![]() ![]() Coherent evolution between the states that have a relatively small energy splitting of 20 μeV is excited by a fast electrical pulse, and the results are projected as the occupations of two different charge states for read-out by a nearby charge-sensing channel. Here, we report the coherent manipulation of a qubit based on the two valley states of an electron confined in a silicon quantum dot. Thus, characterization and control of valley states is important in order to develop a scalable quantum-computing architecture using silicon-based QDs. The valley states often affect both the encoding and the read-out of qubits 1. They are nondegenerate with a splitting energy that depends on the microscopic details of the interface 6, 7, 8, 9. Only the two low-energy valley states are energetically relevant to charge/spin states in QDs. Electrons in bulk silicon have six degenerate states, known as valley states, which, when confined to two dimensions, separate into four high-energy states with higher effective mass and two lower energy states. However, the characterization and control of the valley degree of freedom in silicon nanostructures presents a major challenge. During the last several years, coherent control of spin-based qubits in Si QDs has been successfully demonstrated by a number of groups 2, 3, 4, 5. Gate-defined quantum dots (QDs) in silicon heterostructures are emerging as a leading candidate for the physical implementation of quantum computing in the solid state, mainly due to the long coherence times of the individual spins in silicon and the potentials for scaling and integration with mainstream classical electronics 1. ![]()
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