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The internet has had a revolutionary impact on our world. Now researchers are moving towards the vision of a quantum internet that will provide fundamentally new internet technology by enabling quantum communication between any two points on Earth by exploiting phenomena from quantum physics, such as entanglement.
While classical internet was based on digital bits that can take only two values, 0 or 1, the Quantum internet will transmit qubits that can be in a superposition of being 0 and 1 at the same time. Moreover, qubits can be entangled with each other, leading to strong correlations over large distances. This makes them act in seemingly coordinated ways (such as spinning in opposite directions) even when they are separated by vast distances.
This property of entanglement allows improved coordination between distant sites. This makes it extremely suitable for tasks such as clock synchronization or the linking of distant telescopes to obtain better images. The second is that entanglement is inherently secure. If two quantum bits are maximally entangled, then nothing else in the universe can have any share in that entanglement. Qubits also cannot be copied, and any attempt to do so can be detected. This feature makes entanglement uniquely suitable for applications that require security and privacy.
Researchers have developed Quantum encryption, called Quantum Key Cryptography (QKD) using single photons for boosting the security of communication systems and data networks. However, there are challenges in applying the method over large distances due to transmission losses. Currently Most Quantum Communication links are direct point-to-point links through telecom optical fibers and, ultimately limited to about 300-500 km due to losses in the fiber. The quantum signals can’t be amplified like an electronic signal, either.
To realize it in a global scale for arbitrary users, it is reasonable to utilise also existing optical networks that have already been installed in the world. To develop these points to point links into quantum networks and future global internet requires quantum repeaters for taking care of photon loss of optical fibres and routers for switching the signals.
Building and scaling quantum networks is a formidable endeavor, requiring sustained and concerted efforts in physics, computer science, and engineering to succeed. Toward its practical realization, tremendous progress has been made during the past decades. Metropolitan QKD networks have been successfully deployed and is going to be a continental scale.
In China, extensive quantum networks have already been built use simple “trusted nodes” that measure and retransmit information about quantum states. But quantum repeaters at the present time are a long way from becoming standardized commercial products.
A team at Delft has already started to build the first genuine quantum network, which will link four cities in the Netherlands. The project, set to be finished in 2020, could be the quantum version of ARPANET, a communications network developed by the US military in the late 1960s that paved the way for today’s Internet.
Wehner, who is involved in the effort, is also coordinating a larger European project, called the Quantum Internet Alliance, which aims to expand the Dutch experiment to a continental scale. As part of that process, she and others are trying to bring computer scientists, engineers and network-security experts together to help design the future quantum internet.
Developing the quantum network also relies on the use of quantum satellite which can connect over large distances, China has already launched a quantum satellite. Jian-Wei Pan of the University of Science and Technology of China, who leads the research on the satellite, has said that he wants to launch more quantum satellites in the next five years. By 2030, he’s hoping that quantum communications will span multiple countries. In 13 years, you can expect quantum internet.
https://www.youtube.com/watch?v=406H9W583Uw
Huge imminent investments in quantum technologies will bring concepts like a global quantum Internet and quantum Internet-of-Things, closer to reality. United States with the new NSF ‘Quantum Leap’ initiative, in Europe and in China, the idea of a quantum Internet is gaining significant traction.
US is planning a nationwide quantum internet
The U.S. Department of Energy (DOE) has presented a report outlining a strategy for the development of a national quantum internet, with the aim of “bringing the United States to the forefront of the global quantum race and ushering in a new era of communications.” The DOE’s 17 National Laboratories will serve as the backbone of the coming quantum internet, which will transmit information more securely than ever before, stated the DOE. “Currently in its initial stages of development, the quantum internet could become a secure communications network and have a profound impact on areas critical to science, industry, and national security,” said the launch statement.
Crucial steps toward building such an internet are already underway in the Chicago region, which has become one of the leading global hubs for quantum research. In February, 2020, scientists from DOE’s Argonne National Laboratory in Lemont, Illinois, and the University of Chicago entangled photons across a 52-mile “quantum loop” in the Chicago suburbs, successfully establishing one of the longest land-based quantum networks in the nation. That network will soon be connected to DOE’s Fermilab in Batavia, Illinois, establishing a three-node, 80-mile testbed.
