Summary
This work investigates spatial correlations in valley splitting across a silicon quantum well in SiGe heterostructures, revealing how microscopic alloy disorder affects spin qubit fidelity in industrially fabricated quantum dot devices using advanced pulsed spectroscopy techniques.
Highlights
- Silicon quantum wells in SiGe heterostructures host electron spin qubits for quantum computing.
- Valley splitting impacts spin qubit control and readout fidelity.
- Alloy disorder at interfaces dominates valley splitting variations.
- Detuning axis pulsed spectroscopy (DAPS) probes valley splitting spatially.
- Spatial correlations in valley splitting observed over a 1.3 µm device channel.
- Engineering quantum well potential and doping profiles can tune valley splitting.
- Findings aid scalable quantum dot qubit manufacturing with improved uniformity.
Key Insights
- Valley splitting limits qubit fidelity: Low-lying valley excited states reduce spin readout and control fidelity, representing a key challenge for high-performance silicon quantum processors.
- Microscopic disorder is dominant: Random alloy disorder and interface roughness critically influence valley splitting, causing spatial variability even in advanced semiconductor devices.
- Spatial correlations reveal disorder patterns: Measuring valley splitting along a 1.3 µm channel using DAPS uncovers non-trivial correlations tied to atomic-scale disorder distributions.
- DAPS enables detailed valley spectroscopy: The detuning axis pulsed spectroscopy technique provides a sensitive and spatially resolved probe of valley-orbital states in double quantum dot configurations.
- Engineering the quantum well controls valley splitting: Ge doping in the Si quantum well and surrounding SiGe alloy modifies valley coupling, providing a route to optimize valley splitting and qubit yields.
- Industrial fabrication meets fundamental challenges: Although CMOS-compatible SiGe quantum dot devices are scalable, achieving uniform valley splitting across large devices remains difficult due to intrinsic material fluctuations.
- Implications for scalable quantum computing: Understanding and mitigating valley splitting variability is essential for producing reliable qubits with gate fidelities above error correction thresholds in industrial settings.
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Citation
Marcks, J. C., Eagen, E., Brann, E. C., Losert, M. P., Oh, T., Reily, J., … Eriksson, M. A. (2025). Valley Splitting Correlations Across a Silicon Quantum Well (Version 1). arXiv. http://doi.org/10.48550/ARXIV.2504.12455