While performing its function in cells, DNA is subject to a considerable amount of mechanical deformations due to the interactions with other bio-molecules and to thermal fluctuations. To understand the functioning and properties of DNA, it is important to understand its mechanics, a task which involves modeling and experiments. In this talk I will give a general overview of our present understanding of DNA physical properties and of DNA-protein interactions, highlighting some recent results and future challenges.

Systems driven out of thermal equilibrium can form spontaneously complex structured spatial and spatio-temporal states via self-organization, even if the drive is homogeneous in space and constant in time. Broad-area vertical-cavity surface-emitting lasers (VCSELs) emerged as a highly controllable and versatile tool to investigate this interesting nonlinear laser dynamics as they are semiconductor lasers with very short (about 1 µm) but broad (about 200 µm diameter) microcavities. The high circular symmetry of VCSELs also allows for the polarization degrees of freedom to be self-organized. I will present investigations on the spontaneous appearance of vector vortex beams in a VCSEL with frequency-selective feedback with a radial, spiral and hyperbolic polarization structure and their interpretation as high order vectorial solitons. Vector vortex beams are an example of “fully structured light”, i.e. light beams with spatially inhomogeneous intensity and polarization distribution, usually created by specialized linear beam shaping devices. I will also review some results on mode-locking of laser cavity solitons, i.e. the possibility of spontaneous pulsations due to operating on multiple longitudinal modes. This might pave a path to “light bullets”, i.e. light self-localized in all three dimensions. Evidence of spin memory for spin polarized pumping in the photoluminescence of quantum dot vertical-gain structures is presented. This opens the path to vertical-external cavity lasers with polarization control via pumping (“spin-VECSELs”).

Cosmography is the science that maps and measure the large-scale structures in the observed Universe that are built from the tug of war between gravitation and space expansion. We use the direct galaxy distances to compute the 3-dimensional peculiar/gravitational velocity field in order to reconstruct the underlying distribution of mass responsible of these motions. Filaments, walls and voids are embedded into a more global view of large gravitational watersheds delineated by empty regions. The main advantage of mapping superclusters as watershed basins is the robustness of the definition, allowing them to be used as cosmological probes. The seminar will be a journey relating the telescope campaigns, the discovery of our home supercluster « Laniakea » and the 5 newly cartographied neighbors. We will expose measurements of parameters linked to the cosmology principle of homogeneity and the gravitation law, and inform about the upcoming large surveys.

Individual bacteria transported in viscous flows, show complex interactions with flows and bounding surfaces resulting from their complex shape as well as their activity. Understanding these transport dynamics is crucial, as they impact soil contamination, transport in biological conducts or catheters, and constitute thus a serious health thread. Here we investigate the trajectories of individual E-coli bacteria in confined geometries under flow, using microfluidic model systems in bulk flows as well as close to surfaces using a novel Langrangian 3D tracking method. Combining experimental observations and modeling we elucidate the origin of upstream swimming, lateral drift or persistent transport along corners.

The quest for efficient spin-photon interfaces is at the core of many proposals in quantum optics. On the one hand, it would allow developing deterministic spin-photon and photon-photon gates for quantum computing, as well as multi-entangled states with N photons, for quantum communications. On the other hand, it would allow implementing interesting fundamental studies on quantum measurement, whereby each photon can be used to « observe » the spin system. In this seminar, I will briefly review some systems used for spin-photon coupling, and then focus on the recent progress made in C2N, using charged quantum dots in pillar-based cavities. I will show how we can use the same device as a quantum emitter – to emit several photons all entangled with the same spin, or as a quantum receiver – to allow exchanging the quantum information between a confined spin and the incoming photons. Along the way, I will show how one can play with the polarization degree of freedom in various ways, to encode multi-photon entanglement as well as to extract information on the various processes occurring in our solid-state structures. Finally, I will discuss some perspectives of our work, for the realization of optimized spin-photon interfaces and their use in various applications.

It is by now commonplace to claim that biology is ‘self assembled soft matter’. That claim is true, but misses half of the physics. Along side self assembly, biology from molecules through cells to ecosystems, also makes use of highly targeted self disassembly processes (‘death’) to produce products to feed back into self assembly. Very often, these disassembly processes are active, typically consuming energy in the form of ATP. In this talk, I will give an overview of biological active self disassembly processes, and argue that coming to a physics-based understanding of such process would represent not only a big step forward in biological physics, but should offer a new paradigm for the synthesis of new materials by deliberately coupling self assembly to targeted active self disassembly.