Seminars

Quantum imaging harnesses quantum properties of light and their interaction with the environment to go beyond the limits of classical imaging or to implement unique imaging modalities. In conventional quantum imaging systems, a non-classical state of light illuminates an object from which an image is formed on a set of photodetectors. In this respect, sources of entangled photon pairs are very prolific. Over the last decades, they have been used to achieve super-resolution [1] and sub-shot-noise imaging [2], as well as to develop new imaging approaches such as ghost imaging [3], quantum illumination [4] and quantum holography [5].

However, most of these experimental schemes require to measure intensity correlations between many spatial positions in parallel, a task that is much more delicate than forming an image by photon accumulation. Originally, this was performed using raster-scanning single-pixel single-photon detectors, but this process is very photon inefficient and time-consuming. In recent years, these systems were substituted by single-photon sensitive cameras, such as electron multiplied charge coupled device (EMCCD), to achieve faster quantum imaging with photon pairs and move this field closer to practical applications [6,7].

In this presentation, I will detail the technique that we have developed to image entangled photon pairs using cameras. I will then describe some specific approaches that were implemented thanks to this novel imaging ability, including quantum image distillation [4] and entanglement-enabled quantum holography [5]. Finally, I will discuss the perspectives and general interest of developing quantum imaging system based on entangled photon pairs.

[1] Boto, Agedi N., et al. "Quantum interferometric optical lithography: exploiting entanglement to beat the diffraction limit." Physical Review Letters 85.13 (2000): 2733.

[2] Brida, Giorgio, Marco Genovese, and I. Ruo Berchera. "Experimental realization of sub-shot-noise quantum imaging." Nature Photonics 4.4 (2010): 227-230.

[3] Pittman, Todd B., et al. "Optical imaging by means of two-photon quantum entanglement." Physical Review A 52.5 (1995): R3429.

[4] Defienne, Hugo, et al. "Quantum image distillation." Science advances 5.10 (2019): eaax0307.

[5] Defienne, Hugo, et al. "Polarization entanglement-enabled quantum holography." Nature Physics 17, 591-597 (2021).

[6] Moreau, Paul-Antoine, et al. "Realization of the purely spatial Einstein-Podolsky-Rosen paradox in full-field images of spontaneous parametric down-conversion." Physical Review A 86.1 (2012): 010101.

[7] Edgar, Matthew P., et al. "Imaging high-dimensional spatial entanglement with a camera." Nature communications 3.1 (2012): 1-6.

Seminars

Biological nervous systems have been a source of inspiration for realizing new computing paradigms in electronics and optical systems for decades. While the single operation of current traditional CMOS technologies is approaching the energy consumption (~1 pW) of the most basic operation in biological nervous systems, an action potential, the action potential is far from being the most fundamental operation in a living cell. At the heart of molecular biology is the central dogma, which describes how genetic information is sequentially transferred from DNA into RNA into proteins that are used for all cellular life. The nano-machine that translates mRNA into proteins is the ribosome and in the past twenty years there have been enormous developments in understanding its biological functionality. Its energy consumption is ~5 orders of magnitude smaller than an action potential and approaches the Landauer limit of computation, but its use as an inspiration for new computing paradigms is still in its infancy. This is most likely because an understanding of how energy is used to realize translation is still not well understood. In this talk, I present an alternative way to model the dynamics of the ribosome using network theory. This concise representation can be used to track dynamic changes in different ribosomal states and understand its global dynamical nature. I describe some of the differences between ribosome functionality and artificially realized nano-machines.

Figure : Heatmap of correlations between the interactions in 6 different files. (perfect correlation/decorrelation = 0/1).

Link : https://us02web.zoom.us/j/86277738532 -Find a clickable link in the attached file bellow

