Séminaire de l'IQ: Clément Godfrin

Clément Godfrin Institut Louis Néel Genoble Titre: Playing with a single 3/2 nuclear spin Résumé: More than a hundred years ago, while quantum theory had just been born, physicists used thought experiments. These reasonings allowed them to debate the controversial point of the theory while undoing the experimental constraints. Since then, many advances in experimental techniques (low temperature, nano-fabrication, electronics...) offer physicists the opportunity to study systems worthy of those imagined by the founders of the quantum theory. During my presentation, I propose to play with one of these toy model systems, namely a single 3/2 nuclear spin. We will first see how we can measure an object which is highly isolated from its environment using a single molecular magnet transistor [1]. Then we will couple the nuclear spin to a microwave electric field [2] and measure the coherent manipulation of the 3 nuclear spin transitions, thus demonstrating that we have a fully controlled 4-level quantum system, a qudit. With their state space of dimension d>2, Qudits open fascinating experimental prospects. Indeed, they offers the opportunity to explore issues of quantum contextuality, expressions of geometric phases, facets of quantum entanglement and many other foundational aspects of the quantum world. In this presentation I will propose and implement protocols based on a generalization of the Ramsey interferometry to a multi-level system to measure among others the accumulation of geometric phases and of quantum gate phase. Finally we will see multi- level resonance dynamic which are the signature of the implemention of the Grover quantum algorithm [3]. As an outlook, I will display how to apply these experiments on a single nuclear spin of a silicon based sample and show how we could apply a quantum error correction protocol on this single qudit system [4]. [1] Godfrin C. et al. ACS Nano 11, 3984 (2017) [2] Thiele S. et al. Science 344, 1135 (2014) [3] Godfrin C. et al. Phys. Rev. Lett. 119, 187702 (2017) [4] Pirandola S. et al. Phys. Rev. A 77, 032309 (2008)"