(en anglais) Light interaction with nanoresonatorsCentre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
Resonators, be it plasmonic, photonic, micro or pico, are triggering the development of various applications in nanooptics, from quantum information processing, plasmon-assisted lasing, to nanosensing of biomolecules.
The properties of cavities, of any kind, are due to their intrinsic natural resonance modes. Because of dissipation, either by absorption or leakage in the open space, the modes have a finite lifetime. They are eigenstates of a non-Hermitian operator, here the Maxwell’s equations.
Two characteristic parameters, which figure prominently in the physics and device applications of cavities, quantify the capability of cavity modes to boost light-matter interactions, the quality factor Q and the mode volume V.
It is therefore important to be familiar with the modes, their Qs, their Vs, their excitation rate by plane waves or near-field sources, their perturbation by tiny objects ... Usually, all these concepts are well comprehended in the limit of Hermitian physics. We will revisit them substantially in the framework of non-Hermitian physics, trying to answer questions such as: how we partition the LDOS between Q and V? Is the definition of Q so evident? Why V should be complex valued? What is the signification of Im(V)?
Philippe Lalanne (CNRS) is an international expert in computational & nanoscale electrodynamics. With his colleagues, he has elaborated powerful modal theories for gratings, photonic-crystal waveguides and nanoresonators. This helped him providing deep insight into key nanoscale optical phenomena and devices, e.g. confinement in photonic-crystal cavities and extraordinary optical transmission, and demonstrating novel nanostructures with record performance in their time, e.g. broadband photon sources, slow-light injectors. Noteworthy, he has pioneered the development of metalenses by arraying nanopillars that impart a local phase shift as a function of their dimension. This allowed the demonstration of the first flat optical elements with high efficiency and large-NA.
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(en anglais) First C2N Colloquium: "From Einstein’s questions to quantum information: a new quantum revolution"Centre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
Abstract: In 1935, with co-authors Podolsky and Rosen, Einstein discovered a weird quantum situation, in which particles in a pair are so strongly correlated that Schrödinger called them “entangled”. By analyzing that situation, Einstein concluded that the quantum formalism is incomplete. Niels Bohr immediately opposed that conclusion, and the debate lasted until the death of these two giants of physics. In 1964, John Bell discovered that it is possible to settle the debate experimentally, by testing the now celebrated «Bell’s inequalities», and to show directly that the revolutionary concept of entanglement is indeed a reality. A long series of experiments, started in 1972, yielded more and more precise results, in situations closer and closer to the ideal theoretical scheme. After explaining the debate, and describing some experiments, I will also show how this conceptual discussion has prompted the emergence of the new field of quantum information and quantum technologies.
Bio: Alain Aspect is a physicist, distinguished scientist and professor at Ecole Polytechnique and Institut d’Optique graduate School. Alain was the first to experimentally confirm the non-local character of quantum entanglement, a bizarre area of quantum mechanics that perplexed Einstein and many others. This understanding has led to applications of quantum mechanics beyond the lab scale, towards quantum computing and provably secure communications. Alain and his collaborators have also made breakthroughs in laser cooling of atoms, Bose-Einstein condensates, and cold atom simulation of the celebrated Anderson localization.
The seminar will be followed by a discussion between Alain Aspect and the students, and a lunch cocktail will be served in the C2N main hall.
(en anglais) Programming multiphoton entanglement: theory and practiceCentre de Nanosciences et de Nanotechnologies, A003, Palaiseau
Quantum computers promise a paradigm shift humanity’s information processing capability. Graph states are the predominant language of entanglement between qubits. Modern quantum error correction—a crucial component of large-scale quantum computation—relies centrally on graph state entanglement. Different graphs enable different computational tasks, and so the generation of arbitrary graph states is powerful.
Meanwhile, silicon quantum photonics is a high-performance, scalable quantum technology platform, boasting circuits of unparalleled size. However, integrated quantum photonics has so far been constrained to two on-chip generated photons. Here, we present the first device to wield four-photon entanglement, and measure high-visibility on-chip quantum interference. We also develop rules for the successful postselection of graph states, and probe which states are inaccessible. Further, we identify optimal photonic circuits capable of generating all accessible graph states up to 8 qubits. This provides an endgame strategy for the final era of postselected experiments, before heralded devices become a necessity.
