In the digital age, the internet has transformed the world. Now, a new era dawns as researchers push the boundaries, aiming to materialize the vision of a quantum internet. This innovative network promises to revolutionize communication by enabling quantum-based interactions across vast distances. The potential is immense, and the vision of a quantum internet is to build a universal quantum network that can be programmed to run any type of future quantum network application. Building on the principles of quantum mechanics, such as entanglement, this quantum internet is not just theoretical speculation—it’s rapidly transitioning from concept to practical reality.
Quantum Internet: Where Classical Meets Quantum
Just as the classical internet relies on bits, the quantum internet is anchored in qubits. Quantum bits transcend the binary limitations of classical bits, existing simultaneously as both 0 and 1 through a phenomenon known as superposition. Additionally, qubits can be entangled, causing them to exhibit coordinated behaviors, even when separated by substantial 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.
Advantages of Entanglement: Security and Coordination
Entanglement forms the cornerstone of quantum communication. Its unique characteristics offer heightened coordination and impervious security. Beyond enhancing coordination between distant points, entanglement ensures communication security by making qubits uncopyable and detecting any attempt at duplication. This inherent privacy feature makes entanglement ideally suited for applications requiring top-notch security and confidentiality.
Quantum Key Cryptography and Ongoing Challenges
Quantum Key Cryptography (QKD) capitalizes on these properties, using single photons to enhance the security of communication systems and data networks. However, deploying QKD over extended distances poses challenges due to transmission losses. Current quantum communication links are primarily direct, point-to-point connections limited to about 300-500 km due to losses in the fiber. The inability to amplify quantum signals in the same manner as electronic signals is a critical hurdle.
A Blueprint for the Global Quantum Network
To realize a global quantum network, existing optical networks must be harnessed. The transition from point-to-point links to quantum networks necessitates the development of quantum repeaters to manage photon losses in optical fibers and routers to switch signals. Constructing and scaling quantum networks require a synchronized effort across physics, computer science, and engineering.
Prototypes, Initiatives, and Milestones
Remarkable progress has been achieved on this journey. Metropolitan Quantum Key Distribution (QKD) networks are operational, providing the blueprint for larger-scale implementations. In China, basic quantum networks have been established, though the standardization of commercial quantum repeaters remains a challenge. Initiatives like the Quantum Internet Alliance are driving the endeavor forward.
In China, extensive quantum networks have already been built using 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.
Developing the quantum network also relies on the use of quantum satellites 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.
The Quantum Leap: United States’ Initiative
The United States is poised to accelerate quantum internet development through the “Quantum Leap” initiative led by the National Science Foundation (NSF). This strategic endeavor envisions a national quantum internet driven by a collaboration of agencies, laboratories, and academic institutions. Key milestones have already been achieved, including long-distance quantum networks and photon entanglement across significant spans.
The United States is planning to build a nationwide quantum internet, a network that would use quantum mechanics to transmit information securely and at speeds that are far faster than traditional networks.
The development of a nationwide quantum internet is still in its early stages, but there have been some recent progress. In February 2020, the U.S. Department of Energy (DOE) released a blueprint for the development of a national quantum internet. The blueprint outlines the key research and development challenges that need to be addressed in order to build a nationwide quantum internet, and it sets out a roadmap for achieving this goal.
Since the release of the blueprint, there have been a number of projects underway to develop the technology needed for a nationwide quantum internet. In 2021, for example, researchers from the National Institute of Standards and Technology (NIST) and the University of Chicago successfully entangled photons over a distance of 100 kilometers. This is a significant milestone, as it is the longest distance that photons have been entangled to date.
Other projects are underway to develop quantum repeaters, which are devices that can amplify quantum signals over long distances. Quantum repeaters are essential for building a nationwide quantum internet, as they will allow quantum signals to be transmitted over long distances without losing their quantum properties.
The development of a nationwide quantum internet is a complex and challenging undertaking, but it is one that has the potential to revolutionize the way we communicate and share information. If successful, a nationwide quantum internet could be used to secure financial transactions, develop new medical treatments, and create new forms of artificial intelligence.
Here are some of the latest developments on the US plan to build a nationwide quantum internet:
- In July 2022, the DOE announced that it would be investing $1 billion over five years to support the development of a nationwide quantum internet.
- In September 2022, the National Science Foundation (NSF) announced that it would be awarding $100 million in grants to support quantum networking research.
- In October 2022, the European Union announced that it would be investing $1 billion over five years to support the development of a pan-European quantum internet.
These investments are a sign of the growing interest in quantum internet technology around the world. With continued investment and research, it is likely that a nationwide quantum internet will become a reality in the coming years.
The Quantum Future: A World Transformed
The impact of a fully realized quantum internet is profound. Industries spanning from banking to health services, and national security communication stand to be revolutionized. Quantum networking promises exponential enhancements in data transmission, sensing networks, quantum computing, and image processing.
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. While running their computations, they might want to transmit quantum-encrypted information between their personal computer and the cloud-based quantum computer.
Applications Beyond Imagination
It’s not just an evolution of the current internet; it’s an amalgamation of classical and quantum networks unlocking a realm of unprecedented possibilities.
While the full spectrum of quantum internet applications remains speculative, some significant uses have emerged. These include secure communication, global atomic clock synchronization, supercharged telescopes, and quantum-enhanced detection of phenomena like 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.
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.
Quantum networking, working in tandem with the classical internet, is poised to achieve feats unattainable through classical information processing alone.
The Quantum Odyssey: Stages of Development
The journey to a quantum internet is multifaceted, involving six stages of development. From basic networks supporting secure communication to intricate networks of fully-connected quantum computers, each stage offers increased functionality and progressively advanced applications.
SIX STEPS TO A 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. Researchers have laid out six stages of sophistication that a future quantum internet could reach, and what users could do at each level.
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’.
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.
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.
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.
Conclusion: A Quantum World Awaits
The pursuit of a quantum internet has transcended theory to become a realm of tangible innovation. Through dedicated research, interdisciplinary collaboration, and unwavering technological advancements, the quantum internet stands on the precipice of reshaping our connected world. While achieving a global quantum internet may not be an overnight process, the strides made underscore a future where science fiction becomes a reality, and the potent capabilities of quantum mechanics transform the very fabric of connectivity as we know it.
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