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

[JSCh]

New quantum communication landline connecting East, Central China put into service
By Cao Siqi in Wuhan Source:Global Times Published: 2018/11/13 19:03:39

Screenshot shows an extension quantum communication landline connecting East China's Anhui Province and Central China's Hubei Province.Photo: Cao Siqi/GT

An extension quantum communication landline connecting East China's Anhui Province and Central China's Hubei Province was put into service on Tuesday, marking a significant milestone in China's quantum infrastructure construction that scientists say makes China the new leader in quantum communication.

The Wuhan-Hefei landline was launched on Tuesday at the Third Optics Valley Aerospace Laser and Quantum Technology International Forum hosted by China Aerospace Science and Industry Corporation, the network's major builder.

The company, which primarily develops and produces missiles and carrier rockets and also invests heavily in laser technologies and weapons, said the network is now connected to the world's first quantum communication landline opened between Beijing and Shanghai in September 2017.

Quantum communications feature ultra-high security. Information running through it is difficult to tap, intercept or crack, experts said.

An insider who declined to be named told the Global Times that the quantum communication network plays a crucial role in military operations in the information age.

"In future combat, the competition lies in the speed of transferring information. The network could help transmit classified information to the command center and then quickly instruct a combat unit," he said.

"It is fast and free from outside disturbances," he noted.

China's quantum communication ground network is connected to the world's first quantum satellite launched by China in August 2016.

The satellite is called "Micius," after a 400 BC Chinese philosopher and scientist credited as the first person to conduct optical experiments.

The company said the network can be used not only for confidential military and national defense communications but also for financial and energy purposes and other government fields.

Meanwhile, it is also expected to be used in civil communications such as on mobile phones and networks, Wu said.

According to the company, the new quantum communication landline will build 11 stations in cities in Anhui and Hubei provinces, and is 609 kilometers long.

 

[JSCh]

Letter | Published: 21 January 2019
Entanglement of three quantum memories via interference of three single photons

• Bo Jing,
• Xu-Jie Wang,
• Yong Yu,
• Peng-Fei Sun,
• Yan Jiang,
• Sheng-Jun Yang,
• Wen-Hao Jiang,
• Xi-Yu Luo,
• Jun Zhang,
• Xiao Jiang,
• Xiao-Hui Bao &
• Jian-Wei Pan

Nature Photonics (2019)

Abstract
Quantum memory networks as an intermediate stage in the development of a quantum internet1 will enable a number of significant applications2,3,4,5. To connect and entangle remote quantum memories, it is best to use photons. In previous experiments6,7,8,9,10,11,12,13, entanglement of two memory nodes has been achieved via photon interference. Going beyond the state of the art by entangling many quantum nodes at a distance is highly sought after. Here, we report the entanglement of three remote quantum memories via three-photon interference. We employ laser-cooled atomic ensembles and make use of a ring cavity to enhance the overall efficiency of our memory–photon entanglement. By interfering three single photons from three separate set-ups, we create entanglement of three memories and three photons. Then, by measuring the photons and applying feed-forward, we achieve heralded entanglement between the three memories. Our experiment may be employed as a building block to construct larger and complex quantum networks14,15.​

Entanglement of three quantum memories via interference of three single photons | Nature Photonics

 

[JSCh]

Letter | Published: 21 January 2019
Entanglement of three quantum memories via interference of three single photons

• Bo Jing,
• Xu-Jie Wang,
• Yong Yu,
• Peng-Fei Sun,
• Yan Jiang,
• Sheng-Jun Yang,
• Wen-Hao Jiang,
• Xi-Yu Luo,
• Jun Zhang,
• Xiao Jiang,
• Xiao-Hui Bao &
• Jian-Wei Pan

Nature Photonics (2019)

Abstract
Quantum memory networks as an intermediate stage in the development of a quantum internet1 will enable a number of significant applications2,3,4,5. To connect and entangle remote quantum memories, it is best to use photons. In previous experiments6,7,8,9,10,11,12,13, entanglement of two memory nodes has been achieved via photon interference. Going beyond the state of the art by entangling many quantum nodes at a distance is highly sought after. Here, we report the entanglement of three remote quantum memories via three-photon interference. We employ laser-cooled atomic ensembles and make use of a ring cavity to enhance the overall efficiency of our memory–photon entanglement. By interfering three single photons from three separate set-ups, we create entanglement of three memories and three photons. Then, by measuring the photons and applying feed-forward, we achieve heralded entanglement between the three memories. Our experiment may be employed as a building block to construct larger and complex quantum networks14,15.​

