Physical Review Letters
Cyclic Population Transfer in Quantum Systems with Broken Symmetry
Petr Král, Moshe Shapiro
Abstract
We show that quantum systems with broken symmetry can be selectively excited due to the coexistence of one- and two-photon transitions between the same states. Discrimination between two mirror-symmetric quantum wells or left- and right-handed chiral molecules can be accomplished by a ``cyclic population transfer'' process, in which one optically couples three system states $|1〉\ensuremath{\leftrightarrow}|2〉\ensuremath{\leftrightarrow}|3〉\ensuremath{\leftrightarrow}|1〉$, and completely transfers population from state $|1〉$ to state $|2〉$ and $|3{〉}_{M}$ (i.e., state $|3〉$ of the mirror imaged system) or state $|3〉$ and $|2{〉}_{M}$, depending on the laser phases.