Identifying the material time in physical aging by Jeppe Dyre, followed by Self-assembly of active amphiphilic Janus particles by Chantal Valeriani

In this talk I will mainly present a series of experimental results regarding the dynamics of passive particles in liquid bath of active ones. The active particles act here, via the flows they generate, as localized and erratic sources of momentum for the passive beads leading to non-trivial dynamics. Beyond their exciting features for the physicist, active/passive systems are worth studying quantitatively for applications as diverse as the transport of passive entities in cells, biogenic mixing (i.e. mixing of the ocean by living creatures), virus infection, cargo transport (e.g. drug delivery) or self-assembly (e.g. via motility-induced phase separation). The model system I consider is composed of the motile micro-alga Chlamydomonas reinhardtii, a model organism at numerous levels, and polystyrene beads. I will first present results about the diffusive dynamics of micron-size spheres in homogeneous suspensions of algae. I will then show how the coarse-grained dynamics is related to the near-field hydrodynamics of the swimming organism. Finally I will talk about recent results regarding systems of large colloids in spatially heterogeneous suspensions of algae and show how our findings could be (perhaps) put at stake to actually perform useful tasks.

In my previous research works, I studied with molecular modeling various materials, porous or not, either porous clays or silica surfaces, porous electrodes of supercapacitors and carbon or boron nitride nanotubes. For all the projects, one leitmotif has always been to work with experimentalists or compare the results to experimental data ; for example, electrochemical experiments for supercapacitors, or infrared spectroscopy for adsorption on silicas. Depending on the problematics, the materials were studied at multiple scales, either by quantum chemistry, Monte Carlo or molecular or brownian dynamics. I will present some key results, pointing out the dynamics of molecules in porous media and the adsorption at the quantum scale.

Light-matter interactions lie at the heart of a very broad range of fundamental physics and applications. At a single particle level, such interactions enable all-optical quantum control of qubits which is of great interest for quantum information. At a more macroscopic level, these interactions are a key to collective phenomena such as condensation of exciton-polaritons in microcavities. In this talk I will present my previous and current research which is unified under the broad field of light-matter interactions in semiconductors. In particular, I will briefly introduce polariton condensates along with the typical experimental methods used for their study and will cover a few exciting experiments ranging from the observation of pinned singly-charged vortices to the demonstration of a polaritonic Josephson junction. Moving from such collective quasi-particle phenomena to the investigation of more discreet quantum emitter systems, I will then address experimental efforts on the coherent control of scalable quantum emitter platforms. More specifically, I will present recent work on site-controlled quantum dots and silicon vacancies in diamond, and will conclude with an overview of my vision for future research.

The ubiquity of collective motions observed at all scales in biological systems has driven a surge of scientific activity. Within physics, important theoretical progress was achieved by studying microscopic point-particles models and their continuous descriptions. Among the landmark results are the possibility of a true long-range polar ordered collective motion as well as of a Motility Induced Phase Separation (MIPS). The robustness of these observations against the numerous factors integrated out in the above effective models is a matter of crucial importance.

This is where human-designed model experimental systems have a key role to play. Janus colloids, swimming droplets or walking grains are amazing experimental realization of self propelled particles. They are far more simple than their biological inspiration, and already contain important realistic factors, such as hydrodynamics effects and pairwise force interactions, which, at least in principle, can be controlled.

In the present talk, I will illustrate that matter in the case of two remarkable experimental systems, namely rolling colloids and walking grains.

Colour centres in diamond, in particular the nitrogen-vacancy centre, have recently attracted significant attention as versatile tools for quantum information processing, magnetometry and biolabelling, most of these applications relying on the long-lived electronic spin of the nitrogen-vacancy centre. However, for quantum information processing, this centre suffers from mediocre optical properties which limit its use in the absence of photonic structures. In contrast, the silicon-vacancy centre displays remarkable optical properties but so far, its spin degree of freedom had remained elusive.

Using resonance fluorescence, we have shown that the silicon-vacancy centre possesses an optically accessible spin S=1/2. We have then probed the coherence of this spin through coherent population trapping, thus demonstrating the possibility to control the spin with light. Finally, we have achieved coherent control of the spin, thereby showing that the silicon-vacancy centre is a promising spin-photon interface in a quantum network.

Cas nucleases are enzymes that can be programmed with guide RNA to cut DNA with a complementary sequence. This programmability has made Cas nucleases popular genome editing tools, as they can be directed towards any desired genomic sequence by synthetically produced guide RNA. Due to the large number of competing off-targets in a genome, DNA is also cleaved at sequences with only a partial match to the guide. Such off-targeting poses a significant problem for any therapeutic application, and a large number of experiments have been performed to establish a rather peculiar set of empirical targeting rules. These empirical rules are as of yet unexplained, and detail the effect of mismatches at various positions and at various relative distances. We construct a kinetic model that explains the empirical targeting rules, and argue that it can be used to improve on current bioinformatic approaches used to predict off-target locations for genome editing applications.

It is well established that quantum dots (QD) present an atom-like spectrum and constitute a very good indistinguishable and single photon emitter making them promising candidates for quantum information processes. In this talk I will show how their discrete energy structure allows to probe the interactions between a quantum system and its surrounding solid-state environment (fluctuating charges, phonons). By performing two-photon interference experiments in an Hong-Ou-Mandel setup under strictly resonant excitation and as function of the temperature, the QD-phonon interaction can be probed. We have identified two different processes responsible for the loss of the indistiguishability, one because of real phonon transitions, the other one accounts for virtual phonon transitions due to the presence of higher lying excited states in the QD.