Entanglement of three quantum memories via interference of three single photons | Nature Photonics

USTC Achieves Entanglement of Three Quantum Memories via Three-Photon Interference
Jan 31, 2019

In a study published in Nature Photonics, Prof. PAN Jianwei and Prof. BAO Xiaohui at the University of Science and Technology of China (USTC) of Chinese Academy of Sciences realized the entanglement of three remote atomic-ensemble quantum memories via interference of three single photons, which paves a way towards long-distance quantum networks and multi-party quantum communication.

As an intermediate stage of quantum internet development, quantum memory networks are distinguished by the capability of the end nodes to have local memory while simultaneously allowing universal local control. This will enable a number of significant applications such as quantum teleportation and distributed quantum computing.

The most promising approach to build quantum networks is using an architecture combining photons as flying qubits with stationary matter-based quantum memories. A crucial requirement for the matter system is the ability to entangle with photons efficiently.

To improve the efficiency, Prof. PAN and Prof. BAO's group made use of a ring cavity to enhance the light-matter interaction and managed to use the ring cavity itself as a frequency filter to eliminate noise photons, which avoids unwanted losses comparing to frequently-used external frequency filters.

In addition, they use a Hermite-Gaussian mode for the cavity locking beam, which reduces its leakage into the single-photon channels significantly.

By harnessing the high-performance light-matter interface (Nat. Photon. 10, 381, 2016) and Rydberg blockade (Phys. Rev. Lett. 117, 180501, 2016), the node number can hopefully be further increased. Extension of distances for memory separations can be realized by converting photon wavelength to the telecom band and using low-loss fibre for transmission.

This work was supported by National Key R&D Program of China, Anhui Initiative in Quantum Information Technologies, National Natural Science Foundation of China and the Chinese Academy of Sciences.


USTC Achieves Entanglement of Three Quantum Memories via Three-Photon Interference---Chinese Academy of Sciences

 

[TaiShang]

China's quantum communication satellite to extend working lifetime by two yrs: scientist

(Xinhua) 14:40, February 15, 2019


WASHINGTON, Feb. 14 (Xinhua) -- A Chinese researcher said China's satellite Quantum Experiments at Space Scale (QUESS) or Micius would work at least two more years beyond its two-year working lifetime and carry out more international cooperation.

Yin Juan, a member of the QUESS team who received the annual Newcomb Cleveland Prize in Washington on Thursday night said so in an interview with Xinhua.

In the next two years, the QUESS team is expected to have the inter-continental quantum key distribution experiments with those from Italy, Russia and South Korea.

"We are open to international cooperation," said Yin, a professor of the University of Science and Technology of China. A team of 34 Chinese physicists led by Pan Jianwei with the university won the annual award that honors the most impactful research paper published in the journal Science.

The paper published in the journal Science in June 2017 reported the experiment that sends entangled photon pairs through the near-vacuum of space, measuring the quantum keys at receiving stations over 1,200 km apart.

Quantum key distribution (QKD), quantum entanglement distribution and quantum teleportation are three major scientific tasks done by QUESS, Yin said.

Based on the QKD technology, Chinese researchers could launch three more small-size satellites in the next three to five years to form a network that can fulfill more quantum communication tasks, a critical step to create the infrastructure of a globalized quantum internet one day, said Yin.

The QUESS team won the prize delivered by the American Association for the Advancement of Science as it laid the groundwork for ultra-secure communication networks of the future.

 

[JSCh]

Global First Quantum-Enabled Satellite Achieves Data Safety Goals Faster Than Expected
QIAN TONGXIN
DATE : MAR 12 2019/SOURCE : YICAI

Global First Quantum-Enabled Satellite Achieves Data Safety Goals Faster Than Expected​

(Yicai Global) March 12 -- The world's first quantum-enabled satellite Quantum Experiments at Space Scale has performed better than expected. The space station has a goal to make data privacy between different continents much safer.

QESS, nicknamed Micius or Mozi after the ancient Chinese philosopher, has reached a level of prowess that was anticipated to take two years, in just two to three months, Pan Jianwei, a quantum physics professor and an academician at Chinese Academy of Sciences, told Yicai Global. He was speaking at the ongoing top-level political conference of Two Sessions.

