Quantum networks: a major step towards the internet of tomorrow
Date:
Changed on 01/09/2025
Although the quantum internet is still at the embryonic stage, a significant leap forward has just been taken with the generic systems engineering approach developed as part of the ‘Quantum Internet Alliance’ European research programme. Acclaimed by the prestigious Nature magazine, this breakthrough relies on an secure quantum computing system developed by scientists from the QAT research team (Quantum Architectures, Algorithms, Applications and their Theory). Let’s take a closer look.
An architecture that incorporates a generic network layer
“Until now, quantum network demonstrations were conducted between laboratories via a fibre-optic link carrying photons and used solely for experimental purposes”, says Harold Ollivier, head of QAT (Computer Science Department of ENS-PSL, CNRS, Inria). “Together, we’ve crossed a threshold by building a quantum network prototype with an architecture incorporating a generic network layer, called QnodeOS.”
This system thus goes beyond the experimental laboratory environment by introducing a universal layer which is independent of the platform used, and which is already interoperable to a certain extent. This architecture is key to the programming of quantum networks. It lays the foundation for future quantum network protocols, paving the way for their widespread use across the scientific community. “The significance of this breakthrough lies in its capacity for extension”, emphasises Harold Ollivier. “Potentially, additional nodes can be integrated into the network without modifying the network layer.”
Quantum networks to connect computers
Quantum computing aims to encode and handle information directly within physical objects governed by the laws of quantum mechanics. For certain operations which cannot be carried out by standard computers, it promises unequalled computational power.
As in standard computing, researchers envision quantum computers with remote access. “We no longer imagine making calculations with our own computers installed in the basement, like in the 1950s or 60s”, laughs Harold Ollivier. “Computing resources are now held in external data centres.” Quantum computers will be no exception, especially as their performance could be enhanced when quantum tasks are shared between a network of machines.
QNodeOS architecture: this diagram, taken from the "Nature" publication (figure 2B), shows how QNodeOS, the architecture designed to run quantum network applications, is actually deployed on hardware. The CNPU (classical computer) manages the classical logic and submits the quantum tasks to the QNPU (embedded system). The QNPU interprets these quantum tasks and controls the QDevice (the quantum hardware unit). The heralding station facilitates the creation of entanglement between the qubits of the two nodes, a fundamental element for quantum network applications.
Data privacy and computing integrity, a key challenge
However, interconnecting these computers raises a challenge: how can data privacy and code integrity be guaranteed using distant quantum machines, especially in sensitive fields such as health and defence? This is where the expertise of the QAT scientists comes in. Their specialism? Studying alternative architectures to the prevailing quantum model. For example, they are studying systems using continuous variables, as opposed to discrete variables. The aim is to find practical or theoretical advantages to these alternative architectures, such as for secure computing.
Building on this expertise, QAT team members have succeeded in designing secure computing protocols that accommodate the constraints of early quantum networks. A feat revealed in the article published by Nature. “Solutions exist to protect privacy and integrity for standard computing”, remarks the QAT manager. For quantum computing, everything has to be reinvented.” Which poses a further key question: can an external quantum network provider be trusted in this respect?
Combining real and test computations
QAT has thus provided the secured computing protocols required to validate the functioning of the QnodeOS software architecture. How did they proceed? “We have developed protocols that are more flexible than those that already existed”, explains Harold Ollivier. “This enabled us to adjust to the severe constraints of quantum computing.”
Above all, the QAT members have developed an ingenious solution to make these protocols secure: give the machine a combination of real computations to be made and test computations for which the result is already known.
If the machine successfully carries out the test computations, we can only assume that it does the same for the real ones”, explains Harold Ollivier. “To make sure, the nature of the computations is actually hidden from the external provider using a technique known as ‘blinding’, which prevents them from distinguishing the real computations from the test ones. In concrete terms, we randomly change the reference system for each computation. In other words, it’s like providing navigation directions and then changing the position of the North Pole at every manoeuvre.
A European programme to develop quantum networks
According to Harold Ollivier, the Nature article is the most significant publication of the Quantum Internet Alliance European project, of which this research is a part. This project brings together 42 partners and has been allocated a budget of €25 million.
It is a good example of the coordination required in research to develop the quantum infrastructures of tomorrow”, the researcher concludes. “Nevertheless, the work must continue and public investment in quantum networks must be encouraged. The next step is to scale up, from a few qubits to millions of qubits, extending what we’ve achieved by optimising the system. Theoretically, it’s possible!
Harold Ollivier, a quantum pioneer with an unusual career path
Harold Ollivier is something of a trailblazer at Inria. He was one of the first to explore the challenges of quantum computing, back in 2001 when he was working on his thesis at the institute. He had begun in 2000, at the Los Alamos National Laboratory (United States), where he conducted research with a pioneering quantum processing team led by Wojciech Hubert Zurek, Emanuel Knill and Raymond Laflamme. It was a combination of theory and experimentation. He then did postdoctoral research at the Perimeter Institute and the Institute for Quantum Computing in Waterloo, Canada.
Halfway through his postdoctoral training, in 2006, he changed course: Harold Ollivier temporarily put research aside to join the Directorate General for Enterprise at the French Ministry of Finance, as an innovation funding officer. Two years later, he helped to create, and became head of, Institut Louis Bachelier, which applies mathematics to financial markets and encourages sustainable development in the fields of economics and finance. In 2009, he joined the risk capital investment fund, UI Investissement, before cofounding the M&A boutique Adviso Partners in 2015, then a startup called Dealsights in 2017.
He returned to research in 2019, first at CNRS, then back at Inria in 2021 where he was appointed deputy scientific director for quantum information science. At the same time, he launched and led a team devoted to quantum computing: QAT.
