University of Basel

One of the remarkable features of the mammalian brain is its capability to learn. This is particularly evident during infancy, when novel context is rapidly integrated and transformed into new memory. How early-life experiences are encoded in the developing hippocampus, a brain region central to the formation and recall of memory, has not been well understood. We know very little how neural populations in the hippocampus are activated during learning, allowing for both a generalised yet flexible encoding of information. Recent work suggests that a subset of hippocampal neurons show more rigid, stable activation patterns across the behavioural domain while others are more plastic. How their properties emerge during infancy and evolve during brain maturation is the centre of this proposal. To answer these questions, I propose to study the ensemble code in the developing mouse hippocampus. I will use a combination of calcium imaging, viral labelling, and chemogenetic techniques paired with a behavioural navigation assay to measure in vivo the activities of 100s of neurons while the animal explores known and novel environments. Specifically, it is my ambition to understand how the functional properties of rigid and plastic neurons in CA3 region emerge during development and to identify the neural circuitry encoding episodic memories in the infant and adult brain. By bridging developmental, systems, and behavioural neuroscience, the proposed research will provide highly novel contribution to our understanding of learning during brain maturation.

An efficient nonlinear quantum gate between two single-photons is highly desirable, as it will enable processing quantum information stored in optical photons. This capability is essential for building next generation of quantum networks, and optical quantum computing. However, such a device is constrained by lack of interaction between optical photons in natural environments. Interestingly, cavity quantum electrodynamics provides several paths towards achieving nonlinear interaction between photons. This action aims at realizing a high fidelity and efficient nonlinear gate between two single-photons using a compact solid-state design. Our approach is based on using the spin-state of a hole in an InAs/GaAs quantum dot to mediate the interaction between the photons. It has recently been demonstrated that the quantum coherence of the hole state can be on the order of several hundreds of nanoseconds. Also, the hole-states have been shown to have very coherent optical transitions which makes them an ideal candidate to realize spin-photon interfaces. In order to boost the interaction between the photons and the quantum dot, a novel microcavity structure will be used. The microcavity structure has recently been developed in the host group and shows spectacular features such as a Q-factor of 1 million, and a cooperativity of 100, making the combination of the hole-state and the microcavity structure an ideal platform to realize photonic gates. The results of this action will be highly instrumental for building quantum repeaters, and may open new directions for quantum computers based on optical photons. For instance, such a nonlinear gate may be combined with a linear network of coupled waveguides to enhance the simulation capabilities of the linear network. Finally, this action is aligned very well with the goals of the Quantum Technologies flagship initiative, and will contribute to the collective effort by the European researchers towards a lead in quantum technologies.