Decoherence of many-spin systems in NMR: From molecular characterization to an environmentally induced quantum dynamical phase transition

GONZALO A. ÁLVAREZ

arXiv:0705.2350 - Tesis Doctoral

Año: 2007 p. 1 - 147

The control of open quantum systems has a fundamental relevance for elds rangingfrom quantum information processing to nanotechnology. Typically, the systemwhose coherent dynamics one wants to manipulate, interacts with an environment thatsmoothly degrades its quantum dynamics. Thus, a precise understanding of the innermechanisms of this process, called \decoherence", is critical to develop strategies tocontrol the quantum dynamics.In this thesis we solved the generalized Liouville-von Neumann quantum master equationto obtain the dynamics of many-spin systems interacting with a spin bath. We alsosolve the spin dynamics within the Keldysh formalism. Both methods lead to identicalsolutions and together gave us the possibility to obtain numerous physical predictionsthat contrast well with Nuclear Magnetic Resonance experiments. We applied thesetools for molecular characterizations, development of new numerical methodologies andthe control of quantum dynamics in experimental implementations. But, more important,these results contributed to fundamental physical interpretations of how quantumdynamics behaves in open systems. In particular, we found a manifestation of an environmentallyinduced quantum dynamical phase transition.