrow band of wavelengths, Zhang says.

The scientists detailed their findings online 24 July in the journal Nature Photonics.


Quantum Cryptography System Breaks Daylight Distance Record - IEEE Spectrum

 

[JSCh]

Qubits can swim through seawater
Aug 25, 2017

Down periscope: could submarines use quantum encryption?​

Photon-based qubits and entangled states have been transmitted up to 3 m in sea water by Xian-Min Jin and colleagues at Shanghai Jiao Tong University and the University of Science and Technology of China. While this distance pales in comparison with the 1400 km satellite-to-ground transmission achieved earlier this year by another team in China, the ability to send quantum information through seawater is a significant challenge because the liquid medium is much more absorptive of light than air.

Photons make very good qubits (quantum bits of information) because they can travel long distances without interacting with transmission media such as an optical fibre or air. These interactions destroy quantum information and therefore at first glance water should be a poor medium for qubits because it is much more absorptive of light than optical fibres or air.

Window of opportunity
The team managed to get around this problem by using photons with wavelengths of 405 nm, which falls within the "blue-green" window in which light absorption in water is relatively low. They also worked out that encoding quantum information in the polarization states of a photon gives the qubit its best chance of surviving its watery journey. This is because seawater is isotropic and therefore there should be no strong de-polarization effects. Indeed, the team's calculations suggest that the polarization of a photon can survive multiple collisions with molecules in seawater – and any depolarization that does occur can be dealt with by filtering out the affected photons.

Jin and colleagues showed that quantum information encoded in single 405 nm photons can be transmitted 3 m with a fidelity of greater than 98%. The team also did a separate experiment involving entangled pairs of 810 nm photons. Although these photons experience about 300 times more absorption than their 405 nm counterparts, they found that quantum entanglement is preserved to a very high degree after one of the photon pair is transmitted 3 m through seawater.

Secure submarines
The transmission of qubits and quantum entanglement play roles in quantum key distribution (QKD), which uses the laws of quantum mechanics to ensure that messages can be sent securely between two parties. It could be possible, therefore, to use QKD on a submerged submarine, for example. The problem, however, is that seawater is highly absorptive of light even at 405 nm, so communicating over distances of a kilometre or more would require huge numbers of photons.

The research is described in Optics Express.


About the author
Hamish Johnston is editor of physicsworld.com


Qubits can swim through seawater - physicsworld.com

Ling Ji, Jun Gao, Ai-Lin Yang, Zhen Feng, Xiao-Feng Lin, Zhong-Gen Li, and Xian-Min Jin. Towards quantum communications in free-space seawater. Optics Express (2017). DOI: 10.1364/OE.25.019795​

 

[GS Zhou]

The Beijing to Shanghai quantum communication line completes the final tests!


国家量子保密通信“京沪干线”项目通过总技术验收
2017-09-04

2017年8月30日下午，国家量子保密通信“京沪干线”技术验证及应用示范项目技术验收评审会在中国科学技术大学举行，评审专家组听取了项目组关于项目建设基本情况和分系统验收情况的汇报，经现场质询和讨论，专家组认为项目已完成了预期的技术验证和应用示范任务，具备开通条件，同意通过技术验收。

“京沪干线”项目是2013年7月由国家发改委批复立项，由安徽省、山东省共同配套投资建设并得到了上海市、北京市的大力支持，由中科院领导、中国科学技术大学作为项目建设主体承担，中国有线电视网络有限公司、山东信息通信技术研究院、中国科大先进技术研究院、中国银行业监督管理委员会等单位协作建设。

本项目的应用示范主要合作单位有中国银行业监督管理委员会，包括由银监会统一协调和指导下的中国工商银行、中国民生银行、北京农商银行等各银行单位。

在各单位的配合下，工作人员经过42个月的艰苦努力，突破了高速量子密钥分发、高速高效率单光子探测、可信中继传输和大规模量子网络管控等系列工程化实现的关键技术，克服了施工难度大、协同协调复杂等难关，最终于2016年底顺利完成全线贯通，搭建了连接北京、济南、合肥、上海的全长2000余公里的量子保密通信骨干线路，进行了大尺度量子保密通信技术试验验证，开展了远程高清量子保密视频会议系统和其他多媒体跨域互联应用研究，完成了金融、政务领域的远程或同城数据灾备系统、金融机构数据采集系统等应用示范，在半年多时间里，一直进行着各分系统的应用测试和720小时长时间稳定性测试，测试结果表明系统的各项技术性能指标均达到了设计要求，全线路密钥率大于20kbps，可满足万用户的密钥分发业务需求。同时，京沪干线北京接入点实现与“墨子号”量子科学实验卫星兴隆地面站的连接，全线密钥率大于5kbps，已形成星地一体的广域量子通信网络雏形，大大扩展了京沪干线应用能力。

 

[Nilgiri]

The Beijing to Shanghai quantum communication line completes the final tests!