Seminars

The field of nanotechnology is booming, significantly impacting our society and creating a growing enthusiasm in biotechnology and biomedical science. During this seminar, I will therefore present 3 research projects in which nanoparticles play a central role, whether in the understanding of a biological phenomenon or in the development of diagnostic tools. 1) Understanding of the toxicity induced by inhaled nanoparticles After inhalation, nanoparticles can reach the pulmonary alveoli, where gas is exchanged. They then encounter the pulmonary surfactant, i.e. the fluid lining the epithelial cells. In this work, the interaction of model bare nanoparticles (latex, metal oxides, silica) with a biomimetic pulmonary fluid (composed of phospholipids and proteins assembled in vesicles) was studied and we showed that this interaction was of electrostatic origin. We also observed a wide variety of resulting hybrid structures, which attests to the complexity of the phospholipid/particle interaction. In addition, we succeeded in formulating particles covered with a supported bilayer derived from pulmonary surfactant and exhibiting remarkable stability in biological environment. Finally, the role of the pulmonary surfactant on the interactions between nanoparticles and alveolar epithelial cells was studied, demonstrating the importance of the pulmonary surfactant in the protection of the alveolar epithelium. 2) Conception of a dosimeter doped with gold nanoparticles for radiotherapy
With the latest generation of radiation therapy devices, no dosimeter can be used to achieve a satisfactory in vivo dosimetry. In this respect, we aimed to develop a new dosimeter based on gold nanoparticles.
We first quantified the degradation of conventional dyes (here azo dyes) under gamma irradiation, thus producing a reference dosimeter. We then synthetized gold nanoparticles and added them to dye solutions since they are known to increase radical production. Unexpectedly, an overall decrease of sensitization was observed. We demonstrated that this phenomenon was probably due to the dye propensity to adsorb onto the gold nanoparticles and to the fact that the radicals overproduced by nanoparticles preferentially attack dyes adsorbed at their surface.
Our results underlined the need for an in-depth physicochemical characterization of the dye/nanoparticle systems to reveal the mechanisms underlying their gamma irradiation.
3) Development of antigenic tests based on luminescent nanoparticles
The simple, rapid, portable, and specific detection of biomolecules and pathogens in complex media is of growing interest in many fields. Lateral Flow Assays (LFAs), and more specifically antigen tests, are a central tool in this context. However, the standard gold nanoparticle-based LFAs lack sensitivity and generally do not provide quantitative measurements or simultaneous detection of multiple targets.
In order to overcome these limitations, we combined a simple homemade reader coupled to a smartphone with the remarkable optical properties of lanthanide ions using luminescent nanoparticles as probes. We first demonstrated a gain in sensitivity of more than one order of magnitude compared to the reference LFA when detecting staphylococcal enterotoxins, approaching or surpassing the ELISA sensitivity for these biomolecules. Then, three toxins were simultaneously detected without any loss of sensitivity. Our method thus constitutes a powerful approach to detect multiple proteins and could be the basis of future sensitive and portable bioassays or diagnostic tests.

Link: https://cnrs.zoom.us/j/93699481150?pwd=VVRwMkhKMXUrMWxsN3RkNkxxeC96Zz09

Seminars

Nonlinear optics describes the behaviour of light in a nonlinear medium, exploiting higher orders of the material susceptibility. It allows us to, for example, change the colour of a light beam, change its shape or process light with light. Nonlinear optical phenomena are the basis of many devices used in optical communication systems, optical sensing or material research and enable a wide range of novel applications, and the need for the integration of nonlinear functionalities to the chip scale is evident

It is now well established that silicon nitride offers many advantages for integrated nonlinear photonics. Pushed by recent progress in fabrication, we now have access to very low loss waveguides while maintaining large flexibility in terms of dispersion engineering, both essential for the design of efficient nonlinear systems. As such many nonlinear optical demonstrations, mainly based on 3^rd order effects in the telecom band, have been performed. Pushing the applications over the entire accessible spectral range of silicon nitride, from the visible to the middle infrared, as well as offering completely new horizon of applications by inducing effective 2^nd-order effects, would provide new and essential elements to the nonlinear integrated photonic toolbox. In this talk I will quickly review our work on systems based on the inherent 3^rd order effects, and we then cover how we can leverage all-optical poling to enhance the typically weak 2^nd-order nonlinearities of the platform.

Camille-Sophie Brès is an associate professor at EPFL in the institute of Electrical Engineering. She received her bachelor degree with honors in electrical engineering from McGill University, Canada, in 2002. She then moved to the USA where she obtained her PhD in electrical engineering from Princeton University in 2006. After a post-doctoral position at the University of California San Diego she joined EPFL as a tenure track professor and director of the Photonic Systems Laboratory in 2011. Her work focusses on leveraging and enhancing nonlinear processes in optical waveguides for the optimization of all-optical signal processing, light generation and sensing by exploiting dispersion engineering, material properties, and architectural features. She was awarded the early career Women in Photonics Award from the European Optical Society in 2016, as well as ERC starting (2012), Consolidator (2017) and Proof of Concept (2019) grants.

