Paris-Saclay teams carry out research work at the highest international level and cover a very large part of quantum science and technology. They focus on the most fundamental and theoretical studies as well as on experimental and technological developments. They explore many possibilities for the development of quantum functionalities, ranging from particles without mass or interaction such as photons, single isolated atoms and interacting atoms to mesoscopic electronic systems based on semiconductors or superconductors. They rely on complex experimental developments in optics, as well as on tools for the creation and characterisation of condensed matter and on nanotechnologies.
This research work is perfectly in line with the European Flagship on Quantum Technologies: quantum computation, quantum communications, quantum simulation and quantum sensors. It benefits from pioneering fundamental studies, particularly in the areas of quantum matter and technological research.
Major research topics
- Quantum communications and post-quantum cryptography
- Quantum sensing and metrology
- Quantum photonics
- Quantum electrical circuits
- Quantum simulation
- Quantum and topological materials
- Quantum algorithms
Quantum communications and post-quantum cryptography
The fundamental laws of quantum mechanics have made it possible to imagine communication protocols with the guarantee of absolute security. They could first be applied through the exchange of quantum cryptographic keys: the work of Paris-Saclay was pioneering in this area and the systems are almost ready for technological transfer. Moreover, the security of the current communications, which use the RSA encryption system, is threatened by the ongoing development of quantum computers. Another challenge is to imagine conventional encryption protocols which would resist the decoding abilities of a quantum computer: this corresponds to the field of post-quantum cryptography.
To learn more:
- Physical review letters 89 (18), 187901 (2002)
- Nature volume 421, pages238–241 (2003)
- Nature Photonics volume 7, pages 378–381 (2013)
- Theoretical Computer Science 560, 62-81 (2014)
- Journal of Mathematical Cryptology 8 (3), 209-247 (2014)
Quantum sensing and metrology
Quantum sensors represent a significant part of quantum technologies and are used in a wide variety of fields. They are based on the control of individual quantum systems which react to external factors: the performances of these sensors thus exceed that of conventional systems in terms of resolution and sensitivity. Solid-state quantum sensors detect the electromagnetic field at the nanoscale or under extreme conditions and open new possibilities for radio-frequency signal processing and image formation. By using a quantum microwave field, magnetic resonance measurements reach the single spin. Atomic interferometers measure gravity with unparalleled sensitivity, which leads to inertial navigation devices with unprecedented performance.
These advances extend the revolution that quantum technologies have already initiated in measurement science, with atomic clocks and quantum electric standards based on the quantum Hall effect and the Josephson effect. All of them are extremely stable, reproducible and universal references, some for time measurements and others for electrical measurements. Based on physical constants, they are now all at the core of the International System of Units (SI). The current challenges concern the extension of their applications, of their use and their integration into measurement systems.
To learn more:
- L. Rondin, J.-P. Tetienne, T. Hingant, J.-F. Roch, P. Maletinsky, and V. Jacques, “Magnetometry with nitrogen-vacancy defects in diamond”, Reports on Progress in Physics 77, 056503 (2014).
- M. Chipaux, L. Toraille, C. Larat, L.Morvan,S. Pezzagna, J. Meijer, and T. Debuisschert, Appl. Phys. Lett. 107, 233502 (2015).
- A. Bienfait, P. Campagne-Ibarcq, A.H. Kiilerich, X. Zhou, S. Probst, J. J. Pla, T. Schenkel, D. Vion, D. Esteve, J.J.L. Morton, K. Moelmer, and P. Bertet, Phys. Rev. X 7, 041011 (2017).
Quantum light plays an essential role in many quantum technologies. The single photon is the basic brick for the future quantum Internet and entangled photons are key for secure long-distance communications. Quantum photonics is also a very promising perspective for quantum computation, as it makes it possible to overcome decoherence problems, to perform calculations at room temperature and to use conventional techniques of optical nanotechnologies in order to create large-scale processors.
In Paris-Saclay, in the 1980s, Alain Aspect and his team worked on the violation of Bell’s inequality and demonstrated the existence of non-local quantum correlations for the first time with pairs of photons.
