Atomic fluctuations lifting the energy degeneracy in Si/SiGe quantum dots

Abstract

Electron spins in Si/SiGe quantum wells suffer from nearly degenerate conduction band valleys, which compete with the spin degree of freedom in the formation of qubits. Despite attempts to enhance the valley energy splitting deterministically, by engineering a sharp interface, valley splitting fluctuations remain a serious problem for qubit uniformity, needed to scale up to large quantum processors. Here, we elucidate and statistically predict the valley splitting by the holistic integration of 3D atomic-level properties, theory and transport. We find that the concentration fluctuations of Si and Ge atoms within the 3D landscape of Si/SiGe interfaces can explain the observed large spread of valley splitting from measurements on many quantum dot devices. Against the prevailing belief, we propose to boost these random alloy composition fluctuations by incorporating Ge atoms in the Si quantum well to statistically enhance valley splitting.

References in corpus (8)

• Computing with spin qubits at the surface code error threshold
• Fast universal quantum control above the fault-tolerance threshold in silicon
• Scalable gate architecture for densely packed semiconductor spin qubits
• A Reconfigurable Gate Architecture for Si/SiGe Quantum Dots
• Measurement of valley splitting in high-symmetry Si/SiGe quantum dots
• Magnetic field dependence of valley splitting in realistic Si/SiGe quantum wells
• SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits
• Strong electron-electron interactions in Si/SiGe quantum dots

Cited by in corpus (41)

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• Blueprint of a scalable spin qubit shuttle device for coherent mid-range qubit transfer in disordered Si/SiGe/SiO${}_2$
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• The SpinBus Architecture: Scaling Spin Qubits with Electron Shuttling
• Practical Strategies for Enhancing the Valley Splitting in Si/SiGe Quantum Wells
• Shuttling an electron spin through a silicon quantum dot array
• Low charge noise quantum dots with industrial CMOS manufacturing
• Low disorder and high valley splitting in silicon
• Electrical control of uniformity in quantum dot devices
• 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
• Enhanced Valley Splitting in Si Layers with Oscillatory Ge Concentration
• Strategies for enhancing spin-shuttling fidelities in Si/SiGe quantum wells with random-alloy disorder
• Interface and electromagnetic effects in the valley splitting of Si quantum dots
• Simulation of 1/f charge noise affecting a quantum dot in a Si/SiGe structure
• Spin-orbit enhancement in Si/SiGe heterostructures with oscillating Ge concentration
• Single-electron occupation in quantum dot arrays at selectable plunger gate voltage
• 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-Free Silicon Fins Caused by Shear Strain
• Valley splitting depending on the size and location of a silicon quantum dot
• Nuclear Spin-Depleted, Isotopically Enriched 70Ge/28Si70Ge Quantum Wells
• Flopping-mode electron dipole spin resonance in the strong-driving regime
• Theory of Valley Splitting in Si/SiGe Spin-Qubits: Interplay of Strain, Resonances and Random Alloy Disorder
• Thin films as practical quantum materials: a status quo and beyond
• Reducing disorder in Ge quantum wells by using thick SiGe barriers
• Local laser-induced solid-phase recrystallization of phosphorus-implanted Si/SiGe heterostructures for contacts below 4.2 K
• 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
• Scalable and Tunable In-Plane Ge/Si(001) Nanowires Grown by Molecular Beam Epitaxy
• Scalable Parity Architecture With a Shuttling-Based Spin Qubit Processor
• Fabrication, characterization and mechanical loading of Si/SiGe membranes for spin qubit devices
• Omnidirectional shuttling to avoid valley excitations in Si/SiGe quantum wells
• Micromagnet-free operation of electron spin qubits in Si/Si${}_{1-x}$Ge${}_x$ vertical double quantum dots
• The effects of alloy disorder on strongly-driven flopping mode qubits in Si/SiGe
• Towards Utilizing Scanning Gate Microscopy as a High-Resolution Probe of Valley Splitting in Si/SiGe Heterostructures
• Numerical simulation of coherent spin-shuttling in a QuBus with charged defects
• Digital-Controlled Method of Conveyor-Belt Spin Shuttling in Silicon for Large-Scale Quantum Computation
• Interplay of Pauli blockade with electron-photon coupling in quantum dots
• 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