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.

arXiv comment35 pages, 22 figures

References in corpus (45)

• Quantum Computation with Quantum Dots
• Silicon Quantum Electronics
• Computing with spin qubits at the surface code error threshold
• Fast universal quantum control above the fault-tolerance threshold in silicon
• Two-qubit silicon quantum processor with operation fidelity exceeding 99%
• Controllable valley splitting in silicon quantum devices
• Valley Splitting Theory of SiGe/Si/SiGe Quantum Wells
• Semiconductor Quantum Computation
• Valley splitting in strained silicon quantum wells
• A Reconfigurable Gate Architecture for Si/SiGe Quantum Dots
• Theory of valley-orbit coupling in a Si/SiGe quantum dot
• Interface roughness, valley-orbit coupling and valley manipulation in quantum dots
• Electrically Protected Valley-Orbit Qubits in Silicon
• Measurement of valley splitting in high-symmetry Si/SiGe quantum dots
• Magnetic field dependence of valley splitting in realistic Si/SiGe quantum wells
• Large, tunable valley splitting and single-spin relaxation mechanisms in a Si/Si${}_x$Ge${}_{1-x}$ quantum dot
• High Resolution Valley Spectroscopy of Si Quantum Dots
• Atomic fluctuations lifting the energy degeneracy in Si/SiGe quantum dots
• Intervalley coupling for interface-bound electrons in silicon: An effective mass study
• Tunable singlet-triplet splitting in a few-electron Si/SiGe quantum dot
• SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits
• Single-Spin Relaxation in a Synthetic Spin-Orbit Field
• Multivalley effective mass theory simulation of donors in silicon
• Valley dependent anisotropic spin splitting in silicon quantum dots
• Genetic Design of Enhanced Valley Splitting towards a Spin Qubit in Silicon
• Valley splitting of single-electron Si MOS quantum dots
• Disorder-induced valley-orbit hybrid states in Si quantum dots
• Strong electron-electron interactions in Si/SiGe quantum dots
• Valley splittings in Si/SiGe quantum dots with a germanium spike in the silicon well
• Detuning Axis Pulsed Spectroscopy of Valley-Orbital States in Si/SiGe Quantum Dots
• Control of valley dynamics in silicon quantum dots in the presence of an interface step
• The critical role of substrate disorder in valley splitting in Si quantum wells
• How valley-orbit states in silicon quantum dots probe quantum well interfaces
• Dressed photon-orbital states in a quantum dot: Inter-valley spin resonance
• Electromagnetic control of valley splitting in ideal and disordered Si quantum dots
• Effects of Interface Steps on the Valley Orbit coupling in a Si/SiGe quantum dot
• Switching between relaxation hotspots and coldspots in disordered spin qubits
• Extended interface states enhance valley splitting in Si/SiO2
• Enhanced Valley Splitting in Si Layers with Oscillatory Ge Concentration
• Signatures of atomic-scale structure in the energy dispersion and coherence of a Si quantum-dot qubit
• Cryogen-free scanning gate microscope for the characterization of Si/Si${}_{0.7}$Ge${}_{0.3}$ quantum devices at milli-Kelvin temperatures
• Origin of giant valley splitting in silicon quantum wells induced by superlattice barriers
• Multiscale theory of valley splitting
• Calculation of tunnel-couplings in open gate-defined disordered quantum dot systems
• Charge-noise resilience of two-electron quantum dots in Si/SiGe heterostructures

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