Under electromagnetic excitation, metal nano-objects can support collective electron oscillations, known as plasmon waves . When illuminated with white light, a resonance (Localised Surface Plasmon Resonance, LSPR) whose center and width, typically a few tens of nanometres, depend on the dielectric constant of the metal, the shape of the nanoparticle and on the dielectric environment of the nanoparticle. This property makes it possible to create sensitive sensors based on the detection of LSPR resonance shifts when the nanoparticle's environment changes. However, the sensitivity of these sensors is limited by the width of the LSPR resonance. To increase sensitivity, these nanoparticles can be positioned as a lattice on a substrate. Given the periodicity of this arrangement, the first order diffraction of incident light at a given wavelength can propagate in the plane of the array resulting in a much thinner resonance used to increase the sensitivity of the sensor. This resonance is called Surface Lattice Resonance (SLR). As part of this internship, we will fabricate arrays of gold nanoparticles above a gold mirrors, enabling us to observe collective resonance of such antennas lattice. We will characterize them optically and optimize the parameters to maximize the signal and its spectral finesse. In a second step, we will deposit CdSe/CdS quantum dots that resonate or do not resonate with the SLR modes, and study how their emission is modified by the resonance

CdSe/CdS core/shell quantum dots are excellent bright nano-emitters. At room temperature, under low excitation power they behave as high quantum efficiency single photon source thanks to efficient Auger processes leading to the recombination of a single exciton. They can be analysed as a simple two-level system. However, by increasing the excitation power, emission spectrum broadens dramatically. The two- levels system paradigm fails for interpreting those features. We have developed a model based on the radiative recombination of multiple excitonic levels within a single nanocrystal , relying on statistical description of electron and hole populations in a quasi-equilibrium and Bayesian analysis. Patch plasmonic nanoantennas consist of a thin dielectric medium sandwiched between a thick gold layer and gold patch.We have demonstrated that for a quantum dot inside such antenna, the absorption cross section is increased by 3 order of magnitude. Therefore such an antenna/ quantum dot system is a good candidate for achieving strong coupling. During the internship, the student will start developing bright optical nanosources by coupling nanoemitters to plasmonic antennas. He/she will fabricate then and study by confocal optical microscopy the fluorescence ( emission rate and spectrum, directivity,…). The final objective is to achieve the regime of strong coupling regime. Thanks to a high confinement and excitation, the emitters should gain specific original quantum properties.

In nanophotonics and quantum technologies, photon sources are a ressource which can be integrated into a chip. Cylindrical dielectric microdisks make excellent resonators in which optical gallery modes can propagate at the air/dielectric interface. Using optical lithography, we have fabricated gallery-mode resonators on which we have deposited fluorescent nano-emitters, colloidal quantum dots. These are CdS/CdSe/CdS semiconductors in a spherical core/shell/shell configuration. Of nanometric dimensions, their fluorescence wavelength depends on their size. They can emit single photons, are resistant to photobleaching and are bright under strong excitation. We have deposited these quantum dots in high concentration on microdisks, in order to achieve a sufficient gain. We were therefore able to create gallery modes excitonic microlasers. The aim of this internship will be to study these gallery-mode lasers, as a function of their size, shape or when two cavities are coupled. In particular, we will be interested in the behavior of these lasers far from the threshold, when the excitation laser is intense. Under these conditions, the resonant gallery mode intensity is high. If its coupling to the excitons is sufficiently strong, emission will be modified by exciton-photon interaction. We will study these strong coupling configurations in relation to theoretical predictions.

! Internship in a laboratory of mathematics ! How can quantum information be preserved in a system with thermal excitations? In certain fermionic chains, Majorana modes localized at the ends provide boundary degrees of freedom that can retain information for very long times. The internship will investigate the mathematical mechanisms underlying this dynamical stability at nonzero temperature, through the study of strong zero modes and their prethermal counterparts

Magnetic skyrmions are nanoscale spin textures whose collective dynamics may exhibit quantum effects. In frustrated magnets, their helicity, the angle describing the orientation of the in-plane spins, can behave as a quantum degree of freedom. Discrete energy levels and tunnelling between helicity configurations have motivated proposals for skyrmion qubits. How can these quantum properties be detected? This theoretical internship will explore this question using a nitrogen-vacancy (NV) centre in diamond as a local spin sensor. Fluctuations of the skyrmion's magnetic field modify the sensor's relaxation time, providing access to the spectrum of helicity fluctuations. The student will combine analytical calculations with numerical simulations to calculate helicity energy levels, transition matrix elements and the resulting NV relaxation rate. We will investigate how temperature, magnetic field, and sensor geometry affect the signal, and assess which features could distinguish quantum dynamics from classical thermal fluctuations. The project offers training in quantum magnetism, quantum sensing, and open quantum systems. Knowledge of quantum mechanics and basic programming skills are expected.

