  The study and manipulation of low dipole moment quantum states has been
challenging due to their inaccessibility by conventional spectroscopic
techniques. Controlling the spin in such states requires unfeasible strong
magnetic fields to overcome typical decoherence rates. However, the advent of
terahertz technology and its application to magnetic pulses opens up a new
scenario. In this article, we focus on an electron-hole pair model to
demonstrate that it is possible to control the precession of the spins and to
modify the transition rates to different spin states. Enhancing transitions
from a bright state to a dark state with different spin means that the latter
can be revealed by ordinary spectroscopy. We propose a modification of the
standard two-dimensional spectroscopic scheme in which a three pulse sequence
is encased in a magnetic pulse. Its role is to drive transitions between a
bright and a dark spin state, making the latter susceptible to spectroscopic
investigation.

Quantum Physics;Materials Science;Chemical Physics