Qubits based on gate-defined Si/SiGe quantum dots (QD) are one of the major candidates for the solid-state implementation of quantum information processing. With its weak spin- orbit coupling and low hyperfine interaction, it has overcome the fidelity threshold for quantum error correction and high-fidelity qubit readout has become accessible. Besides these attractive properties, the magnitude and homogeneity of the valley splitting in silicon quantum dots remain a challenge. The existence of valley-state excitation has implications from spin decoherence to exchange, and many other aspects of spin-based qubits. Thus, the characterization of the valley splitting is critical for the scalability of silicon-based qubits and has been intensively investigated recently [1-4].
In our experiments, we carry out the valley splitting measurements at different locations on the same sample, where the experiment of shuttling of a single electron was reported earlier . The lower boundary of the relevant valley splitting energy is measured with various QD fillings-states using magneto-spectroscopy [2,3]. Pulsed-gate spectroscopy is also introduced to give a glance at valley-splitting and orbital energy, which can be extracted based on Radon-transformation. These results will be compared to our previous results measured in a Si/SiGe double QD by pulsed-gate spectroscopy and magnetic field dependence of the spin-relaxation time .
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