Seminars

Abstract
When confining photons in semiconductor lattices, it is possible to deeply modify their physical properties. Photons can behave as finite or even infinite mass particles, photons can propagate along edge states without back scattering, photons can become superfluid, photons can behave as interacting particles. These are just a few examples of properties that can be imprinted into fluids of light in semiconductor lattices.  Such manipulation of light present not only potential for applications in photonics, but also great promise for fundamental studies.  One can invent artificial media with  exotic physical properties at the single particle level or even more interestingly when interactions are considered.
During the talk, I will illustrate the variety of physical systems we can emulate with fluids of light by presenting a few recent experiments. Perspectives in terms of analog simulation of complex problems will be discussed.

Biography
Jacqueline Bloch is an experimental physicist, expert in non-linear and quantum optics in semiconductors. After a PhD on semiconductor quantum wires, she started a research program at CNRS on semiconductor microcavities. She has always been convinced that the physics of quantum fluids of light is particularly rich, in particular when taking full advantage of the technological tools available at the Center for Nanoscience and Nanotechnology. Along her carrier, she has explored a variety of physical phenomena, like superfluidity, solitons, flat bands, topology, phase transitions or analog black holes.

Jacqueline Bloch is today Research Director at CNRS, Professeure Chargée de Cours at Ecole Polytechnique and member of the French Academy of Science. She was awarded the 2015 Jean Ricard prize of the French Physical Society, the 2017 CNRS Silver Medal and the 2019 Ampère prize.

Keywords : microcavities, light matter interaction, polaritons, analog simulation, condensates

Registration : inscriptions.colloquia@c2n.upsaclay.fr

Seminars

International Research laboratory ELyTMaX

Engineering Science Lyon Tohoku, Materials and systems under extreme conditions

This presentation aims at showing the research activities held at ELyTMaX, and the collaboration possibilities with permanent researchers of Tohoku University in Japan.

ELyTMaX is an International Joint Unit (UMI) launched by CNRS, Université de Lyon (France) and Tohoku University (Japan). The Japan site of ELyTMaX is located at Tohoku University in Sendai, and regroups around 20 people (both from France and Japan) including Full Professors, Associate and Assistant Professors, postdoctoral fellows, double degree PhD, Master students and administrative staff.

ELyTMaX laboratory is conducting research in the engineering science research field, combining expertise from mechanical engineering, electrical engineering, material science and electrochemistry. As an international joint unit, joint expertise of Japanese and French researchers is gathered to investigate together material behavior, and to propose innovative solutions to monitor their lifetime.

The research conducted at ELyTMaX laboratory is both fundamental and applied research, and focuses on the behavior of materials (and the systems they form) under extreme and complex conditions (pressure, temperature, electromagnetic field, radiation, or highly corrosive environments).

In the view of predicting and extending lifetime of materials and structures, three main strategies are developed:

• Fabrication / Repair of the materials and systems, for minimizing or recovering from their degradation,

• Investigation of the behavior of materials, when subjected to complex solicitations or environments, including both structural materials and smart materials,

• Monitoring of the structural health of materials and systems, through Non Destructive Techniques.

These three main strategies are supported by multi-physics and multi-scale modeling, for better understanding physical-chemical insights of materials and systems behavior.

The typical application field is the energy industry (e.g. electrical power plants), transportation and medical devices. The strategy is refined notably through scientific questionings coming from the applications, where the type of degradation of materials which are studied comes from practical cases.

https://www.elyt-lab.com/en/content/elytmax-umi-3757

Seminars

This talk will provide a broad overview of ongoing research in my group and specifically focus on two topics: phase change material (PCM) enabled reconfigurable photonics, and free-form micro-optical couplers for photonic packaging. On the first topic, we leverage the giant optical refractive index modulation (exceeding unity) concurrent with solid-state phase transition in PCMs to create a cohort of tunable photonic structures, including ultra-compact and electrically driven nonvolatile phase shifters, transient photonic structures that can
be made ‘invisible’ on-demand, and zoom lenses with no moving parts. On the latter topic, we discuss an universal optical interface that can be adapted to chip-to-fiber, chip-to-chip and chip-to-free-space coupling with remarkable low insertion loss (0.5 dB) and large bandwidth (> 300 nm) performance.

