ABSTRACT

Scalable architectures for quantum computing such as solid-state qubits are necessary to perform useful computations. Research on Si qubits has accelerated the demonstration of 2-qubit logic gates with enhanced coherence time using isotopically purified substrates. The main unresolved issue is the large-scale integration of qubits. The advantage of Si-based systems is that they can employ complementary metal-oxide semiconductor process technologies for large-scale integration. The chapter describes the fabrication and electrical properties of physically defined coupled quantum dots prepared on silicon-on-insulator substrates, which are promising for high-density integration. A singlet-triplet qubit in a double quantum dot based on Si/SiGe heterostructures has been demonstrated. The conduction band structure of Si is more complex than that of GaAs because electrons in the conduction band of silicon have valley degrees of freedom. In recent years, valley physics in silicon has been studied both experimentally and theoretically.