Atomic beams lie at the very foundation of most measurements in atomic physics. Rydberg atoms, in turn, are central to a wide range of challenges: quantum control, sensing, charge exchange, and the production of ion and/or electron beams. The proposed project aims to optimize an atomic beam, relying for instance on microchannels, which should significantly improve the beam collimation. Other techniques, such as magnetic compression or transverse (2D) laser cooling and guiding, may also be investigated. The goal is to obtain an intense, dense Cs or Rb atomic beam in the Rydberg excitation region. The experiment will then be transferred to different setups, such as an innovative electron microscope, the HREELM (High-Resolution Electron Energy Loss Microscope). This microscope detects very low-energy electrons with excellent time resolution. The objective is to exploit the space-time correlation between a Rydberg atom and its electron, obtained by ionizing the atom, in order to improve the electron source.

At the Langevin Institute, we leverage rare-earth-doped crystals (e.g., Tm:YAG, Er:YSO) as powerful platforms for quantum sensing, memories, and analog signal processing. These materials, operated at cryogenic temperatures (~3K), offer exceptional optical linewidths, long population lifetimes, and strong light-matter interactions, key for quantum coherence. However, commercial cryogenics introduce vibrations and thermal loads, degrading performance. This internship explores alternative matrices (YGG, co-doped crystals, molecular crystals, ceramics, waveguides) to extend lifetimes, damp vibrations, and optimize light guiding, enabling lower ion concentrations and reduced decoherence. The intern will use advanced spectroscopy (photon echo, spectral hole-burning) to characterize these materials. Ideal for M1/M2 or engineering students in optics/physics with experimental skills. Collaborative project with IRCP and Thales.

Photons are great carriers of information but they usually don’t interact with one another. Atoms interact but are hard to manipulate and do not benefit from the toolbox of quantum optics for detecting quantum fluctuations and entanglement. Many approaches have been proposed to marry these two systems for quantum simulation of condensed matter with strongly interacting photons, but to date, the realization of large-scale synthetic materials made of optical photons is still missing. Our team targets this exciting goal, namely the creation of Synthetic Photonic Matter. We are offering an internship opportunity (followed by an ERC-funded PhD) to expand the capabilities of this platform to a new level by increasing by many orders of magnitude the effective photon-photon interactions and enter the strong interaction regime.

Les photons sont d’excellents porteurs d’information, mais ils n’interagissent généralement pas les uns avec les autres. Les atomes interagissent, mais ils sont difficiles à manipuler et ne bénéficient pas de l’arsenal de l’optique quantique pour d´etecter les fluctuations quantiques et l’intrication. De nombreuses approches ont été proposées pour marier ces deux systèmes en vue de simuler de la matière condensée avec des photons fortement interagissant, mais à ce jour, la réalisation de matériaux synthétiques composés de photons fait encore d´efaut. Notre équipe vise cet objectif ambitieux, à savoir la création de Matiere Photonique Synthétique. Nous proposons une opportunité de stage (suivie d'une thèse financée par l'ERC) pour étendre les capacités de notre plateforme à un nouveau niveau en augmentant de plusieurs ordres de grandeur les interactions effectives photon-photon et en entrant dans le régime des interactions fortes.

Quantum computing requires precise control of individual quantum systems and their interactions. Ultracold molecules offer long-lived quantum states for storing information, while Rydberg atoms provide strong interactions for fast quantum operations. Combining these advantages opens a new route towards scalable quantum computing. Our group is developing an experimental platform combining individual CaF molecules and Rb atoms in reconfigurable optical tweezer arrays. The long-term goal is to exploit molecule–Rydberg atom interactions to implement fast quantum gates and new methods for manipulating and measuring molecular qubits. During this six-month internship, the student will contribute to the development and characterisation of the hybrid experimental platform. Depending on experimental progress and the student's interests, the work may focus on optical tweezer generation and control, single-particle trapping and imaging, Rydberg excitation, or the development of experimental control and data analysis techniques. The student will work closely with researchers developing this new quantum computing platform.

