Practical Strategies for Enhancing the Valley Splitting in Si/SiGe Quantum Wells

Abstract

Silicon/silicon-germanium heterostructures have many important advantages for hosting spin qubits. However, controlling the valley splitting (the energy splitting between the two low-lying conduction-band valleys) remains a critical challenge for ensuring qubit reliability. Broad distributions of valley splittings are commonplace, even among quantum dots formed on the same chip. In this work, we theoretically explore the interplay between quantum-well imperfections that suppress the valley splitting and cause variability, such as broadened interfaces and atomic steps at the interface, while self-consistently accounting for germanium concentration fluctuations. We consider both conventional and unconventional approaches for controlling the valley splitting, and present concrete strategies for implementing them. Our results provide a clear path for achieving qubit uniformity in a scalable silicon quantum computer.

35 pages, 22 figures

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Cited by in corpus (31)

• Probing single electrons across 300 mm spin qubit wafers
• Spin-EPR-pair separation by conveyor-mode single electron shuttling in Si/SiGe
• Low disorder and high valley splitting in silicon
• Mapping of valley-splitting by conveyor-mode spin-coherent electron shuttling
• Utilizing multimodal microscopy to reconstruct Si/SiGe interfacial atomic disorder and infer its impacts on qubit variability
• Strategies for enhancing spin-shuttling fidelities in Si/SiGe quantum wells with random-alloy disorder
• Valley-Polarized quantum Hall phase in a strain-controlled Dirac system
• Coupling conduction-band valleys in SiGe heterostructures via shear strain and Ge concentration oscillations
• Atomistic compositional details and their importance for spin qubits in isotope-purified silicon-germanium quantum wells
• Valley splitting depending on the size and location of a silicon quantum dot
• Theory of Valley Splitting in Si/SiGe Spin-Qubits: Interplay of Strain, Resonances and Random Alloy Disorder
• Local laser-induced solid-phase recrystallization of phosphorus-implanted Si/SiGe heterostructures for contacts below 4.2 K
• Atomistic insights into ultrafast SiGe nanoprocessing
• Decoherence of electron spin qubit during transfer between two semiconductor quantum dots at low magnetic fields
• Valley Splitting Correlations Across a Silicon Quantum Well Containing Germanium
• Suppressing Si Valley Excitation and Valley-Induced Spin Dephasing for Long-Distance Shuttling
• Minimal evolution times for fast, pulse-based state preparation in silicon spin qubits
• Electrical Interconnects for Silicon Spin Qubits
• Omnidirectional shuttling to avoid valley excitations in Si/SiGe quantum wells
• Proposed Five-Electron Charge Quadrupole Qubit
• Towards Utilizing Scanning Gate Microscopy as a High-Resolution Probe of Valley Splitting in Si/SiGe Heterostructures
• Decoherence and fidelity enhancement during shuttling of entangled spin qubits
• Fabrication, characterization and mechanical loading of Si/SiGe membranes for spin qubit devices
• The effects of alloy disorder on strongly-driven flopping mode qubits in Si/SiGe
• Micromagnet-free operation of electron spin qubits in Si/Si${}_{1-x}$Ge${}_x$ vertical double quantum dots
• Effects of valley splitting on resonant-tunneling readout of spin qubits
• Exact Multi-Valley Envelope Function Theory of Valley Splitting in Si/SiGe Nanostructures
• Digital-Controlled Method of Conveyor-Belt Spin Shuttling in Silicon for Large-Scale Quantum Computation
• Negative exchange interaction in Si quantum dot arrays via valley-phase induced ${\mathbb{Z}}_2$ gauge field
• Wide Electrical Tunability of the Valley Splitting in a Doubly gated Silicon-on-Insulator Quantum Well
• Numerical simulation of coherent spin-shuttling in a QuBus with charged defects