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

Seminars

Perovskite oxides are technologically interesting because of their strong structure-property coupling, with interesting functional properties ranging from ferromagnetism, ferroelectricity to high-temperature superconductivity. Here I will give an overview of our work on synthesis of atomically smooth (111)-oriented oxides and discuss the effect of crystalline facet on growth and control of functional properties. Epitaxial thin films and heterostructures of antiferromagnetic (AF) LaFeO₃, ferromagnetic La_0.7Sr_0.3MnO₃ are used as model system. I will especially focus on how anisotropic strain engineering permits to tailor the AF Neel vector in epitaxial single crystalline LaFeO₃ thin films. To impose anisotropic strain, we rely on the (111) pseudocubic facet of orthorhombic scandate- and gallate-based oxide substrates. X-ray studies confirm a lowering of LaFeO₃ symmetry, from orthorhombic in bulk to monoclinic or triclinic, depending on the choice of substrate and the magnitude of anisotropic strain, in thin films, in accordance with DFT calculations. Epitaxial engineering allows us to efficiently tune the magnetic anisotropy from bi-axial in bulk to uniaxial in our thin films, as inferred from soft x-ray spectroscopy. By increasing the LaFeO₃ thickness transition of the uniaxial spin direction takes place, a change from an out-of-plane to an in-plane AF spin axis above 16 d₁₁₁-layers. I will also discuss the possibilities that anisotropic strain engineering offers to tune the interface AF spin texture between LaFeO₃ and a ferromagnet in a deterministic fashion, as confirmed by soft x-ray spectroscopy and spin-polarized neutron reflectivity. To probe the interface spin texture between LaFeO₃ and La_0.7Sr_0.3MnO₃ a combined soft x-ray spectroscopy, neutron reflectometry, magnetometry, TEM and DFT study was performed, and correlations between local AF order and concurrent structural reconstructions at interfaces will be addressed.

Professor Tybell has ~20 years of experience in oxide electronics materials science, and co-founder of the oxide electronics group at NTNU. He focuses on synthesis and nanostructuring of epitaxial complex oxide thin heterostructures and superlattices. Present research includes interface engineering of ferroelectric and magnetic systems, and the possibility for symmetry engineering of functional properties. Parallel to research he has devoted effort to teaching and administration and has had the responsibility to direct and develop a cross-disciplinary nanotechnology effort at NTNU and developed a new 5-year curriculum for the MSc study program within electronic systems design and innovation. Currently he is deputy director of Department of Electronics and Telecommunications with responsibility for research.

find a clickable link in the attached file bellow

Seminars

Light-matter interactions in condensed media at room-temperature are fundamentally limited by electron-phonon coupling. For instance, while the excitation cross-section of an isolated atom, or of a single quantum emitter at cryogenic temperatures, can reach one half of the wavelength of light squared (meaning that ~50% of incoming photons will interact for a diffraction-limited excitation); this value is reduced by 6-7 orders of magnitude for a fluorescent molecule or for a colloidal quantum dot at room temperature because of homogeneous phonon broadening. In order to render the exceptional optical properties of single quantum systems (such as single-photon emission and nonlinearities) efficiently accessible at room temperature and in condensed media, it is essential to enhance and optimize these interaction cross-sections.

Over the last two decades, plasmonic resonators have shown amazing promise towards this goal thanks to their ability to enhance optical fields by several orders of magnitude in deeply sub-wavelength volumes. However, the nanoscale dimensions of these field enhancements or “hot-spots” mean that it is extremely difficult to exploit them in a controlled and reproducible way. At Institut Langevin, we develop two approaches in order to achieve this:

-We introduce, in a deterministic way, a controlled number of quantum emitters in the nanoscale hot-spot between two gold nanoparticles using a DNA-based self-assembly strategy. Using this approach, we were able to enhance single-photon emission from fluorescent molecules by more than two orders of magnitude in a weak-coupling regime. I will discuss recent experiments where we reach a strong-coupling regime between a plasmonic resonator and five organic molecules.

-We actively control the seemingly random plasmonic hot-spots featured by disordered gold surfaces using far-field wavefront shaping. In practice, by tuning the phase of a pulsed excitation, we ensure the constructive interference of plasmonic modes that are delocalized over several microns on the surface; leading to a local enhancement of the nonlinear luminescence of gold by more than two orders of magnitude.

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

Find a clickable link in the attached file below

Seminars

Experimental methods allowing for the detection of single spins in the solid-state, which were initially developed for quantum information science, open new avenues for the development of highly sensitive quantum sensors. In that context, the electronic spin of a single nitrogen-vacancy (NV) defect in diamond can be used as an atomic-sized magnetometer, providing an unprecedented combination of spatial resolution and magnetic sensitivity under ambient conditions. In this talk, I will illustrate how scanning-NV magnetometry can be used as a powerful tool for exploring condensed-matter physics, focusing on chiral spin textures in antiferromagnetic materials.

Dr. Vincent Jacques is a CNRS research associate in the team “Solid-state quantum technologies” at the Laboratoire Charles Coulomb (Montpellier). His research interests cover several fundamental and applied topics related to the applications of “artificial atoms” in quantum technologies. Such topics include quantum optics, spin physics, and quantum sensing with the development of highly-sensitive magnetometers based on NV defects.

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

Find a clickable link in the attached file below