Today, Paris-Saclay is leading in optical quantum technologies, whether it be in the development of the basic bricks for communications and quantum computation or in the time-frequency metrology and in ultimate sensors. This is visible with the new generation of sources of single photons, which has now reached the commercial phase (see www.quandela.com), the development of effective photon-photon interactions for optical logic gates based on Rydberg atoms or on solid-state spins and for the integrated platforms for communication protocols and continuous variables quantum computation.
To learn more:
- Physical review letters 49, 91 (1982)
- Physical review letters 47, 460 (1981)
- Nature 466, 217 (2010)
- Nature Photonics 10, 340 (2016)
- Physical Review Letters 117, 253602 (2016)
- Phys. Rev. A 96, 053822 (2017)
- Nature Nanotechnology 12, 663 (2017)
- Phys. Rev. Lett. 120, 043601 (2018)
Quantum electrical circuits
Discovering that a quantum computer could perform computational tasks much more efficiently than a conventional computer initiated intense research to create the elementary bricks, the well-known quantum bits or qubits, and then to assemble them in order to demonstrate quantum algorithms. The illustration above shows from left to right the first superconducting quantum bit, for which the coherent superposition of the two states I0> and I1> was prepared in the early 2000s in Paris-Saclay; an elementary quantum processor based on four superconducting qubits; an electron cloud around an impurity spin in an insulator that could provide a high-performance qubit, and a microwave system to control and measure it. Many types of quantum electrical circuits are currently the subject of intense research within Université Paris-Saclay.
To learn more:
- Quantum Computation and Quantum Information, M. A. Nielsen & I. L. Chuang, Cambridge University Press (2010)
- Vion et al., Science 296, 886 (2002)
- A. Bienfait et al., Nature 531, 74 (2016)
- M. Kapfer et al., Science 363, 846 (2019)
Spintronics is a vast field of research which includes the exploration of new materials and physical phenomena involving a quantum property of electrons, the spin. Paris-Saclay was the cradle of spintronics with the discovery of giant magnetoresistance in 1988. Since then, local researchers have made many pioneering contributions (6 Highly Cited Researchers 2018).
While spintronics has already had a significant practical impact on our daily lives (information storage, electronic memories, sensors), current research works make it possible to consider new significant technological breakthroughs (very low-power computing architectures, replacement of the CMOS transistor, new quantum materials...).
To learn more:
- Physical Review Letters, 61, 2472 (1988)
- Nature Materials, 6, 813 (2007)
- Nature, Vol. 547, 428 (2017)
- Nature, Vol. 565, 35 (2019)
- Nature Review Materials, 2, 17031 (2017)
- SpinTronicFactory Roadmap: A european community view, Sci.Tech.EU, quarterly 30, 114 (2019)
Over the past thirty years, significant progress has been made in the manipulation of individual quantum objects (photons, laser-cooled atoms, "artificial atoms" obtained by techniques of condensed matter physics...). A number of breakthroughs in this area took place on the Saclay plateau. By assembling individual quantum systems in a controlled manner and making them interact, it is now possible to create interacting N-body quantum systems in laboratories.
This makes it possible to simulate systems that are too complex to be solved by numerical methods, like those used in solid-state physics, but with new control and measurement possibilities. This area of quantum simulation is now booming and paves the way for applications in quantum chemistry, materials physics, but also to solve combinatorial optimisation problems, for example, which appear in many fields.
To learn more:
- N. Schlosser et al., Nature 411, 1024 (2001)
- J. Billy et al., Nature 453, 891 (2008)
- R. Chang et al., Phys. Rev. Lett. 117, 235303 (2016)
- H. Labuhn et al., Nature 534, 667 (2016)
- P. St-Jean et al., Nat. Photon. 11, 651 (2017)
- D. Barredo et al., Nature 571, 79 (2018)
Quantum and topological materials
Exploring new electronic or spin states is one of the very early foundations of quantum matter that will make future applications, which are often unpredictable, possible. Both on a theoretical and an experimental level, Université Paris-Saclay works on high critical temperature superconductivity – whose interpretation is not subject to time – exotic phases such as quantum spin liquids, new properties resulting from topology and spin-orbit coupling, multiferroic materials and 2D electron gases at the surface of oxides. This is done with a wide range of expertise: X-ray diffraction using synchrotron or neutron radiation, ARPES, NMR, µSR, transport, magnetometry, etc. The presence of great tools such as the Synchrotron SOLEIL on the Saclay plateau is an exceptional asset to carry out this research.