国家量子保密通信“京沪干线”项目通过总技术验收
2017-09-04

2017年8月30日下午，国家量子保密通信“京沪干线”技术验证及应用示范项目技术验收评审会在中国科学技术大学举行，评审专家组听取了项目组关于项目建设基本情况和分系统验收情况的汇报，经现场质询和讨论，专家组认为项目已完成了预期的技术验证和应用示范任务，具备开通条件，同意通过技术验收。

“京沪干线”项目是2013年7月由国家发改委批复立项，由安徽省、山东省共同配套投资建设并得到了上海市、北京市的大力支持，由中科院领导、中国科学技术大学作为项目建设主体承担，中国有线电视网络有限公司、山东信息通信技术研究院、中国科大先进技术研究院、中国银行业监督管理委员会等单位协作建设。

本项目的应用示范主要合作单位有中国银行业监督管理委员会，包括由银监会统一协调和指导下的中国工商银行、中国民生银行、北京农商银行等各银行单位。

在各单位的配合下，工作人员经过42个月的艰苦努力，突破了高速量子密钥分发、高速高效率单光子探测、可信中继传输和大规模量子网络管控等系列工程化实现的关键技术，克服了施工难度大、协同协调复杂等难关，最终于2016年底顺利完成全线贯通，搭建了连接北京、济南、合肥、上海的全长2000余公里的量子保密通信骨干线路，进行了大尺度量子保密通信技术试验验证，开展了远程高清量子保密视频会议系统和其他多媒体跨域互联应用研究，完成了金融、政务领域的远程或同城数据灾备系统、金融机构数据采集系统等应用示范，在半年多时间里，一直进行着各分系统的应用测试和720小时长时间稳定性测试，测试结果表明系统的各项技术性能指标均达到了设计要求，全线路密钥率大于20kbps，可满足万用户的密钥分发业务需求。同时，京沪干线北京接入点实现与“墨子号”量子科学实验卫星兴隆地面站的连接，全线密钥率大于5kbps，已形成星地一体的广域量子通信网络雏形，大大扩展了京沪干线应用能力。

That's awesome.

Is there something significant about 2032 as seen in the text?

 

[bobsm]

That's awesome.

Is there something significant about 2032 as seen in the text?

Total length of 2032 km.

 

[JSCh]

World’s first secure quantum communication line in China gets green light
By Zhang Huan (People's Daily Online) 17:11, September 05, 2017

The world’s first secure quantum communication line in China has passed technical inspection and is able to operate, according to the University of Science and Technology of China on Sept. 4.

The secure quantum communication line spans more than 2,000 kilometers, linking the four cities of Beijing, Jinan, Hefei, and Shanghai.

Construction of the line, approved by China’s National Development and Reform Commission in July 2013, was completed late last year after 42 months of effort in overcoming technical difficulties to achieve quantum key distribution, technology of single photon detection, and reliable data transmission.

Quantum communication is ultra-secure, as a quantum photon can neither be separated nor duplicated. Accordingly, it is impossible to wiretap, intercept, or crack the information it transmits.

China has achieved many “firsts” in the field of quantum communication, such as the world’s first secure quantum communication line connecting Beijing and Shanghai, and the first quantum communication satellite nicknamed “Micius.”

The success in building the line shows that China continues to lead the world in practical application and industrialization of quantum technology.

 

[cirr]

2016年8月，中国第一次在报道中宣布：首部基于单光子检测的量子雷达系统研制成功，实际测试工作可能在2015年底，完成了量子探测机理、目标散射特性研究以及量子探测原理的实验验证，并且在外场完成真实大气环境下目标探测试验，获得百公里级探测能力，探测灵敏度极大提高，指标均达到预期效果。

Quantum radar prototype now able to detect stealth target hundreds(notice the plural) of kms away

也许100公里级的探测能力谈不上高，但是在量子雷达领域却可以说，或许已领先了美国，目前国外最远也只有20公里。据新消息，2017年8月，中国电科十四所透露，量子雷达原理样机已能探测到数百公里外的目标，成功地通过验收，从而成为了中国首台威力突破百公里量级的量子雷达样机，且取得了白天开机工作的重大突破，这标志着中国量子雷达技术再获重大突破！

http://www.chinatimes.com/cn/realtimenews/20170907001175-260417

 

[terranMarine]

2016年8月，中国第一次在报道中宣布：首部基于单光子检测的量子雷达系统研制成功，实际测试工作可能在2015年底，完成了量子探测机理、目标散射特性研究以及量子探测原理的实验验证，并且在外场完成真实大气环境下目标探测试验，获得百公里级探测能力，探测灵敏度极大提高，指标均达到预期效果。

Quantum radar prototype now able to detect stealth target hundreds(notice the plural) of kms away

也许100公里级的探测能力谈不上高，但是在量子雷达领域却可以说，或许已领先了美国，目前国外最远也只有20公里。据新消息，2017年8月，中国电科十四所透露，量子雷达原理样机已能探测到数百公里外的目标，成功地通过验收，从而成为了中国首台威力突破百公里量级的量子雷达样机，且取得了白天开机工作的重大突破，这标志着中国量子雷达技术再获重大突破！

 

[JSCh]

China's first commercial quantum private communication network completed
Source: Xinhua| 2017-09-12 20:37:53|Editor: Xiang Bo



JINAN, Sept. 12 (Xinhua) -- China's first commercial quantum private communication network has been completed in Shandong Province, local government said Tuesday.

The network is exclusively for 242 Party and government users in the provincial capital of Jinan. Hundreds of pieces of equipment connected by hundreds of kilometers of fiber optics were installed within five months.

Based on decoy-state quantum key distribution and trusted relay groups, the network provides secure telephone and data communication services.

The network is expected to be connected to the Beijing-Shanghai quantum communication network.