Abstract
Once the periodic properties of elements were unveiled, chemical behaviour could be understood in terms of the valence of atoms. Ideally, this rationale would extend to quantum dots, and quantum computation could be performed by merely controlling the outer-shell electrons of dot-based qubits. Imperfections in semiconductor materials disrupt this analogy, so real devices seldom display a systematic many-electron arrangement. We demonstrate here an electrostatically confined quantum dot that reveals a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom. Various fillings containing a single valence electron—namely 1, 5, 13 and 25 electrons—are found to be potential qubits. An integrated micromagnet allows us to perform electrically-driven spin resonance (EDSR), leading to faster Rabi rotations and higher fidelity single qubit gates at higher shell states. We investigate the impact of orbital excitations on single qubits as a function of the dot deformation and exploit it for faster qubit control.
Highlights
Once the periodic properties of elements were unveiled, chemical behaviour could be understood in terms of the valence of atoms
The scanning electron microscope (SEM) image in Fig. 1a shows a silicon metal-oxide-semiconductor (Si-MOS) device that forms a quantum dot at the Si/SiO2 interface under gate G1, separated from the reservoir by a barrier that is controlled by gate G2—see Fig. 1b for a cross-sectional representation
The results presented here experimentally demonstrate that robust spin qubits can be implemented in multielectron quantum dots up to at least the third valence shell
Summary
Once the periodic properties of elements were unveiled, chemical behaviour could be understood in terms of the valence of atoms. Qubit architectures based on electron spins in gatedefined silicon quantum dots benefit from a high level of controllability, where single and multi-qubit coherent operations are realised solely with electrical and magnetic manipulation.
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