On our silicon chip, four sources of spontaneous four-wave mixing generate two Bell pairs in four dual-rail qubits. These are entangled using a two-qubit gate, programmably generating either star- or line-type graph states. Reconfigurable single-qubit gates then access the remaining four-qubit graph states and implement projective measurements. Finally, the photons are routed off-chip to superconducting nanowire single photon detectors. Our star and line graph states have fidelities 0.78 ± 0.01 and 0.68 ± 0.02 respectively. Our results represent an important step on the road to truly scalable quantum photonics.
Jeremy's Ph.D thesis was focused on scaling up entanglement in integrated quantum photonics, via the generation of graph states---quantum states with ubiquitous application in quantum information protocols. In his thesis, he establishes rules for the successful postselection of linear optical experiments, and in doing so uncovers new, fundamental limitation of postselected gates and sources. Further, he demonstrated the first integrated device to generate four-photon entanglement in dual-rail qubits, overcoming the two-photon barrier. The silicon chip generated both types of four-qubit graph state on the same device (a first in optics) and demonstrated high visibility on-chip quantum interference. Jeremy is now a postdoc in QETLabs University of Bristol, working on integrated photonics for quantum information, graph state entanglement, and architectures for linear-optical quantum computing.
(en anglais) Ultrafast X-ray imaging of magnetic materialsCentre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
Spin transport is the key for reading or writing bits in spintronic devices by utilizing the Giant Magnetoresistance effect or the spin transfer torque effect. Spin currents have also been shown to play important role in the ultrafast manipulation of magnetization via all optical switching. Hence, detailed understanding of spin currents is a crucial step in development of spintronic devices. In this talk, I will describe our recent experimental studies using emerging synchrotron and free electron laser techniques that can probe these materials with both high spatial and temporal resolution. I will discuss our work on imaging spin dynamics in nano-devices and probing spin transport across ferromagnet/copper interface. We have developed an extremely sensitive spectro-microscopy detection method based on element specific x-ray magnetic circular dichroism to probe spin transport in Co/Cu devices. The sensitivity of this new ‘lock-in’ technique has allowed us to detect the extremely small transient Cu magnetization with sub 100 nm spatial resolution. This technique has also enabled imaging of nanoscale motion of localized nonlinear spin waves in spin torque oscillator, allowing a detailed insight into p-like character of localized spin-wave excitation. I will also discuss our recent work on ultrafast imaging following optical pumping at free electron laser sources.
Roopali Kukreja joined Materials Science and Engineering department at UC Davis as an Assistant Professor in Fall 2016. She received her B.S. in Metallurgical Engineering and Materials Science from the Indian Institute of Technology Bombay in 2008 and then her M.S. and Ph.D. degrees in Materials Science and Engineering from Stanford University in 2011 and 2014, respectively. Prior to her appointment at UC Davis, Kukreja worked as a postdoctoral researcher at the UC San Diego, with Profs. Oleg Shpyrko (Physics Department) and Eric Fullerton (Center for Magnetic Recording Research). Her research interests at UC Davis focuses on ultrafast dynamics in nanoscale magnetic and electronic materials, time resolved X-ray diffraction and imaging techniques, thin film deposition and device fabrication. She is recipient of Melvin P. Klein Scientific development award (2015), Air Force Young Investigator Award (2018) and Nuclear Regulatory Commission faculty development award (2019).
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(en anglais) Gravitational wave detection: a quantum experimentCentre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
Detecting gravitational waves required 4 decades of experimental effort to reach a sensitivity at the h~10-21 level, corresponding to mirror displacements below 10-18 m. Apart from classical noise (seismic noise, thermal noise...), it was realized as soon as in the late 70s that quantum fluctuations of the light field were responsible for the Standard Quantum Limit, a sensitivity limit that second-generation gravitational-wave interferometers such as Advanced Virgo and Advanced LIGO are about to reach. A number of ideas have been considered to beat the SQL: squeezed states of the light field, tailoring the optical response function or taking advantage of EPR correlations between two optical beams.
I will present the current status of the interferometers, how squeezed light is now routinely used to increase the range of Advanced Virgo and Advanced LIGO,and how further progress is required for the next generation of large-scale interferometers.
