Quantum internet on the cusp of the internet revolution

Europe’s Quantum Internet Alliance is working on the development of networks which can provide many benefits, including impenetrable end to end communication.

The Quantum Internet Alliance (QIA) forms part of the EU’s Quantum Technologies Flagship, at the cutting edge of quantum network exploration. The QIA aims to create the foundations of a quantum internet that can be rolled out internationally through the creation of quantum systems and infrastructure.

The birth of quantum mechanics has brought us atomic clocks, GPS, laser and precision technology; and telecommunications. Now, a new wave of quantum advancements is upon us, providing the opportunity for new technologies. In 1981 Feynman sparked the advent of quantum computing, followed by the Shor algorithm in 1991 that allows quantum computers to break classic encryption mechanisms. Since then, people across the world have been working on quantum networks.

Encompassing all the advanced networking in the EU flagship, the project is tailored to the main target of future quantum networks. With an aim to increase the distance that quantum information can be sent over and to increase functionality so that potential network applications that the quantum internet can offer can be run. This involves an effort in the domain of hardware – making quantum devices – as well as software. We spoke to Stephanie Wehner, project co-ordinator at QIA, QuTech, Delft University of Technology, about the project and what implications quantum internet can have for security and communication.

How is the quantum internet different from the internet we use today? What does quantum communication infrastructure consist of?

The internet we use now works by transmitting classical information – this means ‘bits’ – a series of zeroes and ones that we can print on a piece of paper. Any kind of information that is classical can be printed on a piece of paper and sent around. Over a quantum internet we send quantum bits (qubits) which have quantum superposition, they can be a zero and one at the same time. Like Schrödinger’s cat it can be dead and alive – classically the cat is either alive or dead but with qubits it can be dead and alive at the same time.

The form of the quantum internet infrastructure consists of quantum devices, which are attached to such a network so they can send and receive qubits. These can be simple photonic devices that can only prepare a qubit and send it somewhere or receive a qubit and measure it. It can also be more complicated with devices such as small quantum computers.

The second part of the quantum communication infrastructure is communication channels – classical bits can be sent over many telecom fibres. These are the same fibres that are used for quantum communication. In this project we do something that is quite sophisticated. We are going to demonstrate a proof of principle of what is called ‘Secure quantum computing in the cloud’, which is more complicated than secure communication.

How does quantum key distribution rival current encryption methods and how will it be able to provide security against quantum computers in the future?

To use this for secure information we can use quantum key distribution (QKD). With this you can make a new encryption key which is shared between the sender and the receiver – or many of them – and which are then used in conventional encryption based on one-time pad encryption, which cannot be broken since the key is as long as the message. Qubits have a fundamental property that they cannot be copied – this is really a fundamental thing in nature, so it is something that nature forbids you to do, it is impossible. You can prove mathematically that according to the laws of quantum mechanics it is impossible for anyone to learn the key if we use quantum communication. With classical information protocols you can make hundreds of copies on a piece of paper, for example – and also no one will ever know I have done this – but this is very different in the quantum internet world. If you try to copy a qubit such an attempt can be detected. This is one of the reasons qubits are so good at security sensitive applications. It is detected by the fact that if you try and make a copy you partially measure a qubit you destroy the superposition between zero and one.

This is very different from conventional methods. More conventional methods ensure secure communication by relying on some assumptions, for example, that you cannot easily determine the prime factors of a large number. Importantly, QKD does not rely on such assumptions.

With current methods of encryption there is always the risk that someone records what you are communicating and can buy a quantum computer in five or ten years that they can use that to break the encryption you are using today. Quantum computers can be used to break conventional cryptosystems; however, they will not be able to break the security of QKD.

What sort of infrastructure can the quantum internet provide security for and how?

In principle quantum communication can deliver security for any kind of data transmission. The most interesting thing is to use it for highly secure, security sensitive applications. This includes the security of highly critical infrastructure such as power grids and water management systems. For these systems it is critical to have a secure aspect.

Secondly, it can be used to secure financial transactions. We currently have a project with a Dutch bank, ABN Amro, where quantum communication will be used to secure banking transactions. It is important to understand with quantum communication we can also do things that are not QKD. We can use it for clock synchronisation or to perform secure computation on future quantum computers in the cloud so there are many applications.