“The combined intellectual and technological leadership of the University of Chicago, Argonne, and Fermilab has given Chicago a central role in the global competition to develop quantum information technologies,” said Robert J. Zimmer, president of the University of Chicago. “This work entails defining and building entirely new fields of study, and with them, new frontiers for technological applications that can improve the quality of life for many around the world and support the long-term competitiveness of our city, state, and nation
Once developed, quantum networking will be used in banking, health services, aircraft communications, and other applications for national security before gradually rolling it out for use in mobile phones. Scientists are working on how to use it better during the transmission of huge amount of data. Other potential areas where quantum technology can be deployed include image processing, searching for oil, gas and mineral deposits, and also earthquake prediction using ultra-sensitive quantum sensors.
Creating a full-fledged prototype of a quantum internet will require intense coordination among U.S. Federal agencies—including DOE, the National Science Foundation, the Department of Defense, the National Institute for Standards and Technology, the National Security Agency, and NASA—along with National Laboratories, academic institutions, and industry. The DOE report lays out crucial research objectives, including building and then integrating quantum networking devices, perpetuating and routing quantum information, and correcting errors. Then, to put the nationwide network into place, there are four key milestones: verify secure quantum protocols over existing fiber networks, send entangled information across campuses or cities, expand the networks between cities, and finally expand between states, using quantum “repeaters” to amplify signals.
“The foundation of quantum networks rests on our ability to precisely synthesize and manipulate matter at the atomic scale, including the control of single photons,” commented David Awschalom, Liew Family Professor in Molecular Engineering at the University of Chicago’s Pritzker School of Molecular Engineering, senior scientist at Argonne National Laboratory, and director of the Chicago Quantum Exchange. “Our National Laboratories house world-class facilities to image materials with subatomic resolution and state-of-the-art supercomputers to model their behavior. These powerful resources are critical to accelerating progress in quantum information science and engineering, and to leading this rapidly evolving field in collaboration with academic and corporate partners.”
Quantum Internet Applications
As with any radically new technology, it is hard to predict all uses of the future quantum internet. However, several major applications have already been identified, including secure communication, synchronisation of atomic clocks among arbitrary clients all over the globe, and building ultra-sharp telescopes using widely separated observatories and even establishing new ways of detecting gravitational waves. It will also provide secure identification, achieving efficient agreement on distributed data, exponential savings in communication, quantum sensor networks, possibly even simulation of quantum many-body systems as well as secure access to remote quantum computers in the cloud.
Such a quantum internet will—in synergy with the “classical” internet that we have today—connect quantum information processors in order to achieve unparalleled capabilities that are provably impossible by using only classical information.
The early adopters of the highest-stage networks will probably be scientists themselves. Labs will get to connect to the first advanced quantum computers remotely, or to link up such machines to work as a single computer.
They could then use these systems to perform experiments that aren’t possible with classical machines, for example, simulating the quantum physics of molecules or materials. Networks of quantum clocks could dramatically increase the precision of measurements for phenomena such as gravitational waves, and distant optical telescopes could link up their qubits to sharpen images.
The quantum internet could also be useful for potential quantum computing schemes, says Fu. Companies like Google and IBM are developing quantum computers to execute specific algorithms faster than any existing computer. Instead of selling people personal quantum computers, they’ve proposed putting their quantum computer in the cloud, where users would log into the quantum computer via the internet. While running their computations, they might want to transmit quantum-encrypted information between their personal computer and the cloud-based quantum computer. “Users might not want to send their information classically, where it could be eavesdropped,” Fu says.
In the near future, the quantum internet could be a specialized branch of the regular internet. Research groups all over the world are currently developing chips that might allow a classical computer to connect to a quantum network. People would use classical computing most of the time and hook up to the quantum network only for specific tasks. For example, says physicist Renato Renner of ETH Zurich, you might connect a classical personal computer to a quantum network to send a message using quantum cryptography—arguably the most mature quantum technology.
Some see it as one day displacing the Internet in its current form. “I’m personally of the opinion that in the future, most — if not all — communications will be quantum,” says physicist Anton Zeilinger at the University of Vienna, who led one of the first experiments on quantum teleportation1, in 1997.
Six Stages for Quantum Internet
A prominent team of quantum-internet researchers at Delft University of Technology in the Netherlands has now released a roadmap laying out the stages of network sophistication — and detailing the technological challenges that each tier would involve. Their predictions are described in Science1 on 18 October.
It describes six phases, starting with simple networks of qubits that could already enable secure quantum communications – a phase that could be reality in the near future. The development ends with networks of fully quantum-connected quantum computers. In each phase, new applications become available such as extremely accurate clock synchronization or integrating different telescopes on Earth in one virtual ‘supertelescope’. This work creates a common language that unites the highly interdisciplinary field of quantum networking towards achieving the dream of a world-wide quantum internet.
