Quantum communication infrastructure: Questions and answers

The aim of the QCI is to build a quantum secure communication shield across the EU that would protect our economy and society from cyber threats. The QCI’s main function will be to allow quantum key distribution (QKD), an ultra-secure form of encryption. A combination of terrestrial and space implementation of quantum-based communication infrastructure can guarantee the security of digital transactions over short and long distances covering the EU and other continents.

Early users of the QCI could be government agencies, and authorities of Member States and the EU that require a high level of security to transmit confidential information.

In the longer term, the QCI will accommodate additional functionalities alongside quantum key distribution, such as digital signatures, authentication, and secret sharing schemes like e-voting. QCI would ultimately evolve into a Quantum Internet, linking quantum processors and sensors and enabling an EU-wide distributed quantum computing and communication capability.

A technical agreement signed between the European Commission and the European Space Agency in April 2019 laid the first stone in the creation of a pan-European quantum communication infrastructure. The European Space Agency is making its expertise in satellite and optical communications available in order to meet the technological challenges of delivering quantum key distribution services, which are not achievable by ground-based solutions alone.

QKD is an extremely secure form of encryption. It uses the principles of quantum mechanics to provide the sender and recipient of an encrypted message with an intrinsically secure random key in such a way that an attacker cannot eavesdrop or control the exchange of keys.

New forms of encryption will soon be needed because public-key cryptography, which is currently widely used, will inevitably be broken by ever more powerful computing brute force, and by the advent of quantum computing itself. The race is therefore on to develop quantum-resistant cryptography and ensure the long-term security of data.

The current technologies for ground-based QKD have a distance limit due to signal light attenuation, but its range of communication can be extended by employing satellites equipped with high-quality optical links. Future concepts propose the deployment of a mixed terrestrial-satellite network. With a satellite QKD capability, cryptographic keys could be distributed to users located anywhere within the satellite’s coverage. Several cross‐linked satellites using QKD technologies could connect networks of land, sea, air, and space‐based users.

There are various options for the space-based element of the planned QKD system in the QCI. The aim is to find the optimal combination of low-earth orbit, medium-earth orbit and geostationary satellites and could even include solutions at lower altitudes. All options will have to meet user needs and requirements, and be compatible with the earth-based architecture.

The European Commission will explore these options and take into consideration technical as well as economic aspects. The Galileo, EGNOS and Copernicus programmes, as well as the proposed new GovSatcom and SST, should form the new EU space programme under the EU’s next Multiannual Financial Framework. They will be central to the EU’s future space policy. The EU space programme could play a role in this QKD system, as a user and/or enabler of the QKD-related space infrastructure.

The European Quantum Technologies Flagship was launched in October 2018, with a budget of €1 billion over the next ten years. The projects it funds aim to develop state-of-the-art devices and systems that that will be available to the QCI infrastructure. In addition, open access to the QCI will be provided to attract new stakeholders and to foster synergies with other Quantum Flagship projects.

In Europe, several countries have started to develop their own quantum communication infrastructures.

For example, a quantum network is under deployment in the Netherlands between Amsterdam, Delft, Leiden and The Hague as the first step towards a future Quantum Internet. An Italian national quantum backbone is being developed between Frejus and Matera, providing quantum time and frequency distribution alongside QKD. A fully integrated quantum/classical testbed based on novel networking paradigms ran in production sites of Telefónica Spain in central Madrid for more than three months in 2018. There are also ongoing activities in a number of other Member States including the UK, Germany, France, Poland and Austria, and Associated Countries like Switzerland.

Several regions around the world have begun to build quantum communication infrastructures in various ways, deploying several small-scale fibre networks with different architectures and also demonstrating key distribution from Low Earth Orbit satellites. China is currently the undisputed leader in the field, having deployed a continental-scale quantum backbone based on trusted nodes, several metropolitan access networks with hundreds of access points, and a research satellite named Micius. Quantum networks are also being deployed in South Korea, Japan, and in the USA.

Quantum computing involves the use quantum-mechanical phenomena, such as superposition and entanglement, to perform computational tasks. Quantum-mechanical phenomena involves the interactions of molecules, atoms, and even smaller particles like photons and electrons.

Quantum computing is radically different from classical computing, which is based on binary bits that can be either zero or one. A quantum bit, or qubit, can be 'simultaneously' in zero and one, and this feature of quantum physics, called superposition, can be used to perform parallel computation. This means quantum computers can exploit the superposition of many zeros and ones to compute them at the same time instead of one at a time, and so work much faster than classical computers.

While universal (general purpose) quantum computers are still far away, some simple devices are starting to be built. By 2021, the EU will have its first prototype quantum computers, funded by the Quantum Flagship. The new Digital Europe programme aims to provide the EU with its first quantum computing infrastructure open to scientists and engineers, from academia and industry, by the end of the next Multi-annual Financial Framework period 2021–2027.

The Quantum Internet does not yet exist, but it is the long-term (15-20 year) objective of the EU’s strategy on quantum technologies. It will work by interconnecting quantum computers, simulators and sensors via quantum networks that distribute information and quantum resources.