Seminário de Computação e Informação Quântica 

23/05/2013, 15:00 — 16:00 — Sala P3.10, Pavilhão de Matemática
Klaas Bergmann, Technical University Kaiserslautern

Population transfer between quantum states to perfection: Stimulated Raman Adiabatic Passage (STIRAP)

In many areas of science (e.g. physics, chemistry, quantum information) controlled modification and in particular efficient transfer of population between quantum states is wanted. Many schemes are known that allow varying the usually thermal population distribution. Of particular interest are means for selective and efficient transfer of population from quantum state \(i\) to quantum state \(f\). “Efficient” means that nearly 100% of the population residing initially in state \(i\) reaches state \(f\). This also implies high selectivity as no other quantum state receives population. Traditional techniques such as Raman scattering, optical pumping or stimulated emission pumping fail to reach the goal. Spontaneous emission, which channels population into other levels,is a main problem. STIRAP solves that problem through a surprisingly simple, but at first glance very puzzling, sequence of radiative interactions: The quantum system is first exposed to the radiation field which connects the final state with an intermediate state (thus, it does not couple to the quantum state which carries initially the population) before the second radiation field couples the initial state to the same intermediate one. The basic phenomena and the physics building blocks of this process, the concept of which is now applied in very many areas, are presented and explained.