Canalization of developmental processes ensures the reproducibility and robustness of embryogenesis within each species. In its extreme form, found in ascidians, early embryonic cell lineages are invariant between embryos within and between species, despite rapid genomic divergence. To resolve this paradox, we used live light-sheet imaging to quantify individual cell behaviors in digitalized embryos and explore the forces that canalize their development. This quantitative approach revealed that individual cell geometries and cell contacts are strongly constrained, and that these constraints are tightly linked to the control of fate specification by local cell inductions. While in vertebrates ligand concentration usually controls cell inductions, we found that this role is fulfilled in ascidians by the area of contacts between signalingand responding cells. We propose that the duality between geometric and genetic control of inductions contributes to the counterintuitive inverse correlation between geometric and genetic variability during embryogenesis.

Cette thèse traite de la manipulation de l'énergie dans trois systèmes quantiques ouverts différents dans la limite de couplage faible système-environnement, et leurs dynamiques respectives sont décrites par une équation maîtresse quantique markovienne. Dans le premier chapitre, le calcul d'une telle équation est réalisé pour un système particulier, et diverses notions de thermodynamique quantique sont introduites. Pour le premier système physique, on analyse le transport d'énergie le long de chaînes atomiques (entre 2 et 7 atomes) soumises à un rayonnement de corps noir proche de la température ambiante. Il est montré que l'efficacité du transport peut atteindre des valeurs remarquables, surpassant 100% et atteignant jusqu'à 1400% dans certaines configurations. De plus, lorsque l'efficacité est amplifiée, la portée du transport est également considérablement augmentée. Le chapitre suivante traite aussi du transport d'énergie dans des chaînes atomiques. Le système quantique est placé à l'interface d'un isolant topologique photonique (ITP), qui supporte un plasmon polariton de surface (PPS) insensible à la réflexion. Le PPS se propage le long de la chaîne atomique et assiste le transport d'énergie. La comparaison est faite entre PPSs réciproque et unidirectionnel en termes d'efficacité du transport, et il est démontré que ce dernier produit une meilleure efficacité, de plus d'un ordre de grandeur. De surcroît, divers aspects pratiques dus aux propriétés des ITPs sont mis en avant, notamment la robustesse du transport d'énergie en présence de défauts sur le parcours du PPS. Enfin, un système quantique immergé dans un champ électromagnétique hors équilibre thermique est étudié. Il est composé d'un système à trois niveaux d'énergie, jouant le rôle de machine thermique quantique à absorption, ainsi que de N atomes à deux niveaux ("qubits") qui sont affectés par l'action de la machine. Il est montré que la machine est capable de délivrer des tâches thermiques d'intensité significative sur les qubits, y compris lorsque leur nombre augmente. De plus, il est mis en évidence qu'en raison d'interactions qubit-qubit, les tâches réalisées par la machine sont distribuées parmi l'ensemble du système des qubits en interaction, de sorte que dans certains cas, même les qubits complètement découplés de la machine subissent une modification de température considérable. Ce mécanisme de distribution des tâches est analysé à travers les corrélations entre différentes partitions du système quantique. Par ailleurs, le contrôle des tâches thermiques est également discuté.

We will discuss recent results on the theoretical and experimental investigations on solitons in a superfluid Fermi gas along the BCS-BEC crossover. On the theory side, by solving the Bogoliubov de Gennes equations and looking for real and odd solutions for the order parameter, it has been shown that a dark soliton at unitarity posses a large density contrast and fermionic bound states. The superfluid gap is found to be significantly quenched by the presence of the soliton due to the occurrence of Andreev fermionic bound states localized near the nodal plane of the order parameter. By solving the time dependent Bogoliubov de Gennes equations, also the decay and collisions of dark solitons has been investigated. Recently, a cascade of Solitonic Excitations in a Superfluid Fermi gas has been experimentally observed.

Radiative heat transfer between nanostructured objects is a new prolific research line, which open to new heat transfer modulation and amplification possibilities. We will consider the heat transfer between micro/nano-gratings. In particular, we calculate the radiative heat transfer between two identical metallic one-dimensional lamellar gratings [1]. To this aim we present and exploit a modification to the widely-used Fourier modal method, known as adaptive spatial resolution, based on a stretch of the coordinate associated to the periodicity of the grating. We first show that this technique dramatically improves the rate of convergence when calculating the heat flux, allowing to explore smaller separations. We then present a study of heat flux as a function of the grating height, highlighting a remarkable amplification of the exchanged energy, ascribed to the appearance of spoof-plasmon modes, whose behavior is also spectrally investigated. Differently from previous works, our method allows us to explore a range of grating heights extending over several orders of magnitude. By comparing our results to recent studies we find a consistent quantitative disagreement with some previously obtained results going up to 50%. In some cases, this disagreement is explained in terms of an incorrect connection between the reflection operators of the two gratings.

We investigate the transport of energy in a linear chain of two-level quantum emitters ("atoms")weakly coupled to a blackbody radiation bath [1]. We show that, simply by displacing one ormore atoms from their regular-chain positions, the efficiency of the energy transport can beconsiderably amplified of at least one order of magnitude. Besides, in configurations providingan efficiency greater than 100% , the distance between the two last atoms of the chain canbe up to 20 times larger than the one in the regular chain, thus achieving a much longer-rangeenergy transport. By performing both a stationary and time-dependent analysis, we ascribethis effect to an elementary block of three atoms, playing the role of excitation injector fromthe blackbody bath to the extraction site. By considering chains with up to 7 atoms, we alsoshow that the amplification is robust and can be further enhanced up to 1400%.-------------------------[1] P. Doyeux, R. Messina, B. Leggio, and M. Antezza, Phys. Rev. A 95, 012138 (2017).

We investigate spontaneous and pumped entanglement of two level systems in the vicinity of a photonic topological insulator interface, which supports a nonreciprocal (unidirectional), scattering-immune and topologically-protected surface plasmon polariton in the bandgap of the bulk material [1]. To this end, we derive a master equation for qubit interactions in a general three-dimensional, nonreciprocal, inhomogeneous and lossy environment. The environment is represented exactly, via the photonic Green function. The resulting entanglement is shown to be extremely robust to defects occurring in the material system, such that strong entanglement is maintained even if the interface exhibits electrically-large and geometrically sharp discontinuities. Alternatively, depending on the initial excitation state, using a non-reciprocal environment allows two qubits to remain unentangled even for very close spacing. The topological nature of the material is manifest in the insensitivity of the entanglement to variations in the material parameters that preserve the gap Chern number. Our formulation and results should be useful for both fundamental investigations of quantum dynamics in nonreciprocal environments, and technological applications related to entanglement in two-level systems.