Full quantum control of enantiomer-selective state transfer in chiral molecules
despite degeneracy
Abstract
The driven quantum asymmetric top is an important paradigm in molecular
physics with applications ranging from quantum information to chiral-sensitive
spectroscopy. A key prerequisite for these applications is the ability to completely
control the rotational dynamics. The inherent degeneracy of quantum rotors
poses a challenge for quantum control since selecting a particular rotational
state cannot be achieved by spectral selection alone. Here, we prove complete
controllability for rotational states of an asymmetric top belonging to degenerate
values of the orientational quantum number M. Based on this insight, we
construct a pulse sequence that energetically separates population in
degenerate M-states. Introducing the concept of enantio-selective controllability,
we determine the conditions for complete enantiomer-specific population transfer
in chiral molecules and construct pulse sequences for the example of
propanediol and carvone molecules for population initially distributed over
degenerate M-states. Our work shows how to leverage controllability analysis for
the solution of practical quantum control problems.