Jörg Wrachtrup

Title

Seeing the quantum world in a grain of carbon

Abstract

William Blake’s „To see the world in a grain of sand“ has become a synonym for looking into fundamental physical problems in simplified model systems. Quite remarkably, solid state systems - and among them diamond defects and rare earth dopants - have developed into such models. Both types of dopants’ ions are atomic sized impurities which retain much of their atomic properties when deposited inside the solid. Low spin-orbit and spin-phonon interaction guarantee almost complete isolation of spin states from elementary excitations in the surrounding host material. As a result, single or small clusters of such impurities can be used to study quantum correlations, entanglement generation, its sudden death, as well as efficient shelving of complete quantum states. The impurity atoms usually are very sensitive probes for their environment, e.g. nuclear spins in their vicinity. Indeed it turns out that the unitary evolution of the impurities’ spin, coupled to a handful of nuclear spins, models the sole spin-bath interaction, providing an intriguing example for the relation between quantum and classical description. Hence, they also serve as models for the thermodynamic properties of mesoscopic sized quantum systems.