| This dissertation aims to clarify the dynamics of encoded spin qubits in semiconductor quantum dots. The major part of the dissertation features a study of pure dephasing of multiple-electron spin states in coupled semiconductor quantum dots due to hyperfine interaction. With a perturbation approach, this work can effectively describe the multiple-electron spin states, and calculates the dynamics of qubit free evolution and with the application of dynamical decoupling within reasonable approximation. The derived hyperfine induced dephasing can offer an understanding of the decoherence of a pseudospin qubit, and is also relevant to the fidelity of gate operations.;The remaining part of the dissertation presents the relaxation dynamics of spin-orbit-hybrized states in a nanowire quantum dot due to electrical noises. To deal with strong spin-orbit coupling, the employed treatment starts by solving the Schrodinger equation for a spinor, and the author wishes to develop a convenient and effective tool to describe the spin-orbit-hybrized states. |
