Jonas Ola Oscar Larson Universitetslektor

I nuläget undervisar jag kursen Analytisk mekanik (FK7049) som ges varje vår på fysikum, främst för masterstudenter. Kursen täcker standardmatierialet för motsvarande kurs, se https://link.springer.com/book/10.1007/978-3-030-34882-3

Jag är dessutom lärare på Kollokviumkursen for doktorander samt sitter med i kommitén som utvärderar alla bacheloruppsatser.

• Quantum optics - light matter interaction Quantum optics is a field studying how light and matter interact when both subsystems are treated quantum mechanically. One strategy to experimentally reach the regimes where a full quantum description is essential is to use atoms confined within high-quality optical resonators. It is here possible to single out single atomic electronic transitions as well as single photon cavity modes. These systems are well described by various types of Jaynes-Cummings-like models. In modern times the atoms can be replaced by superconducting devices and the resonators by "transmission line resonators", such that everything can be contained on electronic chips. These are typically what is employed by Google and others in order to build early versions of quantum comupters. I have approached these systems in somewhat unconeventional views, like thinking of them in terms simple "molecules" where the photon degrees-of-freedom are serving as vibrational phonons of a molecule. Recently I am also describing these models as exotic lattice models with interesting topological properties.
• Quantum phase transitions and quantum simulators Traditionally, a continous phase transition is accompamied by a spontaneous symmetry breaking; in the normal phase the state is symmetric with a vanishing order parameter, while in the symmetry broken phase it has a non-zero order parameter that specifies the broken symmetry. The presence of such phase transitions in the clssical world are due to thermal fluctuations that cause the state to spontaneously pick a "direction". Quantum systems possess inherent fluctuations thanks to the Heisenberg uncertainty principle, and it turns out that these can also cause spontaneous symmetry breaking - quantum phase transitions. A relatively new field is to study well known quantum many-body models in the realm of highly controllable experimentally relevant systems. These are tailored quantum systems that serve the purpose of simulating another system that is difficult to access experientally - a quantum simulator. In a way it is type of a quantum comuter, however not a universal one. Quantum simulators are often considered when studying quantum critical models (phase transitions), for example to map out the phase diagram of some interesting Hamiltonian. We consider different realizations of quantum simulators, but one particularly important one is formed from ultracold atoms held in optical lattices. These are very robust, clean and versatile systems, ideal for realizing quantum simulators.
• Open quantum systems Quantum physics provides many advantages over classical physics, i.e. entanglement and superpositions. However, it comes with a high prize; these properties are extremely fragile for and imperfections. The greatest difficulty being the coupling of the system to its surrounding environment. This invitebly leads to decoherence and the loss of ''quantumness''. To describe the effects of an environment one must give up unitary time-evolution, and work with mixed states. We try to build a deeper understaing for the novel physics emerging from such non-unitary evolution, and what new phases of matter that may exist.