**Abstract:**

One of the grand challenges in science and technology today is to build a quantum computer that can perform computation tasks that are unsolvable by classical computers. Semiconductor quantum dots are a leading approach for the implementation of solid-state based quantum computing, as the coherence time of the qubits can be extremely long and various interactions, inherent to semiconductors, can be harvested to precisely control superposition and entanglement. In this talk, I will describe world-wide experimental activities to use charge and spin degree of freedom of individual electrons to encode and process quantum information. I will also present our recent results at UCLA to coherent manipulate and to perform projective measurements of the valley states of individual electrons, as valley states represents another quantum degree of freedom, complementary to that of charge and spin.