Pierre-François Cohadon joined what has become the Optomechanics and Quantum Measurement group at Laboratoire Kastler Brosselin 1996 to start graduate work. He was involved in the pioneering experiments performed at LKB: demonstration of feedback cooling of a mechanical resonator, demonstration of intracavity radiation pressure cooling, proof-of-principle demonstration of optomechanical correlations... For a few years, he has been involved in the Virgo project for the detection of gravitational waves, where investigatesthe use of squeezing to further increase the sensitivity of Advanced Virgo.
(en anglais) Magnetization Dynamics in Nanostructures and Thin FilmsCentre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
In the first part of my talk I will discuss the outstanding question in the broad field of spin dynamics with ferromagnets whether the damping of gyromagnetic precession is in actuality subject to finite size effects at the nanometer length scale. We demonstrate that the effective damping in nanomagnets depends strongly on the excited spin-wave mode and on the size of the nanomagnet. The damping constant a is a critical parameter for spintronics devices, e.g., spin-torque-transfer magnetic random-access memory (STT-MRAM). Optical measurements of the magnetization dynamics are particularly challenging when the diffraction-limited laser spot is much larger than the size of the nanomagnet. We developed a novel heterodyne magneto-optical microwave microscope (H-MOMM) to measure ferromagnetic resonance in individual, well-separated nanomagnets by use of heterodyne detection of magneto-optical signals at microwave frequencies. The experimental results are in good agreement with calculations based on the theory of dissipative transverse spin-currents internal to a conductive magnetic film, where the spin-currents are proportional to the spatial curvature of the excited mode , .
In the second part I will demonstrate how the Dzyaloshinskii-Moriya Interaction (DMI) can be directly determined from the frequency of propagating spin-waves. The DMI has recently attracted great interest as it is the origin of many chiral phenomena including chiral domain-walls and skyrmions. We quantified the DMI induced frequency-shift with Brillouin-Light-Scattering spectroscopy (BLS). I will present DMI measurements on several different multilayer systems. We demonstrated in a series of Ni80Fe20/Pt samples for a range of Ni80Fe20 thicknesses that the DMI is proportional to the Heisenberg exchange which has been predicted earlier by Fert  and Moriya  for metallic oxides and magnetic spin-glasses . In a second study we studied the influence of an oxide layer on the DMI in Cu/CoFe and Pt/CoFe samples. We found that an oxide layer increases the DMI . Finally, I will show results for a series of CoFeB/Cu(x)/Pt system, where we find that the DMI and the proximity magnetization in Pt are correlated.
 H.T. Nembach, J.M. Shaw, C.T. Boone and T.J. Silva, Physical Review Letters, 110, 117201 (2013), Highlight in Nature Nanotechnology 8, 227 (2013)
Hans T. Nembach is a Senior Research Associate at JILA, University of Colorado and Research Associate at the National Institute of Standards and Technology (NIST) in Boulder, Colorado. He received his PhD in physics from the Technical University Kaiserslautern, Germany in 2006, where he worked in the group of Prof. Burkhard Hillebrands. He began work at NIST in 2006 under the auspices of a DAAD postdoctoral fellowship. In 2015 he received the NIST Physical Measurement Laboratory Distinguished Associate Award. His research interests are magnetization dynamics in thin films, multilayers and magnetic nanostructures.
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(en anglais) Microfluidic devices for biomedical applications: from bioanalysis to artificial biomimetic organsCentre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
In this talk I will review some examples of microfluidic devices that can handle very small volumes of biological fluid for medical applications. In the field of biomedical analysis, current macroscopic methods based on chromatography techniques coupled to mass spectrometry remain long and tedious, which may prove detrimental for certain pathologies where a fast and early diagnosis is often desired. On-chip analytical methods are therefore very promising, since analysis can be carried out in 30 minutes with a microliter of biological liquid. In the first part of my talk, I will present two recent examples of bioanalytical chips for the detection of trace biomolecules: 1/ nanofluidic devices allowing enrichment by a factor of 1000 after few minutes in a selective way  and 2/ graphene-based biosensors for direct DNA electrochemical detection at the sub-femtomolar level [2-3].
