CMQED group

Matéo Vernet

2025-10-20T07:28:49Z

Granular superconductors like Nb and NbN and how they can be used to create tunable quantum circuits.

Matéo Vernet has an engineering degree from ESPCI Paris and a master's degree in Physics of Complex Systems from Université Paris Cité. His research focuses on granular superconductors, such as niobium (Nb) and niobium nitride (NbN) thin films. Combining ion irradiation and electrostatic gating, he studies how geometrical disorder, magnetic impurities, and electrostatic fields change the micro- and macroscopic quantum behavior. In addition, his research encompasses a theoretical approach based on the localization landscape, which will offer novel insights into the spatial inhomogeneity and emergence of superconductivity in disordered and structured systems.

Thomas Krieguer

Alexis — 2025-10-20T07:28:42Z

Thomas Krieguer is a PhD student in quantum physics with a Master's degree in Quantum Light-Matter and Nanotechnologies from Paris-Saclay University. With expertise in open quantum systems, non-linear physics, and light-matter interaction, Thomas's research is centered on developing a fully fermionic theoretical model to explore ultra-strong coupling between cavity-mode light and electronic subbands. This advanced model goes beyond the rotating wave approximation to study complex phenomena such as polaritons, the dynamical Casimir effect, and the Bloch-Siegert shift, contributing significantly to the understanding of non-linear generation in cavity-coupled electronic subbands. Thomas's work not only enhances theoretical insights but also aids in predicting and optimizing the responsivity of quantum cascade photodetectors. His model is frequently applied to highly doped semiconductor heterostructures embedded in patch cavities, particularly in quantum cascade detectors, to deepen understanding of electronic transport mechanisms and support the development of enhanced device designs.

Qian Li

Alexis — 2025-10-20T07:28:33Z

QianLI has a background in material science, after getting her bachelor and master degrees in China, now she is a PhD student in ESPCI. Qian's research focuses on the development of high-temperature, ultra-fast Superconducting Nanowire Single Photon Detectors (SNSPDs) based on BSCCO (Bi2Sr2CaCu2O8+x), a van der Waals type-II high-temperature superconductor. Her work aims to fabricate large-area BSCCO flakes on borosilicate glass using anodic bonding technic and to integrate them with silver optical waveguides, finally develops an SNSPD that operates above 30K.

Dmitry Yakovlev

Alexis — 2025-10-20T07:28:25Z

Dr. Dmitry Yakovlev, currently a Postdoctoral Researcher at École supérieure de physique et de chimie industrielles de la Ville de Paris (ESPCI), specializes in condensed matter physics, focusing on superconducting quantum phenomena. With a PhD. from Higher school of Economics (HSE), his expertise spans nanofabrication, quantum computing, and Josephson junctions. Dmitry has contributed to advancements in superconducting single photon detectors and hybrid superconducting systems, and enjoys football, skiing, and diving.

Francesco Pisani

Alexis — 2025-10-20T07:28:17Z

Master degree in Plasma Physics and doctorate in Solid State Physics at the University of Pisa. During his postdoctoral research, he was deeply involved in the design, fabrication, and characterization of heterostructures, nano-cavities and metamaterials ; the primary goal being the development of a quantum cascade detector for THz and Mid-IR range, operating in the strong light-matter coupling regime. His expertise comprise measuring the electronic transport by means of spectroscopic techniques : transmission ; absorption ; reflectivity and photocurrent measurements. He was responsible for the fabrication of all the devices in the cleanroom, including lithography of nanostructures and the chemical and dry etching steps. He also contributed in developing a theoretical model to predict the responsivity of these detectors, aiming to further optimize their performance. He also performed multiple simulations involving finite element electromagnetic solvers and Schrödinger-Poisson solver to optimize both the band structure and cavity design.

Sergei Kozlov

Alexis — 2024-11-05T09:03:14Z

Educated at the Moscow State University at the faculty of Physical and Chemical Engineering. He started his first research steps in the Institute of Solid State Physics in Chernogolovka in the field of bose-condensation of interwell excitons but continued in the laboratory of superconductivity where he studied transport phenomena in nanowires. Then he did his PhD at ESPCI where he studied the critical behaviour of superconducting nanowires under the supervision of Dimitri Roditchev & Chéryl Feuillet-Palma. Now he is postdoc in the group CoQED studying the dynamics of Abrikosov vortices.

Alexis Jouan

Alexis — 2024-11-03T11:20:00Z

Alexis Jouan is an expert in superconductivity in mesoscopic systems. He performs high frequency measurements up to 100GHz to study the properties of electronic systems at cryogenic temperatures. He did a postdoc at the University of Sydney where he worked on the fabrication of topological Josephson junction in InAs quantum wells and performed new readout methods for spin qubits in Silicon. He also worked on the Fluxonium, a superconducting qubit during his postdoc in the quantum circuit group at ENS Lyon.

