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 $|1〉\leftrightarrow |2〉\leftrightarrow |3〉\leftrightarrow |1〉$, 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.

• Received 19 April 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.183002