Communication safety is important not only to the nation but also to individuals, Pan noted. Researchers are striving to expand the coverage of quantum information technology, he said, adding that after reducing costs, it can benefit the public.

Since the launch in August 2016, Mozi achieved the global first space-ground integrated quantum communication network after one year of service.

The nation plans to develop a medium earth orbit satellite that can work around the clock to apply Mozi's findings as soon as possible, Pan said. The space station can only work at night in order to avoid solar background noise.

The satellite is primarily made for research and not for commercial use, Pan said, adding that it has increased the number of encryption keys by 40 times in the past two years so that about 400,000 encrypted quantum keys can be transmitted within one second.

Those 400,000 encryption keys can convey 40 kilobytes of data every second, Zhang Wenzhuo, an associate research fellow at the University of Science and Technology of China, told Yicai Global. The more keys, the larger the potential for commercial use, he added.

 

[Galactic Penguin SST]

Global First Quantum-Enabled Satellite Achieves Data Safety Goals Faster Than Expected
QIAN TONGXIN
DATE : MAR 12 2019/SOURCE : YICAI

Global First Quantum-Enabled Satellite Achieves Data Safety Goals Faster Than Expected​

(Yicai Global) March 12 -- The world's first quantum-enabled satellite Quantum Experiments at Space Scale has performed better than expected. The space station has a goal to make data privacy between different continents much safer.

QESS, nicknamed Micius or Mozi after the ancient Chinese philosopher, has reached a level of prowess that was anticipated to take two years, in just two to three months, Pan Jianwei, a quantum physics professor and an academician at Chinese Academy of Sciences, told Yicai Global. He was speaking at the ongoing top-level political conference of Two Sessions.

Communication safety is important not only to the nation but also to individuals, Pan noted. Researchers are striving to expand the coverage of quantum information technology, he said, adding that after reducing costs, it can benefit the public.

Since the launch in August 2016, Mozi achieved the global first space-ground integrated quantum communication network after one year of service.

The nation plans to develop a medium earth orbit satellite that can work around the clock to apply Mozi's findings as soon as possible, Pan said. The space station can only work at night in order to avoid solar background noise.

The satellite is primarily made for research and not for commercial use, Pan said, adding that it has increased the number of encryption keys by 40 times in the past two years so that about 400,000 encrypted quantum keys can be transmitted within one second.

Those 400,000 encryption keys can convey 40 kilobytes of data every second, Zhang Wenzhuo, an associate research fellow at the University of Science and Technology of China, told Yicai Global. The more keys, the larger the potential for commercial use, he added.

Alas, as we suspected, quantum encryption turns out to be another hollow hoax!

Quantum encryption surprises: Shanghai Jiaotong University team penetrated the "strongest encryption shield", the experimental success rate was as high as 60%!

量子加密惊现破绽：上海交大团队击穿“最强加密之盾”，实验成功率竟高达60%！

2019-3-12 13:24

今日，一篇在预印本 arXiv 上发表的文章显示，上海交通大学研究团队近來在经过不断的实验与尝试之后，发现了现有量子加密技术可能隐藏着极为重大的缺陷，攻破这个最强的加密之盾却不需要什么神兵利器，而是利用“盾”本身就存在的物理缺陷。这个研究这将可能导致量子加密从原本印象中的坚不可破，转而变成脆弱不堪。

因为，以上海交通大学团队所发表的研究来看，上海交通大学的研究人员们成功发现目前被广泛应用在量子通信中的 QKD（Quantum Key Distribution，量子密钥分发）方法并不完美，研究团队通过将具有不同种子频率的光子注入激光腔 ( lasing cavity) 来改变激光频率的方法，进而观察注入光子的半导体激光器的动态，最终居然获得高达 60％的信息盗取成功率。


http://www.lianmenhu.com/blockchain-9355-1
​

Commentary

As previously correctly assessed, quantum encryption is unsafe as it could anyway be hacked by targeting terminal hardware.

Therefore the real potential of this technology, if not secured, lies in the speed, allowing supraluminal communication in outer space, and making it "instantaneous" instead of the 3 to 21 minutes from Mars to Earth, 33 to 53 minutes from Jupiter and 5 hours from Pluto.

More below:

China's Deep Space Quantum Communications Capability V1.1
https://defence.pk/pdf/threads/chin...ons-news-updates.464793/page-53#post-11188985

 

[Menthol]

So basically Quantum Communication have been breached.