His research is focused on the study of quantum coherences in condensed matter physics. He designs, manipulate and measure electronic systems at very low temperature. Currently, he's working on new THz spectroscopy techniques based on superconducting circuits for the study of fundamental excitations in ferromagnetic materials or superconducting materials.

Yanko Todorov

Alexis — 2024-08-29T21:45:00Z

My research focuses on extreme electromagnetic regimes in optoelectronic devices operating in the mid- and far-infrared spectral domain (wavelength = 5 μm-300 μm, "TeraHertz"). In these structures a multitude of electrons trapped in artificial quantum potentials are ultra-strongly coupled with photons confined in microcavities or electromagnetic metamaterials. These structures allowed me to demonstrate and study the ultra-strong light-matter coupling regime in the THz domain for the first time. These studies led to new superradiant infrared emitters with high radiative performance and fast modulation speeds. They also provided new ultra-low noise infrared quantum detectors operating at high temperature with performance beyond the state of the art.
Today, I am particularly interested in the new quantum correlations that appear in this regime. I wonder about the possibilities of designing new experiments and optoelectronic devices where these quantum effects can be observed. In the long term, this activity should bring new insights into the field of quantum mechanics and enrich quantum technologies with new concepts.

After completing his secondary education in Bulgaria, Yanko Todorov arrived in France in 1997 to pursue his higher education in preparatory class at the Lycée Louis Le Grand. He studied in Ecole Normale Supérieure (Paris) in 1999-2001, and completed his doctoral thesis in 2006 at the Laboratory of Photonics and Nanostructure in Marcoussis (now C2N Laboratory). He then joined the QUAD team at the Laboratory of Materials and Quantum Phenomena (Université Paris Diderot) as a post-doc (2007-2009), and then CNRS researcher (2009-2019). After returning at ENS as a CNRS researcher (2019-2024), Yanko Todorov integrated Physics and Materials Laboratory (LPEM) at École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris, ESPCI. There, Yanko Todorov co-founded the research group Condensed Matter Electrodynamics together with Alexis Jouan and Cheryl Feuillet-Palma.
Yanko Todorov's research focuses on the exploration of light-matter interaction in quantum devices operating in the mid- and far-infrared range. Among his notable achievements are : the study of the Purcell effect with quantum cascade emitters [1], the first experimental demonstration of the ultra-strong light-matter coupling regime in the TeraHertz domain [2], a new quantum description of collective phenomena related to ultra-strong coupling [3,4,5], as well as the demonstration of microcavity enhanced quantum detectors [6]. His worm also covers metamaterial architectures [7], both for unipolar devices [8] and optomechanical applications [9, 10].

Milestones :
2024 -present : CNRS Director of Research (DR-CNRS)
June 2020 : Defence of Habilitation à Diriger les Recherche (HDR) : “Exploring light-matter interaction at the nanoscale with infrared photons”
September 2019 : ERC Consolidator Grant “UNIQUE” (2020 – 2026)
2009 - 2024 : CNRS Researcher (CR-CNRS)
2007 – 2009 : Post-doctoral Research Associate/ Laboratoire de Matériaux et Phénomènes Quantiques, University Paris -Diderot, Paris, France
2006 – 2007 : Temporary Lecturer and Research Assistant/ Laboratoire de Matériaux et Phénomènes Quantiques, University Paris -Diderot / Paris/France
2002 - 2006 : PhD : Laboratory of Photonics and Nanostructures/University Paris VI/ France
2002 : Master (Quantum Physics), Ecole Doctorale 107, Ecole Normale Supérieur (Ulm)/Paris / France
1999-2002 : Bachelor's Degree at Ecole Normale Supérieure (Paris)
1997-1999 : Lycée Louis le Grand (Paris)