Juejun (JJ) Hu is currently the John F. Elliott Professor of Materials Science and Engineering at MIT. He holds a Ph.D. degree (2009) from MIT and a B.S. degree (2004) from Tsinghua University, China, both in Materials Science and Engineering. Prior to joining MIT, Hu was an Assistant Professor at the University of Delaware from 2010 to 2014. Hu’s primary research interest covers new optical materials exemplified by chalcogenide compounds, as well as enhanced photonmatter interactions in nanophotonic structures. He has authored and coauthored over 150 refereed journal publications and technologies developed in his lab have led to several spin-off companies. Hu has been recognized with the SPIE Early Career Achievement Award, the Robert L. Coble Award from the American Ceramic Society, the Vittorio Gottardi Prize from the International Commission on Glass, the DARPA Young Faculty Award, and the NSF CAREER Award, among others. He is a fellow of Optica (formerly OSA) and the American Ceramic Society.

Seminars

Hybrid systems combining both cavity electrodynamics and cavity optomechanics have been theoretically proposed, with predictions of cooling at the single-polariton level. Cavity optomechanics with exciton-polariton Bose-Einstein condensates opens intriguing perspectives, particularly in view of the potential access to an optomechanical strong-coupling regime, and the possibility of using vibrations to actuate on such a macroscopic quantum fluid. These ideas are at the backbone of our main research in collaboration with the Paul Drude Institut in Berlin. Here I will discuss some of the collaboration experimental and theoretical latest results in which phonon-lasing [1],  a parametric oscillator for phonons [2,3], and polariton lattices’ neighbor sites showing phonon-induced asynchronous locking [4], are demonstrated.  

[1] Polariton-driven phonon laser, D. L. Chafatinos, A. S. Kuznetsov, S. Anguiano, A. E. Bruchhausen, A A. Reynoso, K. Biermann, P. V. Santos, A. Fainstein, Nat. Commun. 11, 4552 (2020). 

[2] Optomechanical parametric oscillation of a quantum light-fluid lattice, A. A. Reynoso, G. Usaj, D. L. Chafatinos, F. Mangussi, A. E. Bruchhausen, A S. Kuznetsov, K. Biermann, P. V. Santos, A. Fainstein, Phys. Rev. B 105, 195310 (2022), Featured in Physics and Editors' Suggestion. 

[3] A parametric Oscillator for phonons, M. Stephens, Physics 15, s20 (2022).

[4] Metamaterials of Fluids of Light and Sound, D. L. Chafatinos, A. S. Kuznetsov, P. Sesin, I. Papuccio, A. A. Reynoso, A. E. Bruchhausen, G. Usaj, K. Biermann, P V. Santos, A. Fainstein, arXiv:2112.00458 (2021)

Seminars

Until the 2000s, it was assumed that the Antarctic ice sheet, because of its large size, would not contribute to sea level on a century scale. Satellite observations have dramatically changed this perspective by revealing that Antarctica is rapidly losing ice. I will present our most recent understanding of the atmosphere-ocean-ice interactions that led to the recent changes in Antarctica, and outline why Antarctica now represents the most uncertain contribution to sea level rise at the end of the 21st century. Finally, I will take a step back to present how we are reconstructing past climate variability with a combination of ice cores, innovative instrumentation and atmospheric modeling.

Cécile Agosta is a climate scientist specialized in Antarctic studies and snow-atmosphere interactions. She obtained her PhD at the Institut des Géosciences de l'Environnement (Université de Grenoble, France), and continued her researches at the University of Liège, Belgium, where she specialized in polar atmosphere modelling. She is now a researcher at the Laboratoire de Sciences du Climat et de l’Environnement (LSCE, Paris-Saclay, France) in an experimental team to interpret Antarctic water vapor and snow isotopic composition with a model-data approach.