Another example is quantum simulation. What this means is, say for example you have designed a new material or medicine and you want to explore its chemical properties. One way you can do this is to make the material in the lab and experiment to find out what is going on. However, with a quantum computer one can efficiently simulate quantum chemistry in order to explore a design for a new material. In the future, maybe not everyone will have one of these quantum computers and if you want to explore something, you might not want to send it off to someone with a quantum computer as they will find out the material design. What you can do it use the quantum computer in such a way that it cannot learn what your material design is – this is possible with a quantum internet system – the net allows you to connect to the quantum computer in such a way that it cannot find out what you are using it for.

What progress has been made on the controlling and manipulation of quantum signals? How long can quantum information be stored for and what is the furthest distance and fastest time over which we are able to send the information?

This is a complex question – I would say that a lot of progress has been made but there is no ‘quantum repeater’ yet which will allow us to send quantum signals over long distances through fibre. In our flagship programme, we want to demonstrate a key aspect in making that happen. The reason it is difficult is the special feature of the qubits – they cannot be copied, which is good for security. However, this is not always advantageous, as if it gets lost, we cannot retrieve the information; it is gone forever.

It depends at the moment in regard to how far we can send the information. You can send information over commercial fibre on the ground roughly 100km, up to 400km but this is in the lab on extremely high quality fibres and network nodes which are physically close. Qubits have also been sent from space over very large distances of 1,200 km, but in a very slow way. If you were to calculate how long it would take you to make an encryption key with that satellite, it would take you more than 300 days. The Chinese satellite was overhead in the sky for 275 seconds a day and could make entanglement at the rate of one hertz, so one cycle per second. This is very slow as you need to wait many days. The biggest challenge in quantum communication is to go faster.

To increase the speed there are many things you can do. For example, the system we have here at Delft University has a native wavelength of 640 nanometres; and that is not in the telecom wavelength. Telecom is roughly 1,550 nanometres, and that makes a big difference because the losses are much smaller at telecom wavelength. This means we can go much faster because we convert to the telecom wavelength – meaning fewer photons are lost on the fibre.

The system that we have at the Quantum Internet Alliance can be connected to a network on a tiny quantum computer, where we can store qubits for roughly two seconds. This does not seem a lot, but it is huge by international standards. The longer we can store it, the larger the systems you can hope to send quantum information over. If you want to send information over longer distances you can use an intermediate station but then you want to store the qubits at this location for a small amount of time and this depends on how long the chain of nodes is – the longer the distance the longer the information needs to be stored for.

What are the main theoretical challenges for this project and how long do you think it will be until quantum internet can be rolled out internationally?

From the physics perspective, the main theoretical challenge is that we don’t actually know yet how to make a large scale quantum network. There are currently several different systems, and no one knows which one is best yet, as we don’t know the systems’ scaling behaviour. One of the main outcomes of this project is to design for a pan-European quantum network architecture which we want to validate in simulation. We have a purpose-built simulation platform for quantum networks and use certain theoretical tricks which enable us to perform large scale network simulation.

A good element of quantum communication is that we can already communicate at short distances – people can currently buy commercial devices that do point to point QKD if the distance is not more than 100km. This means that the path between what we can do now and a full-blown quantum internet of the future is a very gradual one. We want to do longer distances and increase functionality. Our project goes beyond that because we connect quantum processors in different cities, and this forms the first basis of doing quantum communication over long distances.

If quantum computing is becoming more important for security, how can Europe ensure that brain drain does not happen and retain its knowledge base for security purposes?

I think it is very important to provide strong, focused and strategic funding in Europe – there should be more money in quantum technology. However, throwing more money at it is not enough – we need to think about how the money is used. Adopting a focused and very engineer-orientated and driven strategy will have the most impact. The time when a single researcher can go into the lab and make progress has passed. Internationally we are currently world leading in advanced quantum networking on the ground, but significant effort is needed to stay ahead in the international competition.

Quantum computing can deliver unprecedented security but also has many other beneficial applications and more will be discovered in the future. In the 1970s people did not know what the internet would be good for, so we are in a similar situation now.

I think it is very important that many people have access to this technology at an early stage to perform development themselves. One would imagine you could create an innovation hub where early networks are available, and people can use this network to develop software to integrate and develop security policies. There is a big gap between what we do and the end user that cannot be bridged very easily – you need an entire ecosystem based around these networks, with fibre providers, service providers, security professionals and software that can be integrated into existing infrastructure; and totally new applications we have not thought about yet. It is important that there is an innovation hub in Europe that is open where anyone can come and develop a new piece of software on the network and use it as a springboard to develop more technology.

Stephanie Wehner

Project Co-Ordinator

Delft University of Technology

Quantum Internet Alliance


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