  In Si quantum dots, valley degree of freedom, in particular the generally
small valley splitting and the dot-dependent valley-orbit phase, adds
complexities to the low-energy electron dynamics and the associated spin qubit
manipulation. Here we propose a four-level model to extract tunnel coupling
information for a Si double quantum dot (DQD). This scheme is based on a charge
sensing measurement on the ground state as proposed in the widely used protocol
for a GaAs double dot [DiCarlo et. al., PRL 92. 226801]. Our theory can help
determine both intra- and inter-valley tunnel coupling with high accuracy, and
is robust against system parameters such as valley splittings in the individual
quantum dots.
