Dressed photon-orbital states in a quantum dot: Inter-valley spin resonance

Abstract

The valley degree of freedom is intrinsic to spin qubits in Si/SiGe quantum dots. It has been viewed alternately as a hazard, especially when the lowest valley-orbit splitting is small compared to the thermal energy, or as an asset, most prominently in proposals to use the valley degree of freedom itself as a qubit. Here we present experiments in which microwave electric field driving induces transitions between both valley-orbit and spin states. We show that this system is highly nonlinear and can be understood through the use of dressed photon-orbital states, enabling a unified understanding of the six microwave resonance lines we observe. Some of these resonances are inter-valley spin transitions that arise from a non-adiabatic process in which both the valley and the spin degree of freedom are excited simultaneously. For these transitions, involving a change in valley-orbit state, we find a tenfold increase in sensitivity to electric fields and electrical noise compared to pure spin transitions, strongly reducing the phase coherence when changes in valley-orbit index are incurred. In contrast to this non-adiabatic transition, the pure spin transitions, whether arising from harmonic or subharmonic generation, are shown to be adiabatic in the orbital sector. The non-linearity of the system is most strikingly manifest in the observation of a dynamical anti-crossing between a spin-flip, inter-valley transition and a three-photon transition enabled by the strong nonlinearity we find in this seemly simple system.

23 pages, 11 figures, supplementary material included

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Cited by in corpus (25)

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• Large tunable valley splitting in edge-free graphene quantum dots on boron nitride
• Atomic fluctuations lifting the energy degeneracy in Si/SiGe quantum dots
• Blueprint of a scalable spin qubit shuttle device for coherent mid-range qubit transfer in disordered Si/SiGe/SiO${}_2$
• Valley dependent anisotropic spin splitting in silicon quantum dots
• Practical Strategies for Enhancing the Valley Splitting in Si/SiGe Quantum Wells
• Interface induced spin-orbit interaction in silicon quantum dots and prospects for scalability
• Semiconductor materials stacks for quantum dot spin qubits
• All-electrical manipulation of silicon spin qubits with tunable spin-valley mixing
• Low disorder and high valley splitting in silicon
• Nonlinear response and crosstalk of electrically driven silicon spin qubits
• Coherent spin-valley oscillations in silicon
• Controlling Synthetic Spin-Orbit Coupling in a Silicon Quantum Dot with Magnetic Field
• 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
• Interface and electromagnetic effects in the valley splitting of Si quantum dots
• Measurement-free implementations of small-scale surface codes for quantum dot qubits
• Effect of quantum Hall edge strips on valley splitting in silicon quantum wells
• 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
• The effects of alloy disorder on strongly-driven flopping mode qubits in Si/SiGe