For the first time, researchers have sent a quantum-secured message containing more than one bit of information per photon through the air above a city. The demonstration showed that it could one day be practical to use high-capacity, free-space quantum communication to create a highly secure link between ground-based networks and satellites, a requirement for creating a global quantum encryption network.
Other scientists have already tried quantum communications with a satellite. In June a team of Chinese physicists reports that it sent eerily intertwined quantum particles from a satellite to ground stations separated by 1200 kilometers.
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Tomi Engdahl says:
http://www.etn.fi/index.php/13-news/6750-kvanttisalattuja-bitteja-ilmateitse
https://www.uusiteknologia.fi/2017/08/31/kvanttitekniikan-4d-salaus-toimii/
Tomi Engdahl says:
World’s First “Quantum Drone” for Impenetrable Air-to-Ground Data Links Takes Off
https://spectrum.ieee.org/tech-talk/computing/networks/quantum-drone
Tomi Engdahl says:
The world’s first integrated quantum communication network
https://phys.org/news/2021-01-world-quantum-network.html
Chinese scientists have established the world’s first integrated quantum communication network, combining over 700 optical fibers on the ground with two ground-to-satellite links to achieve quantum key distribution over a total distance of 4,600 kilometers for users across the country. The team, led by Jianwei Pan, Yuao Chen, Chengzhi Peng from the University of Science and Technology of China in Hefei, reported in Nature their latest advances towards the global, practical application of such a network for future communications.
Tomi Engdahl says:
https://www.iflscience.com/physics/new-quantum-teleportation-record-broken-a-step-forward-for-quantum-internet/
Tomi Engdahl says:
Researchers realize efficient generation of high-dimensional quantum teleportation
https://phys.org/news/2021-01-efficient-high-dimensional-quantum-teleportation.html
Tomi Engdahl says:
Quantum network is step towards ultrasecure internet
Experiment connects three devices with entangled photons, demonstrating a key technique that could enable a future quantum internet.
https://www.nature.com/articles/d41586-021-00420-5
Tomi Engdahl says:
Researchers create an ‘un-hackable’ quantum network over hundreds of kilometers using optical fiber https://www.zdnet.com/article/researchers-created-an-un-hackable-quantum-network-over-hundreds-of-kilometers-using-optical-fiber/
Researchers from Toshiba have successfully sent quantum information over 600-kilometer-long optical fibers, creating a new distance record and paving the way for large-scale quantum networks that could be used to exchange information securely between cities and even countries.
Tomi Engdahl says:
“The launch is significant,” says physicist Paul Kwiat of the University of Illinois in Urbana-Champaign, because it means the Chinese are starting to build, and not just plan, a quantum network.
China’s Quantum-Encrypting Satellites Shrink, Networking Abilities Grow China starts to build QKD networks as U.S. pours millions into quantum R&D
https://spectrum.ieee.org/satellite-qkd-china?share_id=7198773&socialux=facebook&utm_campaign=RebelMouse&utm_content=IEEE+Spectrum&utm_medium=social&utm_source=facebook#toggle-gdpr
The orbiting Tiangon-2 Space Lab has transmitted quantum encryption keys to four ground stations, researchers reported on 18 August. The same network of ground stations is also able to receive quantum keys from the orbiting Micius satellite, which is in a much higher orbit, using the space station as a repeater. It comes just after the late July launch of Jinan 1, China’s second quantum-encrypting satellite, by the University of Science and Technology (UST) of China. The UST told Xinhua that the new satellite is a sixth the mass of its 2016 predecessor.
“The launch is significant,” says physicist Paul Kwiat of the University of Illinois in Urbana-Champaign, because it means the team are starting to build, and not just plan, a quantum network. UST researchers did not reply to IEEE Spectrum’s request for comments.
