Process tomography of coherent state transfer from light polarization to electron spin polarization in a semiconductor

We performed process tomography of a coherent state transfer from light polarization into electron spin polarization in a semiconductor quantum well. The density matrix of the generated electron spin state was reconstructed by a three-dimensional tomographic Kerr rotation measurement so that we could quantitatively evaluate the transfer process. We found that the process fidelity of the state transfer was 81% and clarified that the phase-flip error caused by mixing with another Zeeman sublevel at the hole state was the major contributor to fidelity degradation.