More recently, microfluidics technologies are also used to develop “organs-on-chips” with living cells that are cultured within 3D devices. Concerning this recent emerging field, I will conclude my talk by presenting two novel microfluidic devices. The first one is an artificial lung that exhibits the largest surface area of gas exchange at 4 inches wafer scale  compared to previously reported devices. I will show that its oxygen transfer rate is strongly related to the thickness of the thin membrane inserted between both blood capillaries and air microchannels. The second device aims to develop a tumor-on-a-chip as an innovative 3D in vitro model of pancreatic cancer able to recreate the complex physiology of the tumor microenvironment and, more specifically, the blood vasculature around the spheroid.
 A-C Louër, A Plecis, A. Pallandre, J-C Galas, A. Estevez-Torres, A-M. Haghiri-Gosnet, Anal. Chem. 85 (2013) 7948−7956
 B. Zribi, E. Roy, A. Pallandre, S. Chebil, M. Koubaa, N. Mejri, H. Magdinier Gomez, C. Sola, H. Korri-Youssoufi, A-M Haghiri-Gosnet, Biomicrofluidics 10 (2016) 014115
 B. Zribi et al, Nanoscale 8 (2016) 15479 and B. Zribi et al, Carbon 153 (2019) 557-564
 A-M. Haghiri-Gosnet, Lyas Djeghlaf, Julie Lachaux, Alisier Paris, Gilgueng Hwang, European Patent EP18306405.4 (29 Oct. 2018) "Microfluidic gas exchange devices and methods for making same"
Anne-Marie Haghiri (CNRS, DR1) is co-leader of the “Microsystems and NanobioFluidics” Department at C2N (UMR9001). She has published 98 peer-reviewed articles (h index=37), 8 book chapters and 5 patents. In the last 10 years, she has coordinated 4 ANR projects and participated to 2 European projects. She is developing "soft" micro/nanostructuration of biocompatible materials for innovative microfluidic platforms as well as organs-on-chip (partner of RHU ANR BioArtLung H2020 project). She has an active interest in on-chip electrophoresis for early diagnosis as well as electrochemical detection of both DNA and proteins.
(en anglais) Interplay between Coulomb interaction and quantum coherence in electronic circuitsCentre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
Mesoscopic physics studies relatively large objects with properties that can only be described by quantum phenomena such as the particle-wave duality. Small electrical circuits cooled down to low temperature where billions of electrons behave as quantum particles, provide a prominent illustration. However, the electrons’ quantum character is generally limited to the micrometric scale because of Coulomb interaction with other nearby charges.
In this seminar, I will first show that it is possible to strongly reduce Coulomb interaction’s detrimental effect on quantum coherence by circuit engineering. Second, I will explain how to exploit Coulomb interaction to transfer the quantum state of electrons to indistinguishable electrons a few microns away.
Hadrien Duprez : Graduated from the École Polytechnique de Montréal in 2016, then obtained a masters degree on Quantum Devices at Université Paris Diderot in 2017. During his undergraduate studies, he was lucky to do a one year internship on 2D photonic crystal cavities for low-power laser application at NTT in Japan. He now is a 2nd year PhD student in the Quantum Physics in Circuits team at C2N.
(en anglais) Photon-phonon interaction driven by complexityCentre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
Precision is a virtue in science in general and nanotechnology in particular where carefully fabricated nanometer-scale devices hold great promise in both classical and quantum regimes. Ground-state cooling or phonon amplification require, for example, a sideband resolved photon-phonon coupling where unavoidable imperfections often impose severe performance limits. However, imperfection and disorder are ubiquitous in Nature and emerge with a role particularly important in nanoscale devices.
In this talk, I will explore the limits imposed by imperfection in different nanodevices, but not only. In certain cases, disorder may be invoked to enable new functionalities and can be exploited to enhance the light-matter interaction in different fields of nanotechnology such as quantum photonics, nonlinear photonics, phononics and optomechanics.
(en anglais) Reservoir computing using magnetic nano-dots system and Brownian computing using skyrmionsCentre de Nanosciences et de Nanotechnologies, Amphithéâtre, Palaiseau
First, I introduce our design of reservoir computer using MRAM technology. Then, I will talk about recent progresses in making Brownian computer using skyrmions.
Brownian computing is a method to perform calculation with ultra-low energy consumption.
Up to now, we have succeeded in making a Hub (branch of skyrmion channel) and in voltage control of the diffusion. Ratchet and C-join are also essential devices that we need to realize.