Bingjie Chen

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 [5]. 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 [6].

[1] Dodson, J.P. et al., arXiv:2103.14702 (2021).
[2] McJunkin, T. et al., Phys. Rev. B 104, 085406 (2021).
[3] Wuetz, B. P. et al., arXiv: 2112.09606 (2021).
[4] McJunkin, T. et al., arXiv: 2112.09765 (2021).
[5] Seidler, I. et al., arXiv:2108.00879 (2021).
[6] Hollman, A. et al., Phys. Rev. Applied 13, 034068 (2021).