Light and matter interactions are widely considered to be mediated solely by the electric field part of light, neglecting the other major component of electromagnetic waves. This is particularly relevant in quantum optics where the electric field component of the light couples to the electric dipole of a quantum system. However, the optical electric and magnetic fields carry the same amount of energy, leading to the conclusion that half of the interactions between light and matter are not studied. The reason limiting the observation of these interactions are two fold: (i) the weak amplitude and broad localisation of optical magnetic fields and (ii) the spatial overlap between electric and magnetic fields in far field. At the interface between nano and quantum optics, DarkLight develops a newly emerging field of research by extending the concept of optical nanoantennas toward the creation of strong hot spots of optical magnetic fields to (i) observe single magnetic dipole transitions, by (ii) strongly increasing their magnetic emission and (iii) enhancing the magnetic local density of states at the nanoscale. DarkLight introduces innovative photonic nanoantennas to tailor the “magnetic light”-matter interactions at the nanoscale. A pure, strong and confined magnetic hot spot of light is created by a photonic antenna and placed in close proximity to a quantum emitter carrying magnetic dipole transitions, increasing the emission of the latter dramatically. Moreover, this original optical antenna is placed at the end of a Near-Field Optical tip in order to fully control the positioning between the “magnetic” emitter and the nano-structure, allowing complete control of the interaction. This research program represents a new paradigm in the fundamental understanding of light and matter interactions and will open complete new horizons in research fields as diverse as nanotechnology, sensing, biology, quantum and molecular chiral optics, amongst other.

Solid state quantum emitters such as semiconductor quantum dots (QDs) have been successfully used as building blocks for photon-based quantum information processes. The majority of break-throughs, such as demonstration of indistinguishable single photon sources and optical generation, manipulation and read-out of spin qu-bits were initially demonstrated using epitaxially grown InAs/GaAs QDs. Recently, however, an alternative QD system : virtually strain-free GaAs/AlGaAs QDs fabricated by infilling of in-situ droplet etched nano-holes has been generating increasing interest with recent developements demonstrating that these dots can achieve close to radiative-limited linewidths and indistinguishable photon emission. Increasing the aluminum content in the AlGaAs barrier layers opens up the possibility of creating a novel indirect exciton, where the hole is confined in the QD, and the electron is confined in the X-valley of the AlGaAs barrier. This new QD system where the location of an electron can be controlled by a voltage to be either in one of the barriers or in the dot itself is an alternative to a QD molecule. We aim to to demonstrate an all-optical quantum teleportation procedure of an electron, initially prepared in the dot, towards one of the barriers by using a bi-chromatic optical excitation sequence implementing an adiabatic passage between two spatially separated states. Highly concentrated aluminum barriers also considerably slow down the decay of the QD nuclear spin magnetization. Using this new QD system which has low residual stress, we intend to manipulate the nuclear magnetization by exciting the dot with a surface acoustic wave (SAW) in order to switch on and store a precessional mode of the nuclear spins in the dot. The SAW transducer being deposited directly on the sample, this experiment integrates directly on the sample the driving radio-frequency excitation for nuclear spin manipulation to give an « on-chip NMR platform » for semiconductors.

