All-optical control of pendular qubit states with nonresonant two-color laser pulses

Practical methodologies for qubit controls are established by two prerequisites, i.e., preparation of a well-defined initial quantum state and coherent control of that quantum state. Here we propose a quantum control method, realized by irradiating nonresonant nanosecond two-color ( ω and 2 ω ) laser pulses to molecules in the pendular (field-dressed) ground state. The two-color field nonadiabatically splits the initial pendular ground state |0̃,0̃⟩ to a superposition state of |0̃,0̃⟩ and |1̃,0̃⟩ , whose relative probability amplitudes can be controlled by the peak intensity of one wavelength component ( ω ) while the peak intensity of the other component (2 ω ) is fixed. The splitting of the quantum paths is evidenced by observing degrees of orientation of ground-state-selected OCS molecules by the velocity map imaging technique. This quantum control method is highly advantageous because any polar molecule can be controlled regardless of the molecular energy structures.