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Charge sensing spectroscopy in Si/SiGe quantum dot qubits

Electron spins confined in quantum dots are promising candidates for solid-state qubits. Due to negligible spin-orbit coupling, electron spins in silicon quantum dots have been predicted to have extremely long coherence times, a large advantage for spin-based quantum computing and for spintronics applications. Spin initialization, manipulation and readout are the three basic steps in the realization of quantum dot qubits. An electrical readout of the spin state is usually accomplished by spin-to-charge conversion schemes making the readout essentially a charge detection process. In the few-electron regime no measurable current flows through the device and the only way to probe the qubits is by charge detection. Moreover, transport measurements are invasive and will destroy the state of the qubit. In this talk I will discuss experiments on charge detection in Si/SiGe single and few-electron quantum dots using an integrated quantum point contact charge sensor, both in the time-averaged and single-shot detection modes. I will also discuss single-spin confinement in Si/SiGe single and double quantum dot systems and, excited state spectroscopy using gate voltage pulses. Time domain measurements showing real-time electron tunneling events and characterization of energy-dependent-tunneling in these devices will also be presented.