When high energy photons are absorbed in a material, carriers are photo-generated with a large of kinetic energy above the band edge. In some well-tailored devices, it is possible to slow down carrier relaxation such that carriers form a “hot” distribution that may offer a pathway to very high efficiency of solar energy conversion. Two positions are available . The internships will have experimental and theoretical sides, and will be carried out in the framework of the ERC ULTIMATEPV.

The central objective of this internship is to establish a reproducible route for fabricating europium molecular membranes and, crucially, to determine whether their exceptional optical properties are preserved after exfoliation and transfer. The student will optimize the mechanical exfoliation conditions to increase the yield of thin, large-area flakes; develop deterministic dry-transfer protocols onto photonic substrates such as SiC, SiO2/Si and glass; characterize membrane thickness, morphology and crystalline quality using optical interference microscopy, atomic force microscopy and Raman spectroscopy; and investigate their luminescence and optical homogeneous linewidths at cryogenic temperatures using spectral hole burning. Comparison with bulk crystals will allow the influence of exfoliation, reduced thickness and substrate coupling on the optical coherence of the molecular material to be established.

This internship will focus on measuring mid-infrared molecular transitions of methanol (CH3OH), ammonia (NH3), and other molecules known for their enhanced sensitivity to changes in µ. The work will involve achieving subDoppler spectroscopic resolution to reach target laboratory frequency accuracies of ~100 Hz needed for comparisons with astronomical observations. This activity is part of the ANR Ultiµos project, a collaborative effort which seeks to refine current constraints on the possible variation of µ which involves leading research institutions, including Laboratoire Kastler Brossel (LKB, L. Hilico) and MONARIS (C. Janssen) at Sorbonne Université. The three partners of the Ultiµos consortium will collaborate to conduct measurements in different spectral windows, to identify transitions as targets for future Earth/space comparison campaigns, which could further tighten constraints on variations of µ. Other collaborators, such as Vrije Universiteit Amsterdam and Onsala Space Observatory, will provide theoretical and observational/astronomical support to complement the experimental efforts.

The master student will join the effort at LPL to develop a new-generation compact and versatile microwave (MW) spectrometer operating over the 2–20 GHz range. This instrument is conceived both as a high-sensitivity detector of internal quantum states in polyatomic molecules and as a precision tool for molecular frequency metrology. The spectrometer will enable cross-checks between MW rotational frequencies and mid-infrared (MIR) rovibrational data planned to be measured at the 100 Hz level in the frame of the ANR Ultiµos project. These comparisons are directly motivated by the search for potential variations of the proton-to-electron mass ratio µ, a fundamental constant whose stability can be tested by confronting laboratory data with MW astronomical spectra of molecules such as methanol and ammonia. These species possess transitions with strong sensitivity coefficients to µ, making them powerful probes of possible temporal or spatial variations of fundamental constants. In Ultiµos, spectroscopy with ultrastable MIR quantum cascade lasers provide ultra-precise MIR frequencies with relative uncertainties of 10 ¹². By using combination–difference schemes, these MIR data yield effective MW intervals that can be directly confronted with our SI-traceable MW measurements. Such dual determinations, based on entirely different experimental chains and affected by distinct systematic effects, are ideal for robust cross-validation of frequency values and uncertainty budgets.

The goal of this internship is to develop and characterize nonlinear acousto-optic devices operating in the mid-infrared (wavelength of 3-8µm), leveraging broadband transparency and piezoelectricity of III-V semiconductor heterostructures. These devices will perform phase modulation, but also potentially on-chip optical routing, a pre-requisite for magnetic field-free optical isolation. The internship will be mostly experimental, involving the use and development of two existing setups. The first one is a mid-IR integrated photonic bench allowing to characterize the operation of the devices (see above, right). The second one is a heterodyne interferometer, that allows to image the SAW-related vibration (amplitude and phase) of the sample surface to characterize the acoustic properties of the devices (see above, left).