Tomi Engdahl says:
New, affordable detectors enable quantum communication across a bustling 20 km
How to take quantum cryptography mainstream
https://www.nature.com/articles/d42473-022-00104-2?utm_source=facebook&utm_medium=social&utm_campaign=HSCR_FOCAL_ENGM_GL_CEAP_NECGK_CF-Phot22&fbclid=IwAR1NdLbswWgDwOgUVp6fW9iJI1qTMuWJtL62Ry31PGx3AJted2YJv43lXo8
New systems promise widespread secure quantum communication by using cost-effective detectors that monitor for telltale noise in properties of optical signals sent along standard communication fibres.
Quantum computers will eventually pose a problem to standard encryption, warns Wakako Maeda, a manager in the quantum cryptography team at NEC Corporation in Tokyo, Japan. As far back as 1994, it was calculated that a quantum computer with just over 4,000 quantum bits — or qubits — could crack the security codes that keep banking details, internet transactions and communications safe from hackers, all in a matter of seconds1.
Online communication today is protected by algorithms that scramble our data, explains Maeda. The receiver is able to decode the message using a secret private key. This technique is so effective that even the world’s best supercomputers typically can’t hack these keys — without taking a period equivalent to the age of the universe to do so. But “if quantum computers, which promise to be exponentially more powerful, become common and widely used, these keys could be decrypted,” says Maeda. “This could be very disruptive to critical systems, such as those protecting national security.”
A handful of companies located in China, Switzerland and Japan, already sell small-scale quantum encryption devices, but they are prohibitively expensive. None are commercially used in Japan — however, the Japanese government is heavily investing in research and development, and has suggested it will offer tax credits to companies that introduce quantum encryption.
Since 2018, NEC, a leader in IT and network technologies, with headquarters in Tokyo, Japan, has been developing a new range of more affordable, ultra-secure quantum communication systems that partly exploit a different set of quantum features than previous cryptography systems. NEC is predicting these will be commercially available in the next few years.
In collaboration with Gakushuin University physicists, including Hirano, NEC are pioneering continuous variable quantum key distribution (or CV-QKD) systems2. These harness a less-studied, but potentially much more cost-effective, security breach detection technique.
Currently available quantum cryptographic systems all use a technique called discrete variable quantum key distribution (or DV-QKD), in which the secret key is encoded as a series of 0s and 1s in the properties of a string of single particles of light, or photons. These photons are individually detected by the receiver using photon detectors
If a hacker tries to intercept that signal, it introduces an error in the transmission of the string, explains Hirano. The method is extremely successful, but the receiving unit needs very high sensitivity, thus is expensive, says Maeda.
The NEC/Gakushuin University quantum cryptographic systems are based on CV-QKD, where, rather than monitoring the discrete clicks of incoming photons, the receiver’s detector continually measures aspects of the light’s electric field, such as its amplitude. Here “eavesdroppers are detected by an increase in excess noise” in the signal picked up by the receiver, explains Hirano. A major advantage of CV-QKD is that the detectors do not need to be as sensitive, and are much cheaper.
The optical components used in CV-QKD are found in existing commercial optical transport equipment, which reduces installation costs. In existing fibre-optic communication systems, a single optical fibre carries multiple signals simultaneously, each encoded in laser light of different wavelengths. These data signals are amplified along the way, a process that generates some noise in the fibre, but usually not enough to disrupt the signals.
Things are not so simple when a quantum signal is sent down the same line, however, because quantum signals are more sensitive to noise disruption. There is also the risk that the presence of the quantum signal would interfere with the other data travelling through the channel, causing cross-talk.
The technology can work in very noisy environments, over a range of about 20 kilometers, potentially covering a metropolitan area. “DV-QKD has been more mainstream, and more work has been done on it, so it has been somewhat surprising to be able to realize secure key distribution with CV-QKD using coherent optical communication technology,” says Maeda.
But she emphasizes that CV-QKD will not replace DV-QKD, but should be considered as a complement to it. NEC began research on DV-QKD in 1999, and DV-QKD still has certain advantages over CV-QKD. In particular, it can support a longer transmission distance of around 50 km.
NEC intends to commercialize its DV-QKD technologies in 2023, and its CV-QKD systems around 2024, she says, adding: “I think a combination of the two will be possible after that.”