Quantum mechanics is a theory of isolated sub-systems. Once a quantum system is coupled to an external environment, quantum coherence and correlations are eventually reduced to classical statistics. The study of open quantum systems can therefore shed light on the quantum to classical transition.
  In this talk I will describe recent experiments at the Weizmann Institute in which a single trapped ion, a highly coherent quantum system, is coupled to a continuum of electromagnetic vacuum modes via spontaneous scattering of laser photons. Several aspects of open quantum system dynamics are studied with this system. We show how the ion-photon entanglement leads to decoherence of ion quantum states. We further show that this entanglement can be used to reverse photon scattering errors. Finally we show how, through the coupling of the ion to the electromagnetic vacuum, a natural measurement eigen-basis is self-selected.