Living organisms use dynbamic, isothermal processes like self-organization to function and evolve. Imitating these processes with synthetic soft matter can lead to innovative and bio-inspired materials. DNA nanotechnology offers programmability and versatility for creating desired 2D and 3D nanostructures. Although reconfigurability of DNA nanostructures is possible, building growing and evolving structures is still challenging. Our recent work in Damien Baigl’s team demonstrated that using an adjusted salted buffer allows DNA strands to self-assemble into programmed and reconfigurable morphologies at room temperature [1]. In this seminar, I will discuss how we can go further self-assemble DNA nanostructures at 37°C in bio-relevant buffers, and notably in the presence of cells. I will also show that the method enabled us to induce the living growth of DNA nanotubes, either in bulk solution or inside biomimetic micro-compartments. Finally, I will present the self-organization of nanotubes with electrostatic interactions, resulting into large DNA superstructures that exhibit reversible dynamics triggered by external stimuli. All these results open up perspectives for the development of dynamic and evolving architectures inside living and/or temperature-sensitive environments. 1. Rossi-Gendron, C.; El Fakih, F.; Bourdon, L.; Nakazawa, K.; Finkel, J.; Triomphe, N.; Chocron, L.; Endo, M.; Sugiyama, H.; Bellot, G.; et al. Isothermal Self-Assembly of Multicomponent and Evolutive DNA Nanostructures. Nat. Nanotechnol. 2023, doi:LF.LF38/s41565-023-01468-2.

In theories with compact dimensions, Bubbles of Nothing (BoN) are vacuum decays in which the compactification manifold C shrinks to a point, with the instability expanding at the speed of light and leaving nothing (not even spacetime) behind. The Swampland Cobordism Conjecture predicts spacetime-ending configurations (known as bordisms to nothing) such as these being commonplace in a consistent theory of Quantum Gravity. Most constructions of BoN or more general bordisms to nothing found in the literature feature simple instances of C or singular bordisms, which cannot be approached from the effective field theory. Assuming the solution mediating such decay to nothing is homeomorphic to a smooth description, one can go a step further, and obtain topological properties from those of C. Through the use of Morse-Bott theory, these can be translated into information on the number and types of topology changes the compact manifold experiences as we move towards the tip of the bordism, as well as the location of possible cobordism defects. I will illustrate these results with different examples coming from String Theory and, time permitting, study more complicated arrangements such as BoN collisions. The talk is based on the paper https://arxiv.org/abs/24LF.2CR72.

Controlling and detecting individual spins in solids is interesting for high-resolution magnetic resonance spectroscopy and quantum computing. I will present a new set of methods that we have recently developed to do so, at millikelvin temperatures. The key idea is to count the microwave photons that an electron spin emits after excitation, in complete analogy with optical fluorescence [1]. The spin radiative rate is enhanced via the spin Purcell effect, by coupling the spins to an on-chip planar superconducting microwave resonator [2]. Microwave photon counting is performed using a detector that we have developed and which is based on a superconducting transmon qubit [3]. We detect individual Er3+ spins in a CaWO4 crystal [4]. Using an electron spin, we sense individual 183W nuclear spins. We achieve nuclear spin readout, polarization, and coherent control [5]. The nuclear spins have seconds-long coherence times. We also develop new control methods based on stimulated Raman microwave drives. Using an Er3+ spin strongly coupled to two 183W spins, we demonstrate a two-nuclear-spin-qubit gate, and generate an entangled state with second-long lifetime [6]. [1] Albertinale et al., Nature 600, 434 (2021) [2] Bienfait et al., Nature 531, 74 (2016) [3] Balembois et al., PRApplied 21, 014043 (2024) [4] Wang et al., Nature 619, 276 (2023) [5] Travesedo et al., arXiv:2408.14282 [6] O'Sullivan et al., arxiv:24LF.LF432