# Magnetic pulses enable multidimensional optical spectroscopy of dark states

## TL;DR

This paper introduces a novel magnetic pulse technique combined with multidimensional optical spectroscopy to access and study dark quantum states with low dipole moments, which are otherwise difficult to detect.

## Contribution

It proposes a new three-pulse spectroscopic scheme using magnetic pulses to control spin precession and reveal dark states in quantum systems.

## Key findings

- Magnetic pulses can induce transitions between bright and dark spin states.
- Dark states become accessible to standard spectroscopy through this method.
- The approach enables detailed study of low dipole moment quantum states.

## Abstract

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.