We introduce a novel method to find exact density operators for a spin-1/2 particle in time-dependent magnetic fields by using the one-mode bosonic representation of su(2) and the connection with a time-dependent oscillator. As illustrative examples, we apply the method to find the density operators for constant and/or oscillating magnetic fields, which turn out to be time-dependent in general.
Cite
@article{arxiv.quant-ph/0511241,
title = {Method for Solving the Bloch Equation from the Connection with Time-Dependent Oscillator},
author = {Sang Pyo Kim},
journal= {arXiv preprint arXiv:quant-ph/0511241},
year = {2007}
}