Statistical physics, a century-old theory, is probably one of the most powerful constructions of physics. It predicts that the equilibrium properties of any system composed of a large number of particles depend only on a handful of macroscopic parameters, no matter what the particles are and how they exactly interact with each other. But the question of how many-body systems relax towards such equilibrium states remains largely unsolved. This problem is especially acute for quantum systems, which evolve in a much larger configuration space than classical systems and obey fundamentally non-local equations of motion. Despite the formidable complexity of quantum dynamics, recent theoretical advances have put forward a remarkably simple picture: the dynamics of closed quantum many-body systems would be essentially local, meaning that it would always take a finite time for correlations between two distant regions of space to reach their equilibrium value. This form of locality would be an emergent property of the whole system, similar to spontaneous symmetry breaking, and have its origin in the propagation of quasi-particle excitations. The fact is, however, that only few observations to date directly confirm this scenario. In particular, the role played by the dimensionality of the system and the range of the inter-particle interaction is largely unknown. The concept of this project is to take advantage of the great versatility of ultra-cold atom systems to investigate experimentally the relaxation dynamics in regimes well beyond the boundaries of our current knowledge. We will focus our attention on two-dimensional systems in which the particles interact through both short- and long-range potentials, when all previous experiments were bound to one-dimensional systems. The realisation of the project will hinge on the construction of a new-generation quantum gas microscope experiment for strontium gases. Amongst the innovative experimental techniques that we will develop for this project is the electronic state hybridisation with Rydberg states, called Rydberg dressing, which will enable us to shape the interaction potential between the atoms.

Optical means for stimulating and monitoring neuronal activity have provided a lot of insight in neurophysiology lately toward our understanding on how brain works. Optogenetic actuators, calcium or voltage imaging probes and other molecular tools combined with advanced microscopies allowed ‘all-optical’ readout and manipulation of neural circuits. Yet, important challenges remain to be overcome to achieve full optical neuronal control, concerning reliable delivery and expression of sensors and actuators in the same neurons, elimination of cross-talk between the imaging and manipulation channels, and achieving recording and manipulation each with single-neuron and single-action-potential precision. SLALLOM is a concerted attempt between two academic (Wavefront-Engineering Microscopy group; WEM, Neurophotonics Lab. and Lasers group, Charles Fabry Laboratory; LCF) and two industrial partners (Amplitude Systemes; AS, ALPhANOV) aiming to remedy the last two challenges. The central idea of SLALLOM is to develop a novel single-light-source ‘all-optical’ two-photon computer-generated holography (CGH) microscope using an innovative frequency-converted dual-output directly diode pumped Thulium (Tm)-doped fiber amplifier for three-dimensional (3D) multicell excitation and monitoring. The proposed laser system aims at the disruption of current laser technology used for 2-photon imaging and activation in optogenetic studies. Indeed, mature laser technologies suffer from drawbacks (e.g. lack of energy, absence of repetition rate tunability, excitation wavelength not matching the 2-photon absorption spectra peak of most molecular tools) that prevent their use for massive parallelization of neuron manipulation. We therefore propose a cutting-edge dual-branch ultrafast fiber laser system operating in the 920-975 nm wavelength range. This laser system steps away from conventional laser technologies (e.g. Ti:sapphire laser, Ytterbium fiber laser) and builds upon frequency upconversion of Tm-doped ultrafast fiber amplifiers seeded by a frequency-shifted Erbium oscillator. The two branch parameters will be optimized for their respective goal: imaging with >5 W, 40 MHz and 100 fs and photoactivation with >5 W, 10 µJ and 100 fs. A 3D-CGH microscope appropriately modified for addressing a large excitation field, will be assembled together with a 2-photon scanning system for 3D structure or functional imaging of neuronal activity, with genetic reporters. The developed laser will be used as a single-laser source for both imaging and stimulation, aiming to treat the cross-talk between these modalities by exploiting the superior temporal resolution provided by CGH in combination with highly-efficient fast-kinetic opsins. The microscope will be used to follow brain complexity in the visual cortex in vivo at high spatiotemporal resolution. The project, led with the WEM group, forerunner in developing advanced optical methods for neuronal stimulation, gathers specific and complementary skills from four partners whose expertise is recognized at international level. The WEM group has proposed about ten years ago the application of spatiotemporal light patterning with CGH and temporal focusing as a means of precisely parallel targeting cells groups, enabling photostimulation at high spatio-temporal precision. LCF is widely acknowledged as a major actor of the research in diode-pumped ultrafast lasers. ALPhANOV is a French technological center specialized in the development of innovative high-power fiber laser, especially for ultra-short pulse amplification. Finally, AS is the world leading company providing integrated, industrial-grade ultrafast laser systems, and has a long-standing collaboration with LCF through a common laboratory. SLALLOM consortium will demonstrate a reliable ground-breaking ultrafast laser source adapted to a 3D-CGH microscope to study the brain activity in vivo at high spatiotemporal resolution with scientific and industrial outcomes.