Selected Publications :
[1] “Purcell Enhancement of Spontaneous Emission from Quantum Cascades Inside Mirror-Grating Metal Cavities at THz Frequencies”, Y. Todorov, I. Sagnes, I. Abram and C. Minot, Phys. Rev. Lett. 99, 22 3603 (2007).
[2] “Ultrastrong Light-Matter Coupling Regime with Polariton Dots” , Y. Todorov, A. M. Andrews, R. Colombelli, S. De Liberato, C. Ciuti, P. Klang, G. Strasser, and C. Sirtori, Phys. Rev. Lett. 105, 196402 (2010).
[3] “Dipolar quantum electrodynamics theory of the three-dimensional electron gas”, Yanko Todorov, Phys. Rev. B 89, 075115 (2014).
[4] “Dipolar quantum electrodynamics of the two-dimensional electron gas”, Yanko Todorov, Phys. Rev. B 91, 125409 (2015).
[5] “Electronic transport driven by collective light-matter coupled states in a quantum device”
Francesco Pisani, Djamal Gacemi, Angela Vasanelli, Lianhe Li, Alexander Giles Davies, Edmund Linfield, Carlo Sirtori, and Yanko Todorov, Nature Communications 14, 3914 (2023).
[6] “Room temperature 9µm photodetectors and GHz heterodyne receivers”, D. Palaferri, Y. Todorov, A. Bigioli, A. Mottaghizadeh, D. Gacemi, A. Calabrese, A. Vasanelli, L. Li, A. G. Davies, E. H. Linfield, F. Kapsalidis, M. Beck, J. Faist, C. Sirtori, Nature 556 (7699), 85 (2018)
[7] “Absorption engineering in an ultra-subwavelength quantum system”, M. Jeannin, T. Bonazzi, D. Gacemi, A. Vasanelli, L. H Li, A. G. Davies, E. Linfield, C. Sirtori, and Y. Todorov, Nano Letters 20 (6) 4430–4436 (2020).
[8] “High temperature metamaterial TeraHertz quantum detector”, M. Jeannin, T. Bonazzi, D. Gacemi, A. Vasanelli, S. Suffit, L. Li, A. G. Davies, E. Linfield, C. Sirtori and Y. Todorov, Appl. Phys. Lett. 117, 251102 (2020).
[9] “Actively tunable laser action in GeSn nanomechanical oscillators”, Hyo-Jun Joo, Jiawen Liu, Melvina Chen, Daniel Burt, Baptiste Chomet, Youngmin Kim, Xuncheng Shi, Kunze Lu, Lin Zhang, Zoran Ikonic, Young-Ik Sohn, Chuan Seng Tan, Djamal Gacemi, Angela Vasanelli, Carlo Sirtori, Yanko Todorov, Donguk Nam, Nature Nanotechnology, 19, pages1116–1121 (2024).
[10] “Optomechanical terahertz detection with single meta-atom resonator”, C. Belacel, Y. Todorov, S. Barbieri, D. Gacemi, I. Favero, C. Sirtori, Nature Communications 8 (1), 1578 (2017).

Cheryl Feuillet-Palma

, Alexis — 2024-08-29T21:33:00Z

In 2001, a new kind of detection principle was developed using an ultra-thin NbN superconducting nanowire. These detectors were soon on the market. Despite the strong interest generated by their unrivalled performance at very low temperatures, many questions remain unanswered, such as the in-depth understanding of the mechanism underlying the matter-radiation interaction, and the possibility of creating these detectors from any type of superconducting material. It is in this perspective that my recent work and forthcoming experiments are focused, on devices based on ultra-fine high-temperature superconductors. The main objectives are to produce high-Tc superconductor nanowires, YBa2Cu3O7-δ and Bi2Sr2CaCu2O8+δ, to propose a single-photon detector operating at moderate cryogenic temperatures, and to study the microscopic detection mechanism. To carry out this work, I was awarded an ANR JCJC Hector (High Temperature Superconductors for single photon detection). Part of my work concerns the broadband microwave response of a Bi2Sr2CaCu2O8+δ monolayer controlled by electrostatic field effect. Another part concerns recent work on the realization of resonant cavities in YBa2Cu3O7-δ, which will make it possible to realize kinetic inductance detectors in cuprate, or to measure the current-phase relationship in an RF SQUID.

After studying at the Ecole Normale Supérieure, Cheryl Feuillet-Palma carried out her experimental thesis work in the mesoscopic physics group at LPENS.
During her thesis, C. Feuillet-Palma focused on quantum effects in spin-polarized transport. This internationally competitive subject required both extensive experimental expertise in sample fabrication (nanotube growth and electron nanolithography) and low-noise current measurements (Nat. Phys. 2009), as well as a theoretical approach generalizing to spin-dependent transport in Landauer-Büttiker scattering matrices. Her work has enabled her to demonstrate that, for the first time, the orbital phase of the electron wavefunction can be coupled with spin. This artificial spin-orbit coupling offers new methods for manipulating electronic spin in nanostructures, a significant step in the field of quantum information. She continued her training with a post-doc at the Paris-Cité University. Her research focused on the study of signatures in the transport of light-matter coupling in semiconductor structures inserted in double-metal cavities. She has developed a new type of very sub-wavelength THz optical cavities, enabling the strength of light-matter coupling to be increased to ultra-strong coupling. Since December 2011, C. Feuillet-Palma has been an associate professor at LPEM, ESPCI. Her work focuses on nanometric devices based on thin-film superconductors.