Its not as safe as the theory said.

I think the science community in China is still in early day, as China tend to boosting it without checking it more further. They are too focusing on achievement and then almost never thought the other implications that follow later.

 

[JSCh]

There’s a new way to break quantum cryptography - MIT Technology Review

The attacks have ruthlessly exploited imperfections in the equipment used to send quantum information. In doing so, hackers have shown that even if the laws of physics offer perfect security, equipment can never be perfect. And these imperfections create loopholes that can be exploited.

Also see,

Device-independent quantum cryptography - Wikipedia

And also,

PUBLIC RELEASE: 10-OCT-2018
Measurement-device-independent quantum communication without encryption
SCIENCE CHINA PRESS

​

Illustration of the MDI-QSDC protocol. CREDIT: ©Science China Press

Confidential communication is vital in modern society. Quantum secure direct communication is a new kind of secure communication with no encryption. In a classical secure communication, the sender and the receiver have to share a secret key in advance, then a plaintext is encoded into ciphertext, and sent to receiver through a classical channel. The ciphertext is then decoded to plaintext by receiver to complete the communication. In this structure, there exist three potential security loopholes, which are: (1) loss of key during the distribution process; (2) loss of key in storage and management; (3) interception of ciphertext by Eve for later cryptanalysis. With the development of supercomputers and quantum computers, these threats become more and more serious.

Quantum communication whose security is guarded by quantum physics principles is an important scheme resists these attacks. Quantum secure direct communication (QSDC) is a unique in its kind of secure communication, which does not require key distribution, key storage and management, and does not use ciphertext. It eliminates the three loopholes in classical secure communication efficiently.

The key problem of practical QSDC is that apparatuses used in practical quantum communication system have some defects, and these imperfections, especially defects in the measurement devices, can lead to leakage of information and affect the security of practical QSDC. Recently, a research team led by Prof. Gui-Lu Long from Tsinghua University proposed a measurement- device- independent (MDI) QSDC protocol using Einstein-Podolsky-Rosen pairs. This protocol eliminates all loopholes related to measurement devices, overcoming a key obstacle of practical QSDC. Besides, the MDI-QSDC has a twice communication distance, and a high communication capacity.


Measurement-device-independent quantum communication without encryption | EurekAlert! Science News

Peng-Hao Niu, Zeng-Rong Zhou, Zai-Sheng Lin, Yu-Bo Sheng, Liu-Guo Yin, and Gui-Lu Long. Measurement-Device-Independent Quantum Communication without Encryption, Science Bulletin (2018), DOI: doi.org/10.1016/j.scib.2018.09.009​

 

[Menthol]

There’s a new way to break quantum cryptography - MIT Technology Review


Also see,

Device-independent quantum cryptography - Wikipedia

And also,

I understand now, its in the device.

 

[TaiShang]

How do you teach a 1-year-old quantum physics?

By ZHANG ZHOUXIANG | China Daily | Updated: 2019-04-06

One-year-old Zhang Junyao reads a book beside her small bookshelf. Photo by Wang Jingjing / For China Daily

Like most fathers, I have kept up the habit of buying cartoon books for my baby girl, who is now one year old, to encourage her to develop an interest in the outside world.

However, as I opened a new box of books last week, I thought I had placed the wrong order. On the cover of the first book the boldly colored headline jumped out: Quantum Physics. The second book I picked up was titled Quarks. The third one, Aerospace Engineering, looked a little more practical at first glance. However, it was only after much closer examination of the cover that I found two much smaller words prefixing each of the headlines: Baby Loves.

Wow! Do the authors of the books expect a 1-year-old girl to learn what her father did not study until the third year of university? How could I explain such complex concepts as, say, superposition states, to my 1-year-old daughter?

Yet, as I started this "mission impossible", I soon realized it might not be as difficult as I first thought. The quantum physics book is, like all the books I buy for her, still a cartoon book, containing very few words.

Open the first page and you see a baby running after a cat, drawn in a simple, colorful style that every infant will fall in love with at first sight.

Then the story became faster-paced. The cat jumped into a box and the box shut automatically. The baby sat next to the closed box, not knowing what his furry friend was doing inside.

"Is the cat asleep or awake?" A question emerged from the book, with the answer on the next page: "It can be both and in quantum physics. We call it a superposition state of being asleep and awake. When the baby opens the box, the superposition becomes a sure position."