Quantum Control attempts to apply and extend the principles already used for classical control systems to the quantum domain. In this way we hope to establish a control theory specifically dedicated to regulating quantum systems. This proposal addresses some key problems related to the control of open quantum systems by applying quantum feedback control. Open quantum systems are quantum systems in interaction with an environment. This interaction perturbs the system states and causes loss of information from the system to the environment. However by applying quantum feedback control, the system can “fight” against this loss of information. The main obstacle is that standard strategies from classical control are not immediately applicable to quantum systems. While there has been much development on the theoretical side, there remain key open questions concerning optimality, robustness, and best design methods for dealing with generic quantum models which can be implemented in concrete experiments with less difficulties. The first objective of Q-COAST is to develop more efficient and robust strategies for quantum feedback design applied to open quantum systems. As a second objective, we investigate the situation where the inputs are in non-classical states, the case where the generalization from the classical to the quantum case becomes more difficult. Such states are critically important for scalable quantum information processing. Our third objective is to go beyond the existing tools to design estimators and controllers. This will be achieved by introducing new pathways through the interaction between fields of quantum statistical mechanics, quantum information geometry, quantum filtering, and quantum feedback control. The final goal is to develop further numerical simulations of quantum components as well as implementing our proposed strategies in real experiments. The experimental implementations can be realized as the project will involve collaboration with leading experimental groups who have been successfully applying feedback control theoretic principles to actual quantum systems.

In this project, we will develop a new type of hybrid metal/semiconductor laser source exploiting the strong potential of optical Tamm modes. These modes, which have recently been highlighted in the optical domain, exist at the interface between a metal layer and a dielectric Bragg mirror. In our case, The Bragg mirror is containing quantum wells. These modes present many features that can be advantageously exploited both for the realization of photonic or plasmonic sources. Indeed, due to their hybrid metal/dielectric nature and to their particular dispersion relation, they should enable a coupling either to the optical modes in the light cone or directly to the plasmon mode. They also present much lower losses than conventional plasmons modes and can be controlled and laterally confined by a simple patterning of the metal layer. Finally, the metallic layer opens the way to the electrical injection of the structures for the realization of photonic or plasmonic integrated sources. From a fundamental point of view, this study is part of a general trend in plasmonics which aims to cut losses while maintaining key properties of plasmons (spatial localization, spontaneous emission enhancement, lasing). Three goals will be pursued in parallel: • The first goal is the demonstration of an electrically injected and laterally confined laser source. We will first focus on the demonstration and optimization of lasing under optical pumping in Tamm structures confined by a metallic disk. The amelioration of the optical properties of the structures associated to the confinement (quality factor, enhanced beta factor, reduction of laser threshold) will be studied experimentally but also by theoretical modeling. The design of the structures for the electrical injection will be developed in parallel. In a second step, the degree of freedom opened by the easy structuration of metals will be used to design refined geometries in order to control the polarization of the emitted light or to exploit gallery modes present in these structures. • The second goal is to form a bandgap in the Tamm dispersion relation by a periodic nano-structuration of the metallic layer only. Photonic crystal cavities will be realized in order to increase the field confinement without additional losses, control the emission direction and reduce the device size. This approach relies on a well mastered technology and induces no degradation of the active layer during the process since only the metal is patterned. Periodic Tamm structures will be modeled and characterized in order to evaluate the impact of the patterning on the emission properties of the structures, and optimize lasing in terms of threshold and emission directivity. • The third goal is to exploit the hybrid metal/dielectric nature of the Tamm modes as well as their compatibility with an electrical injection in order to develop surface plasmon sources. Two directions will be investigated: on the one hand a coupling between the Tamm and the plasmon mode via a grating on metal, and on the other hand a direct coupling between these two modes. Modeling and optical characterization will be implemented to identify and optimize the Tamm/plasmon coupling in both configurations, in order to finally exploit this coupling for the realization of plasmon sources. The realization of this project will not only lead to a better understanding of the physical effects associated with these new modes, but also pave the way both for the development of new types of laser structures whose properties could be controlled by simple technological processes, and to devices enabling the conversion of localized electrical excitation into surface plasmons.

