Two-electron dephasing in a single silicon quantum dot

We study the dephasing of two-electron states in a single silicon quantum dot. Specifically, we consider dephasing due to the electron-phonon coupling and charge noise, treating orbital, valley, and mixed valley-orbit excitations. For phonon-induced dephasing, the intervalley processes are most important and lead to a dephasing rate of about 1 MHz. In an ideal system, dephasing due to charge noise is strongly suppressed due to a vanishing dipole moment. However, introduction of disorder or anharmonicity leads to large effective dipole moments, and hence possibly strong dephasing.