The major front of our research is on spin qubit decoherence, and we have mostly focused on decoherence of multiple qubits or non-equilibrium spin qubits. Specifically, we have completed our studies of two- and three-spin decoherence due to hyperfine interaction. We have investigated spin relaxation due to charge noise and/or spin valley mixing, and found that charge noise and spin-valley mixing could both be an important ingredient to spin relaxation at relatively low magnetic fields. We have studied decoherence of a driven qubit, and found that the electron relaxation and dephasing properties are strongly modified by the presence of driving. We have studied the scaling behavior of decoherence for a multiple-spin-qubit system under the influence of hyperfine interaction, and found that the multi-qubit decoherence properties are reasonably favorable. Lastly, we have investigated relaxation of a moving spin qubit, and found that phonon bottleneck effect reduces spin relaxation for larger magnetic fields, and fast motion can reduce spin relaxation for a wide range of magnetic fields. We have studied dynamics and relaxation of the spin of a tunneling electron, and found regimes where spin relaxation is minimized and spin hotspot is eliminated.
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