Digital and analytical functions performed by today’s semiconductor devices are governed by the electronic transport across an engineered material system with a well-defined electronic structure. Even if a multitude of electrons are concerned in the device operation, the device fundamental characteristics arise from properties inherent to single electrons. For instance, photon emission is related to transitions between electronic states of the system and for optoelectronic devices operating in the mid and far infrared wavelength range is characterized by an extremely long spontaneous emission time (>100ns), which hinders the realization of efficient light emitting diodes. In this project we plan to realize novel optoelectronic devices, whose performances do not belong to single electron properties, but rather depend on the ensemble of the interacting carriers. We recently demonstrated that the optical properties of a dense electron gas do not reflect the energy spectrum, but depend on the Coulomb interaction between electrons. The absorption spectrum of a semiconductor quantum well with several occupied energy levels presents a single absorption peak at an energy completely different from the single particle transition energies. This unique optical resonance, concentrating the whole interaction with light, corresponds to a many-body excitation of the system, the “multisubband plasmon”, in which the dipole-dipole Coulomb interaction locks in phase the optically allowed transitions between confined states. In this project, the peculiar properties of multi-subband plasmons will be exploited for mid and far infrared optoelectronics. The first property is the fact that, as the permittivity of multisubband plasmons depends on the doping level and on the size of the quantum well, semiconductor layers with ad hoc dielectric properties (hence metamaterials) can be realized. As a first application we will design all-dielectric waveguides in the mid and far infrared for quantum cascade lasers. A second application will be the design of engineered infrared absorbers. The second part of the project is based on another fundamental property of collective electronic excitations: their superradiant nature. Indeed the multisubband plasmon is the bright state issued from the coherent superposition of several intersubband excitations. As a superradiant state can be visualized as one in which a macroscopic polarization is established over a region of space, a very interesting way to characterize this state will be its observation by using Electron Energy Loss Spectroscopy. The superradiant nature of multisubband plasmons results in a radiative lifetime of the order of few hundreds fs, thus much shorter than the typical intersubband spontaneous emission lifetime. We will exploit this property to conceive and realize two different classes of optoelectronic infrared emitters based on many-body excitations: - Quasi-monochromatic fast and tunable incandescent sources - Quantum engineered superradiant emitters The first kind of devices is based on the same geometry as a field effect transistor: the electron gas is excited by a source – drain current, while the electronic density can be controlled by a gate voltage. This point will be also studied in collaboration with STMicroelectronics, which will provide FDSOI and CMOS devices, in order to observe far-infrared optical signals in state-of-the-art electronic devices. In order to fully take advantage of the superradiant character of multisubband plasmons, another generation of devices will also be conceived, realized and characterized, using quantum engineering for resonant excitation. We will design a device based on vertical transport through the electron gas, a plasmon assisted tunnelling device. More selective injection mechanisms will also be investigated, by exploiting the dipole-dipole interaction in systems of tunnel coupled quantum wells.