This project considers the coupling of a single fluorescent nano-emitter with an optical cavity. The emitters are colloidal nanocrystals. Their emission can be tuned in the whole visible range, and they exhibit single-photon emission from cryogenic to room temperatures. The use of a new generation of nanocrystals with a CdSe core and a thick CdS shell will provide the photostability (absence of blinking) necessary to the project. An in-depth study of these nanocrystals will be performed : spectral properties at low temperature (coherence, spectral diffusion), nature of the emitting level (single or double dipole), emission polarization. The optical cavities will be micropillars of SiO2/TiO2 Bragg mirrors with a diameter of a few microns. The “deterministic” control of the spatial and spectral agreement between the emitter and the cavity mode is a crucial question. An efficient method has been demonstrated in 2008 to couple a quantum dot to a micropillar. It consists in locating, by fluorescence microscopy, an emitter in a planar cavity (Bragg mirrors) covered by a photoresist ; then exposing a disk of the resist, the diameter of which can be controlled through the exposure duration and is chosen in order for the micropillar mode to be resonant with the emitter ; then lift-off and etch the pillar. During this project, this fabrication activity will be started at the Institut de NanoSciences de Paris, with important adjustments (choice of materials, resist, exposure conditions….) to the case of colloidal nanocrystals. The weak nanocrystal-micropillar coupling will be evidenced through a modification of the emitting level lifetime (Purcell effect). By tuning the emission line width, thanks to the large range of temperatures available for nanocrystals, the role of decoherence and phonons for off-resonance coupling will be analyzed. This point is specific to solid-state cavity quantum electrodynamics is still not well understood for quantum dots and can be useful to ease the condition for spectral agreement. Finally, the emission coherence properties will be characterized and two-photon interference experiments will be performed.

The search for the next generation of spintronics devices will require the investigation of magnetization reversal by alternative techniques, on model and versatile materials. In this context, we propose to study how spin waves can be generated through surface acoustic waves with the idea of using them as information vectors, and also of rivalling some of the dynamic reversal effects currently evidenced in spintronics devices. More specifically, the goal of this experimental project is to study on a fundamental level the spin waves generated by strain in carefully chosen magnetostrictive materials. For this we will use the inverse magnetostrictive effect whereby magnetization is modified by application of strain. The strain will be applied in the form of surface acoustic waves (SAWs), generated either electrically using interdigitated combs, or optically using a laser to excite coherent phonons. While the former technique produces quasi-monochromatic strain plane waves and is regularly used on ferromagnets, the latter generates a broader frequency range and isotropic waves; it is very much a novel approach for magnetostrictive spin waves excitation. Magnetostrictive effects have been studied in a large range of materials: transition metals or rare-earth ferromagnets, garnets or DMS (dilute magnetic semiconductors), and are used in a number of everyday devices. We have chosen to focus on two different families of epitaxied thin films: (i) the ferromagnetic semiconductor Ga1-xMnxAs1-yPy, working at low temperatures but with well understood and fully adjustable magnetic properties, and (ii) Fe1-xGax (Galfenol), a highly magnetostrictive room-temperature ferromagnet. INSP (Institut des Nanosciences de Paris) has a long standing expertise on GaMnAs(P), and has recently succeeded in growing Galfenol in thin film form. When implemented dynamically, magnetostrictive effects are most efficient when the strain frequency matches the natural precession frequency of the ferromagnet. For this reason, and unlike most groups working in this field, we have chosen to work at resonance: first on GaMnAsP, whose low precession rates (

Self-assembled semiconductor quantum dots (QD) are very promising system to store and manipulate spin and also for photon-based quantum information. Their inherent quantum confinement enhances the coupling of optical excitations (i.e. excitons) and the spin degree of freedom carried by a single electron, hole and even a small number of nuclei within the QD. This project aims to study by optical means the spin and exciton properties of a new generation of unstrained semiconductor QD. We will show that these GaAs/AlGaAs QDs made by filling nano holes located at the surface of a GaAs surface, provide an ideal "nano-platform" to investigate fundamental and original condensed-matter issues, which are not accessible using the more commonly studied strained InAs/GaAs QDs. These fundamental studies addressed in this project could lead to important outcomes for opto-electronics, as well as opto-nuclear applications and for future implementation of quantum computation schemes. More precisely, we want to address two distinct novel topic taking advantage of the very particular properties of this new QD system : the first part is devoted to the investigation of the luminescence and coherence properties of the dark exciton state, and the second part concerns the control of the QD nuclear spins environnement and the investigation of the nuclear spin polarization from a single QD, acting as a nuclear spin emitter to the surrounding semiconductor matrix. These two topics are not only of fundamental interest, but also have potential applications in both quantum communication protocols and in biological science.