Having been taught the whole thing with interest by me, my daughter picked up our dog and tried to undertake a similar experiment, which I fortunately, managed to stop in time. I am pretty sure she still knows little about quantum physics and won't understand the concept behind it for at least another decade.

However, at least she has been told the story and will find it of interest when the teacher mentions it in class.

More importantly, for her, physics won't be the boring subject that many consider it to be. It won't be full of concepts that perplex her mind, but of funny stories that she's glad to hear about.

And this is the direction that all primary education institutions should be looking to take.

As a result of the accumulated wisdom of the top thinkers over the centuries, natural science is a really difficult subject to learn for those without a strong interest in it. The more quantum physics books that are tailored toward infants, the more children will develop an appetite for the subject in their early years.

More importantly, these science books are written in a way that most young children can understand. Inste ad of throwing a complicated concept at the infant reader, it puts everything into a small story that the reader can enjoy with the help of their parents.

Honestly speaking, I would have preferred my quantum physics textbooks in university to have been written in this way, instead of the traditional way. Maybe I could have attained higher marks if my professor had brought a cat into the classroom to explain Schrodinger's thought experiment using an actual cat, instead of simply telling me about it.

But the idea of making science interesting doesn't just apply to children's education. A survey by the Chinese Association for Science and Technology found that only about 3.3 percent of China's total population have a basic knowledge of natural science, compared to figure of over 10 percent who do in developed countries. A key reason for that, according to experts, is the lack of proper scientific learning materials, especially those for adults.

This in turn explains, at least in part, why Chinese engineers have been faring better than Chinese scientists. A certain proportion of the population with a good understanding of natural science should be the basis for a nation to produce large numbers of excellent scientists, which in turn will render firm support to the prosperity of the nation.

Having finished the book on quantum physics, I made a thorough check of my daughter's little bookshelf and divided her books into a few different categories. The topics of the books ranged from dinosaurs to animal tongues, then to everyday wisdom, yet they all had one thing in common: They were interesting.

Dinosaurs

Besides the Baby Loves Quantum Physics book, there were books like How Dinosaurs Lived and Why Dogs Are Your Friends. These cartoon books tell stories just like animations, with the only difference being is that they're printed on paper, not viewed on an LED display.

In one of the books, different kinds of dinosaurs appear in both a logical and engaging order, passing along the infant protagonist to one dinosaur after another. They introduce themselves so that the reader gains a clear understanding about their names and their height, weight, favorite food, etc.

Animal tongues

In another book about the tongues of animals, the author and cartoonist not only drew different kinds of animals and their tongues in various ways, but also fixed certain materials to related parts of the animals so they feel like real ones. For example, when the reader touches the head of the camel, they feel actual camel hair. When they touch the tail of the snub-nosed monkey, they touch a small piece of cloth that's feels like a real tail.

My daughter's favorite is the tongue of the frog, made of plastic with a rough surface.

Zoo sounds

Another series of interactive books my daughter likes contain audio elements. Each of the pages is about 3 to 4 millimeters thick, with electric wires hidden inside, linking a small piece of metal to a tiny speaker and battery. When she taps the metal pad with her finger, animal sounds emanate from the page.

Flexible strips

Another book in the series is Baby Visits the Zoo. Each of the pages has flexible strips that the reader can move with their little fingers; When she finishes sliding them, the strips in their correct positions form a picture of an animal in the zoo.

Thanks to this book, my daughter has learned about the zebra, the lion, the elephant, the tiger, as well as the bonobo.

Chicks and daily behavior

Another series of books called The Polite Chickie stars a newborn chick named Qiuqiu, which means "ball" in Chinese because it resembles a furry ball. In the books, she learns how to talk with others, speak with her mummy, and how to play outside without risking falling out of her chair. She has already taken the chick around with her for company, just like our furry canine friend.

I am now planning to place an order for Baby Loves Programming for my daughter. I was a coding monkey in the lab during my university days and I hope she can have a taste of that. Happy coding!

http://www.chinadaily.com.cn/a/201904/06/WS5ca7e842a3104842260b4a03.html

 

[JSCh]

NEWS RELEASE 29-MAY-2019
Secure metropolitan quantum networks move a step closer
IOP PUBLISHING

Successful new field tests of a continuous-variable quantum key distribution (CV-QKD) system over commercial fiber networks could pave the way to its use in metropolitan areas.

