Seminar: Klaus Mølmer

Scalable designs for quantum information processing make use of flying qubits, i.e., photon or phonon wave packets that can communicate quantum states and gate operations between remote material (stationary) qubits in a larger network. While a precise description of how a travelling pulse of quantum radiation interacts with a local material quantum system is a crucial theory component in quantum optics and quantum information technologies, our textbooks do not provide a formal description of this elementary interaction process. 

I shall discuss why and how a theory for such processes must fundamentally differ from the way textbooks describe the interaction between, e.g., atoms and discrete cavity modes. I shall then cast the problem in a form that permits a (simple) density matrix theory for the radiation restricted to any choice of a single or a few wave packet modes. I shall show multiple applications of the theory of relevance to recent experiments with atomic and superconducting qubits interacting with pulses of optical, microwave and acoustic radiation.