The lowest stage of a true quantum network – a prepare and measure network – allows the end-to-end delivery of quantum bits between any two network nodes, one quantum bit at a time. This is already sufficient to support many cryptographic applications of a quantum network. The highest stage is the long-term goal of connecting large quantum computers on which arbitrary quantum applications can be executed.
SIX STEPS TO A QUANTUM INTERNET
Researchers have laid out six stages of sophistication that a future quantum internet could reach, and what users could do at each level.
0 Trusted-node network: Users can receive quantum-generated codes but cannot send or receive quantum states. Any two end users can share an encryption key (but the service provider will know it, too).
The first — which they say is a sort of stage 0 because it does not describe a true quantum internet — is a network that enables users to establish a common encryption key, so that they can share their (classical) data securely. The quantum physics occurs only behind the scenes: the service provider uses it to create the key. But the provider also knows the key, which means that users have to trust it. This type of network already exists, most notably in China, where it extends over some 2,000 kilometres and connects major cities including Beijing and Shanghai.
1 Prepare and measure: End users receive and measure quantum states (but the quantum phenomenon of entanglement is not necessarily involved). Two end users can share a private key only they know. Also, users can have their password verified without revealing it.
In stage 1, users will start getting into the quantum game, in which a sender creates quantum states, typically for photons. These would be sent to a receiver, either along an optical fibre or through a laser pulse beamed across open space. At this stage, any two users will be able to create a private encryption key that only they know.
The technology will also enable users to submit a quantum password, for example, to a machine such as an ATM. The machine will be able to verify the password without knowing what it is or being able to steal it.
Stage 1 has not been tried on a large scale, but it is already technologically feasible at the scale of small cities, Wehner says, although it would be very slow. A group led by Pan Jian-Wei at the University of Science and Technology of China in Hefei made the world record for this kind of transmission in 2017, when they used a satellite to link two laboratories more than 1,200 kilometres apart.
2 Entanglement distribution networks: Any two end users can obtain entangled states (but not to store them). These provide the strongest quantum encryption possible.
In stage 2, the quantum internet will harness the powerful phenomenon of entanglement. Its first goal will be to make quantum encryption essentially unbreakable. Most of the techniques that this stage requires already exist, at least as rudimentary lab demonstrations.
3 Quantum memory networks: Any two end users to obtain and store entangled qubits (the quantum unit of information), and can teleport quantum information to each other. The networks enable cloud quantum computing.
4 & 5 Quantum computing networks: The devices on the network are full-fledged quantum computers (able to do error correction on data transfers). These stages would enable various degrees of distributed quantum computing and quantum sensors, with applications to science experiments.
Stages 3 to 5 will, for the first time, enable any two users to store and exchange quantum bits, or qubits. These are units of quantum information, similar to classical 1s and 0s, but they can be in a superposition of both 1 and 0 simultaneously. Qubits are also the basis for quantum computation. (A number of laboratories — both in academia and at large corporations, such as IBM or Google — have been building increasingly complex quantum computers; the most advanced ones have memories that can hold a few dozen qubits.)
Getting to the final stage will require several breakthroughs. Hanson’s team has been at the forefront of these efforts and is among those working to build the first ‘quantum repeater’ — a device that can help to entangle qubits over larger and larger distances.
More advanced stages are distinguished by a larger amount of functionality, thus supporting ever more sophisticated application protocols. In parallel to the daunting experimental challenges in making quantum internet a reality, there is thus an opportunity for quantum software developers to design protocols that can realize a task in a stage that can be implemented more easily.
The proposed stages of development will facilitate interdisciplinary communication by summarizing what we may actually want to achieve and providing guidelines both to protocol design and software development as well as hardware implementations through experimental physics and engineering.
In addition to providing a guide to further development, the work sets challenges both to engineering efforts and to the development of applications. Many other applications of a quantum internet are already known, and more are likely to be discovered as the first networks come online.
“On the one hand, we would like to build ever more advanced stages of such at network”, says Stephanie Wehner, lead author of the work, “On the other hand, quantum software developers are challenged to reduce the requirements of application protocols so they can be realized already with the more modest technological capabilities of a lower stage.”
Although it is hard to predict what the exact components of a future quantum internet will be, it is likely that we will see the birth of the first multinode quantum networks in the next few years.
But it’ll take a while—if ever—before a quantum network gets as big or as versatile as our current internet. “To get to the point where billions of quantum devices are connected to the same network, where any connected device can talk to any other device, we’d be lucky to see it in our lifetime,” Jennewein says.
References and resources also include:
https://optics.org/news/11/7/49