That is the key achievement from a joint team of Chinese scientists, published today in Quantum Science and Technology, which demonstrates CV-QKD transmission over commercial deployed fiber link with a distance of 50 kilometres.

Team leader and lead author, Prof. Hong Guo, from a joint team of Peking University and Beijing University of Posts and Telecommunications (PKU-BUPT joint team), Beijing, said: "CV-QKD provides, in principle, unconditional secret keys to protect people's data - such as banking information, emails and passwords.

"It has attracted much attention in the past few years, because it uses standard telecom components that operate at room temperature, instead of specific quantum devices such as single photon detectors etc, and it has potentially much higher secret key rates. However, most previous long-distance CV-QKD demonstrations were only done in laboratory fiber, without the disturbances caused by the field environment."

Lead authors Dr. Yichen Zhang and Prof. Song Yu, from the PKU-BUPT joint team, Beijing, said: "There are several challenges to bringing a practical CV-QKD system from a laboratory setup to the real world. Deployed commercial dark fibers are inevitably subject to much stronger perturbations from changing environmental conditions and physical stress. This in turn causes severe disturbances of the transmitted quantum states.

"They also suffer from higher losses due to splices, sharp bends and inter-fiber couplings. The software and hardware of CV-QKD modules must not only be designed to cope with all the conditions affecting the transmission fiber, but must also be robustly engineered to operate in premises designed for standard telecom equipment. Furthermore, as the systems need to run continuously and without frequent attention, they need to be designed to automatically recover from any errors and shield end users from service interruptions."

The PKU-BUPT joint research team carried out two field tests of CV-QKD over commercial fiber networks in two cities of China - Xi'an and Guangzhou - achieving transmission distances of 30.02 km (12.48 dB loss) and 49.85 km (11.62 dB loss), respectively.

Prof. Hong Guo said: "The longest previous field tests of a CV-QKD system were over a 17.52 km deployed fiber (10.25 dB loss) and a 17.7 km deployed fiber (5.6 dB loss), where the secret key rates were 0.2 kbps and 0.3 kbps, respectively.

"Comparing with these results, our results show a more than twice transmission distance, and a two orders-of-magnitude higher secret key rates, though in more lossy commercial fiber links.

"This is a significant step in bringing CV-QKD closer to everyday use. It has pushed CV-QKD towards a more practical setting, and, naturally, one may expect that a quantum-guaranteed secure metropolitan network could be built within reach of current technologies."


Secure metropolitan quantum networks move a step closer | EurekAlert! Science News

 

[JSCh]

Beating the Fundamental Rate-Distance Limit in a Proof-of-Principle Quantum Key Distribution System
Shuang Wang, De-Yong He, Zhen-Qiang Yin, Feng-Yu Lu, Chao-Han Cui, Wei Chen, Zheng Zhou, Guang-Can Guo, and Zheng-Fu Han

Phys. Rev. X 9, 021046 – Published 4 June 2019
DOI: https://doi.org/10.1103/PhysRevX.9.021046

POPULAR SUMMARY
Quantum key distribution (QKD), which exploits the laws of quantum physics to share encryption keys between two remote users, is a promising technology to revolutionize information security. To maximize the probability that keys are successfully transmitted across lossy fiber-optic channels, it will be necessary to boost the rate at which users share keys. However, theory indicates that, without the aid of quantum repeaters, there is a fundamental limit to how quickly keys can be shared over any given distance. We implement a QKD system that overcomes these limits, achieving a key transmission rate 3 times higher than the predicted bound across a 300-km-long optical fiber.

Our scheme is based on a recently proposed protocol known as “twin-field QKD (TF-QKD) without phase postelection.” Two users prepare pairs of weak coherent light pulses with phase and frequency locked, encode their key bits as one of two optical phases, and send the pulses to an untrusted middle station, which measures the phase difference of the pulses in each pair. To achieve stable and high-visibility single-photon interference, we compensate for the fast phase evolution of the twin pulses traveling across hundreds of kilometers of fiber channels. Finally, we confirm the feasibility of TF-QKD and its prominent superiority in real fiber channels for the first time.

Our demonstration shows that achieving a high key rate is feasible in long-distance-fiber QKD implementations, which offers a new approach to large networks.

 

[JSCh]

18 Jun 2019 | 20:00 GMT
World's First "Quantum Drone" for Impenetrable Air-to-Ground Data Links Takes Off
Chinese researchers are developing an airborne quantum communications network with drones as nodes

By Charles Q. Choi

Quantum drones under development in China could lead to nigh unhackable airborne quantum communication networks, a new study finds.


