Complete Controllability Despite Degeneracy:
Quantum Control of Enantiomer-Specific State Transfer
in Chiral Molecules.
Abstract
We prove complete controllability for rotational states
of an asymmetric top molecule belonging to degenerate values
of the orientational quantum number M. Based on this insight,
we construct a pulse sequence that energetically separates
population initially distributed over degenerate M-states,
as a precursor for orientational purification. Introducing
the concept of enantio-selective controllability,
we determine the conditions for complete enantiomer-specific
population transfer in chiral molecules and construct pulse
sequences realizing this transfer for population initially
distributed over degenerate M-states. This degeneracy presently
limits enantiomer-selectivity for any initial state except the
rotational ground state. Our work thus shows how to overcome an
important obstacle towards separating, with electric fields only,
left-handed from right-handed molecules in a racemic mixture.