Seminar given in the framework of the EUGLOH Alliance/ SMART-22 project

Link: https://us02web.zoom.us/j/86277738532

Seminars

In this talk, we give an overview of the main mechanisms occurring during nanoparticles formation in non-thermal plasmas especially when microwave excitation is used. This work aims at addressing questions about the formation of carbon or tungsten dust nanoparticles in fusion devices (tokamak).

The kinetic pathways leading to nanoparticle will be described from experimental observations using complementary gas-phase spectroscopic diagnostics coupled with ex-situ analyses of nanoparticle size distribution, density and morphology. The discussion based on experimental results will be supported by briefly introducing some models developed specifically to get insights in the complex physico-chemistry involved in nanoparticle formation in non-equilibrium plasmas.

Karim Ouaras is a CNRS researcher at LPICM, working in plasma processing for III-V epitaxy. He obtained his PhD in plasma science from University Sorbonne Paris Nord (LSPM lab) in 2016. After his PhD, he did several post-docs around plasma physics, gas phase spectroscopy and material science (carbon, tungsten, silicon, polymers), successively at University Paris Sud - Orsay; LPICM; Stanford University and University of Cambridge). To date, he has published 20 peer-reviewed articles.

Figure caption: Example of a SEM micrograph showing carbon nanoparticles deposited on Si substrate using Ar:C₂H₂ plasma process.

Seminars

The performance of artificial intelligence (AI) technologies has improved significantly over the last decade in such a way that AI is now everywhere in our daily life via software neural networks. However, this continual growth in computational performance of these networks comes with large increases in the computational time and energy needed to train them. Developing AI at the hardware level has the potential to bend this curve and provide fast and lower energy computing. In this talk, I will present a new hybrid magnetic-superconducting device that can be used as an artificial synapse in neuromorphic circuits. The device is a magnetic Josephson Junction that consists of a barrier of magnetic nanoclusters between two Nb electrodes. The critical current of these junctions can be tuned by varying the magnetic order of the clusters, which can be used to perform synaptic weighting. I will describe the properties of the MJJ and show that its synaptic properties can be obtained in different material systems with an energy cost as low as 10^-19J. Finally, I will present circuit simulations where MJJs are included in a neural network for image recognition operating at speeds over 100 GHz, and show some preliminary experimental validation of the simulations..

Seminars

Gaussian states appear naturally in quantum optics under the guise of coherent, squeezed, or thermal states. In particular squeezing is an important resource for the deterministic generation of large entangled states useful for quantum computation. Yet, Gaussian states have an important limitation: all Gaussian measurements on Gaussian states can be efficiently simulated i.e nothing specifically quantum is happening. In many quantum technologies, we thus require non-Gaussian states.A common route to create non-Gaussian states in quantum optics is by performing non-Gaussian measurements (often photon counting) on parts of a Gaussian state. I will therefore present a general way to describe such conditionally generated states. The resulting set of non-Gaussian states is vast compared to the well-characterized corpus of Gaussian states and it is thus interesting  to quantify this non-Gaussianity. I will argue in favour of negativity of the Wigner function as a figure of merit, based on its important role in sampling problems. I will then circle back to the conditional preparation scheme to show how Wigner negativity is fundamentally intertwined with quantum correlations.

Ref : https://doi.org/10.1103/PRXQuantum.2.030204

Mattia Walschaers got his PhD from the universities of Freiburg (Germany) and Leuven (Belgium) for a cotutelle project, supervised by Andreas Buchleitner and Mark Fannes. His work initially focused on the role of quantum effects in photosynthesis, where he developed analytically solvable toy models to better understand the role of disorder in coherent transport of photosynthetic excitons. Later on, his interest shifted to many-particle systems and many-particle interference a phenomenon which induced by indistinguishability of quantum particles. This ultimately led to the development of an experimentally implementable statistical benchmark for boson sampling.
The resulting dissertation was published as a book in the Springer Theses series, and it was also one of the four nominees for the SAMOP dissertation prize of the German Physical Society. Between 2016 and 2019 , Mattia was a post-doctoral researcher in multimode quantum optics group of the Laboratoire Kastler Brossel, where his research interests shifted to continuous-variable quantum optics and quantum information where he studied experimentally feasible non-Gaussian states and developed a general framework to study multimode photon addition and subtraction. Mattia has been a CNRS researcher at the LKB since 2019 where he is studying multimode non-Gaussian quantum states, quantum correlations in CV systems, quantum batteries, complex quantum networks, and applications of machine learning in quantum experiments

