Future benefits of the quantum internet

This classical information theory is based on the principle of ‘or’ logic. A statement is either true or false. A tossed coin lands on heads or tails. In a card game, if your hand does not include the king of hearts, then you know it is held by opponent 1, opponent 2 or opponent 3. We explore every possibility using ‘or’ logic. 

But quantum physics undermines this understanding of the world. “One of the difficulties here lies in the fact that reasoning with ‘or’ logic is not possible with an unknown element of information.” Thomas Young’s interference experiment illustrates this concept perfectly. It consisted in sending a particle from a light source towards a plate pierced with two holes. According to the rules of classical physics, the particle must pass through hole 1 or hole 2, regardless of the method by which it is emitted. But in quantum physics, the light particle can be emitted in such a way as to contradict the “hole 1 or hole 2” theory. The particle does indeed pass through both holes! We say that it passes through hole 1 and hole 2 in a state of quantum superposition.  It is precisely this questioning of ‘or’ logic that forms the basis of quantum supremacy, when quantum computing performs better than classical computing. This concept thus applies to situations in which quantum superposition enables a quantum computer to perform calculations faster than a classical supercomputer. A topic at the core of Marc-Olivier Renou's research.

The history of quantum supremacy

Quantum supremacy is not a new concept. Its origins lie in a thought experiment conducted by Albert Einstein, Boris Podolsky and Nathan Rosen, known as the EPR paradox, which inspired Erwin Schrödinger for his famous cat experiment involving the quantum superposition of two states of a cat, alive and dead. Even in 1935, the four physicists identified the problem with ‘or’ logic in quantum physics, considering it to be a flaw in the theory. Albert Einstein is said to have described it as a “ghostly remote effect”, and Erwin Schrodinger allegedly stated that it led to “patently absurd” situations. They therefore concluded that quantum physics was incomplete.

In 1964, John Stewart Bell demonstrated that no theory capable of explaining quantum physics was compatible with the principle of ‘or’ logic, by using quantum entanglement, a phenomenon by which two systems, even separated by a large distance, share a state of quantum superposition. More specifically, he showed that correlations observed between measurements of these particles were incompatible with ‘or’ logic.  John Bell thus laid the foundations of quantum supremacy theory. 

These links between systems, addressed by Bell’s theorem, were later applied in 1976 by John Clauser, then in 1982 by Alain Aspect, whose experiments provided very convincing evidence that the quantum entanglement phenomenon was necessary in explaining the reality of the physical world. For this demonstration, they both received the Nobel Prize in 2022. In 2015, an experiment conducted by Ronald Hanson from Delft University in the Netherlands confirmed once and for all the reality of quantum entanglement, removing any remaining doubt about the limits of early 1980s technology in previous experiments. 

Opening up new possibilities with quantum computing in distributed systems

The PhIQuS team is conducting research in this area to gain a better understanding of quantum information. “Being freed from the bonds of ‘or’ logic opens up an extraordinary potential”, enthuses Marc-Olivier Renou. “The fact that units of quantum information – or qubits – can coexist in different states makes it possible to efficiently solve problems that are complex, difficult, or even impossible for classical computer science to unravel.” Peter Shor’s algorithm is the most famous example of the benefits of quantum processing. In theory, quantum computers are capable of finding the prime factors of an integer much faster than any classical computer. 

The originality of PhIQuS lies in its choice to study quantum supremacy in distributed systems, when information is shared between computers located in different rooms or different cities, which might even be Saclay and Tokyo or elsewhere in the world, each addressing a different part of the problem. 

In other words, superposition allows us to study simultaneously many different states of each qubit, while entanglement creates unique correlations between different qubits. This is what makes it possible to outperform classical information technology. 

PhIQuS project team: exploring quantum information 

Officially launched in 2025, the PhIQuS team (physics, information theory and quantum simulation) is one component of an entire quantum ecoystem located on the Saclay plateau. It is thus the third team from the Inria Saclay centre to work on this topic, after Quriosity and Quacs. The work of PhIQuS began in 2023 with the recruitment of its manager, Marc-Olivier Renou. The team’s combined expertise, from the École Polytechnique, CNRS and Inria, with Marc-Olivier Renou, Filippo Vicentini, a physicist at CPHT and Titouan Carette, a computer scientist from LIX at the École Polytechnique, is being used to explore the theoretical basics of quantum information. In addition, the mathematician Igor Klep (see below) has joined the team as a guest professor, along with around fifteen PhD students and post-doctoral researchers.

The PhIQuS team’s work focuses on three areas:

• Information theory, which studies the fundamental differences between classical and quantum information, especially in distributed computer science.
• Condensed matter physics, to understand the collective phenomena arising when very large numbers of particles interact, with the help of machine-learning-based methods, such as neural quantum states. The aim is to find out what makes a material superconductive, or how to produce a battery capable of storing more energy...
• Formalisation and representation for quantum computing, to develop abstract representations for the conceptualisation of and reasoning on quantum calculations and objects, based on mathematical category theory.

The newly-created team has already achieved national and international recognition and receives funding, including two grants through the ANR Young Researcher programme, a Marie Curie grant allocated to its post-doctoral researcher,  Lucas Tendick, and financial support from the QuantERA project, following a European call for proposals. PhIQuS also has a special partnership with Nokia Bell Labs, who are currently funding two CIFRE theses for the team.

PhIQuS already producing results

The question of quantum supremacy is therefore relevant in distributed systems. The aim is to achieve overall consistency in order to find fast and reliable solutions to problems using the fewest possible resources. “The notion of supremacy in distributed quantum computing has barely been explored. This work is carried out by physicists who are quantum experts but do not fully understand network technology, or by computer scientists who know all about networks but have little knowledge of quantum physics”, Marc-Olivier Renou points out. “Butthe PhIQuS team unites both fields of expertise.”  

Although formed only recently, the team has already published three articles for STOC, the theory of computation conference, in 2024 and 2025. 

"Network management (for example, the allocation of frequencies to allow a large number of mobile phones to communicate with antennas) is directly related to these questions. By fully understanding which problems can potentially be solved more quickly with the help of quantum computing, we can develop accordingly the quantum networks of tomorrow.”  

Beyond this very fundamental research, the PhIQuS team are considering experimental implementations of their theoretical progress, by joining forces with other scientists working in more applied fields. Watch this space...

Find out more 

• International research collaboration on quantum physics with visiting professor igor klep, Institut Polytechnique de Paris, 23/6/2025.
• Quantum-Saclay: bringing quantum together, Institut Polytechnique de Paris, 30/4/2025.
• Où se cache l’avantage quantique ? Pour la Science, 15/4/2024.
• Où en est la révolution quantique ? CNRS, 25/1/2024.
• La non-localité quantique à l’ère des réseaux, Pour la Science, 20/9/2021.

Experts 

• Distributed quantum advantage for local problems, Proceedings of the 57th Annual ACM Symposium on Theory of Computing (STOC), 15/6/2025.
• Online locality meets distributed quantum computing, Proceedings of the 57th Annual ACM Symposium on Theory of Computing (STOC), 15/6/2025.
• No distributed quantum advantage for approximate graph coloring, Proceedings of the 56th Annual ACM Symposium on Theory of Computing (STOC), 11/6/2024.