...

World's First "Quantum Drone" for Impenetrable Air-to-Ground Data Links Takes Off - IEEE Spectrum

 

[JSCh]

Article | Published: 24 June 2019

Experimental quantum repeater without quantum memory

• Zheng-Da Li,
• Rui Zhang,
• Xu-Fei Yin,
• Li-Zheng Liu,
• Yi Hu,
• Yu-Qiang Fang,
• Yue-Yang Fei,
• Xiao Jiang,
• Jun Zhang,
• Li Li,
• Nai-Le Liu,
• Feihu Xu,
• Yu-Ao Chen &
• Jian-Wei Pan

Nature Photonics (2019)

Abstract
Quantum repeaters—important components of a scalable quantum internet—enable entanglement to be distributed over long distances. The standard paradigm for a quantum repeater relies on the necessary, demanding requirement of quantum memory. Despite significant progress, the limited performance of quantum memory means that making practical quantum repeaters remains a challenge. Remarkably, a proposed all-photonic quantum repeater avoids the need for quantum memory by harnessing the graph states in the repeater nodes. Here we perform an experimental demonstration of an all-photonic quantum repeater. By manipulating a 12-photon interferometer, we implement a 2 × 2 parallel all-photonic quantum repeater, and observe an 89% enhancement of entanglement-generation rate over standard parallel entanglement swapping. These results provide a new approach to designing repeaters with efficient single-photon sources and photonic graph states, and suggest that the all-photonic scheme represents an alternative path—parallel to matter-memory-based schemes—towards realizing practical quantum repeaters.


Experimental quantum repeater without quantum memory | Nature Photonics

 

[JSCh]

First Object Teleported from Earth to Orbit - MIT Technology Review

Researchers in China have teleported a photon from the ground to a satellite orbiting more than 500 kilometers above.
by Emerging Technology from the arXiv
Jul 10, 2017

Ground-to-satellite quantum teleportation
Ji-Gang Ren, Ping Xu, Hai-Lin Yong, Liang Zhang, Sheng-Kai Liao, Juan Yin, Wei-Yue Liu, Wen-Qi Cai, Meng Yang, Li Li, Kui-Xing Yang, Xuan Han, Yong-Qiang Yao, Ji Li, Hai-Yan Wu, Song Wan, Lei Liu, Ding-Quan Liu, Yao-Wu Kuang, Zhi-Ping He, Peng Shang, Cheng Guo, Ru-Hua Zheng, Kai Tian, Zhen-Cai Zhu, Nai-Le Liu, Chao-Yang Lu, Rong Shu, Yu-Ao Chen, Cheng-Zhi Peng, Jian-Yu Wang, Jian-Wei Pan
(Submitted on 4 Jul 2017)

An arbitrary unknown quantum state cannot be precisely measured or perfectly replicated. However, quantum teleportation allows faithful transfer of unknown quantum states from one object to another over long distance, without physical travelling of the object itself. Long-distance teleportation has been recognized as a fundamental element in protocols such as large-scale quantum networks and distributed quantum computation. However, the previous teleportation experiments between distant locations were limited to a distance on the order of 100 kilometers, due to photon loss in optical fibres or terrestrial free-space channels. An outstanding open challenge for a global-scale "quantum internet" is to significantly extend the range for teleportation. A promising solution to this problem is exploiting satellite platform and space-based link, which can conveniently connect two remote points on the Earth with greatly reduced channel loss because most of the photons' propagation path is in empty space. Here, we report 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 1400 km. To optimize the link efficiency and overcome the atmospheric turbulence in the up-link, a series of techniques are developed, including a compact ultra-bright source of multi-photon entanglement, narrow beam divergence, high-bandwidth and high-accuracy acquiring, pointing, and tracking (APT). We demonstrate successful quantum teleportation for six input states in mutually unbiased bases with an average fidelity of 0.80+/-0.01, well above the classical limit. This work establishes the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward global-scale quantum internet.
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Comments: 16 pages, 3 figures

Subjects: Quantum Physics (quant-ph); Optics (physics.optics); Space Physics (physics.space-ph)
DOI: 10.1038/nature23675
Cite as: arXiv:1707.00934 [quant-ph]
(or arXiv:1707.00934v1 [quant-ph] for this version)