Seminars

After approximately 100 years of engineering computers, humans have reached performance that rivals biological brains in many ways, while exceeding it in sheer number-crunching capacity. Yet, we took a very different path from biology, and there remains a huge advantage in energy-efficiency for biological information processing systems. I will discuss our work to copy some of biology's tricks to build more efficient computers and tackle some of today’s hardest problems. This means re-visiting the design of computers from the bottom (devices) all the way up (algorithms). In one area, we are exploring computers augmented with “associative memories” for storing and retrieving complex patterns at low area and power consumption. Such an alternative to RAM speeds-up operations in genomics, security, and tree-based machine learning. In another area, we use the stochastic analog operations in neural network dynamics to more quickly find the solutions to intractable Optimization problems, forecasting significant improvement over traditional and emerging compute technologies. Finally, if time permits, I will describe the precision challenges that computing in analog systems poses, and the potential for methods such as analog error-correcting coding.

John Paul Strachan

Peter Grünberg Institute (PGI-14), Neuromorphic Compute Nodes, Forschungszentrum Jülich GmbH, Jülich, Germany,RWTH Aachen University, Aachen, Germany                                  

John Paul Strachan directs the Peter Grünberg Institute on Neuromorphic Compute Nodes (PGI-14) at Forschungszentrum Jülich and is a Professor at RWTH Aachen.  Previously he led the Emerging Accelerators team as a Distinguished Technologist at Hewlett Packard Labs, HPE. His teams explore novel types of hardware accelerators using emerging device technologies, with expertise spanning materials, device physics, circuits, architectures, benchmarking and building prototype systems. Applications of interest include machine learning, network security, and optimization. John Paul has degrees in physics and electrical engineering from MIT and a PhD in applied physics from Stanford University. He has over 50 patents, has authored or co-authored over 90 peer-reviewed papers. He previously worked on nanomagnetic devices for memory for which he was awarded the Falicov Award from the American Vacuum Society, and has developed sensing systems for precision agriculture in a company which he co-founded.

Seminars

One major road towards the development of efficient photonic quantum technologies would be to rely on unitary deterministic photon-photon interactions. However, optical photons do not interact naturally. One thus has to use light-matter interactions to find ways towards effective photon-photon interactions. In the last decade, two approaches have been developed to achieve strong photon-photon interactions with cold atoms. On one side, experiments featuring a single atom strongly coupled to a cavity have a strong nonlinearity enabling the realization of quantum logic gates between two photons. On another side, experiments mapping photons onto Rydberg excitations in a cold atomic gas can also achieve strong photon-photon interactions. Nevertheless, both approaches are bounded by either technical or physical limits, keeping them far from ideal unitary deterministic photonic interactions.  

In a novel apparatus, we combine these two approaches to overcome their limitations. I will present the first building blocks for quantum engineering of light with an intracavity single Rydberg superatom. We implement a coherent control of this superatom via a two-photon Rabi driving. The state of the superatom can be optically detected via the cavity transmission with a 95% efficiency. Finally, we demonstrate that our coupled system induces a 180° phase shift on the light reflected off of the cavity dependent on the superatom’s state. This 180° phase rotation, together with the coherent control and the single-shot state detection, is a key ingredient for the implementation of unitary deterministic photon-photon interactions, paving the way towards quantum optics applications.

Sébastien Garcia worked on the development of fiber interfaces between single atoms and single optical photons during his PhD under the direction of Prof. Reichel at Laboratoire Kastler Brossel, Ecole Normale Supérieure (2011-2015).  He did his first postdoc at Quantum Device Lab of Prof. Wallraff at ETH Zurich, mostly focusing on the detection of Rydberg atoms with superconducting microwave cavities (2016-2018). He is now a postdoc at College de France in the group of A. Ourjoumtsev. Here, his researches are dedicated on one side to, and on the other side to the realization of photon-photon interactions via Rydberg atoms in an optical cavity.