New fundamental concepts have also emerged at the submicron scales of condensed matter, based on the knowledge of nanofabrication techniques. The aim is to understand and theoretically describe electronic and thermal transport in so-called mesoscopic systems, where the behaviour of electrons is determined by the quantum coherence of their wave function. Thanks to this work, it has been possible to make progress on problems related to the realisation of measurements which allow the rapid manipulation of quantum states in these systems while maintaining their coherence. New types of artificial atoms have appeared with the use of the properties and the flexibility of new nanostructured materials such as semiconductor or superconducting quantum dots as well as carbon nanotubes, graphene, topological insulators, etc. This guarantees a great flexibility in their use for the generation and manipulation of complex quantum states.
To learn more:
- Y.Imry, "Introduction to mesoscopic physics" Orford University Press (2002).
- E. Akkermans and G. Montambaux, "Mesoscopic Physics with electrons and photons", Cambridge University Press, (2007).
- Comptes Rendus Physique 17, 233 (2016): "Condensed matter physics in the 21st century: The legacy of Jacques Friedel"
- X. Montiel et al. Phys. Rev. B 95 (2017)
- J.C. Orain et al. Phys. Rev. Lett. 118, 237203 (2017).
- E. Kermarrec et al., Nature Com 8,14810 (2017).
- A.Santander et al., Nature Materials 13, 10850 (2014)
- E. Sivre et al.Nature Physics 14, 145 (2018).
- M. Ferrier et al.Phys. Rev. Lett. 118, 196803 (2017).
- M. Kapfer et al.Science 363, 846 (2019).
- F. Schrindler et al. Nat. Physics 14, 918 (2018).
Calculation languages and algorithms for quantum coprocessors
Despite the upcoming arrival of Exaflops supercomputers, some mobile applications will remain unavailable. Major players in computing (Google, Microsoft…) and high-performance computing (ATOS/BULL, IBM…) are thus working on the development of quantum coprocessors that provide access to quantum computing and memory resources, depending on the needs of the application. Our research focuses on the development of algorithms and software tools to use these future quantum coprocessors more specifically with:
- The definition of a programming language and a dedicated toolchain by applying them to concrete algorithms, in particular high-performance computing (HPC) algorithms;
- The development of quantum circuit synthesis tools using linear algebra and numerical optimization algorithms;
- The simulation of quantum algorithms on classical massively parallel architectures;
- The certification and validation of quantum programmes using formal methods;
- The exploration of classical-quantum interactions, both at the theoretical and practical level.
More information :
- T. Goubault de Brugière, M. Baboulin, B. Valiron, C. Allouche, Synthesizing quantum circuits via numerical optimization, Proceedings of ICCS 2019 (2019).
- A. Díaz-Caro, M. Guillermo, A. Miquel, B. Valiron. Realizability in the Unitary Sphere. Proceedings of the 24th Annual ACM/IEEE Symposium on Logic in Computer Science, LICS'19 (2019).
- C. Allouche, M. Baboulin, T. Goubault de Brugière, B. Valiron, Reuse methods for quantum circuits synthesis, Recent Advances in Mathematical and Statistical Methods, Springer-Verlag, Vol. 259, pp. 3-12 (2018).
- A. Scherer, B. Valiron, S.-C. Mau, Scott Alexander, E. van den Berg and T. E. Chapuran. Concrete resource analysis of the quantum linear-system algorithm used to compute the electromagnetic scattering cross section of a 2D target. Quantum Information Processing 16:60 (2017).
Research on quantum technologies has contributed to the emergence of remarkable expertise in terms of nanotechnologies and experimentation. Today, with the Centre for Nanosciences and Nanotechnologies, Université Paris-Saclay hosts one of the largest nanotechnology platforms in the world, where nearly 3,000 m² of cleanrooms are dedicated to academic research and to welcoming stakeholder (VSEs, SMEs and large groups). In addition, several laboratories of Paris-Saclay have created smaller nanofabrication workshops that allow the co-development of specific technological tools and advanced scientific programmes. This entire technological infrastructure is a unique asset for the Saclay plateau and guarantees its success both in terms of research and innovation.