Strategies for enhancing spin-shuttling fidelities in Si/SiGe quantum wells with random-alloy disorder

Abstract

Coherent coupling between distant qubits is needed for any scalable quantum computing scheme. In quantum dot systems, one proposal for long-distance coupling is to coherently transfer electron spins across a chip in a moving potential. Here, we use simulations to study challenges for spin shuttling in Si/SiGe heterostructures caused by the valley degree of freedom. We show that for devices with valley splitting dominated by alloy disorder, one can expect to encounter pockets of low valley splitting, given a long-enough shuttling path. At such locations, inter-valley tunneling leads to dephasing of the spin wavefunction, substantially reducing the shuttling fidelity. We show how to mitigate this problem by modifying the heterostructure composition, or by varying the vertical electric field, the shuttling velocity, the shape and size of the dot, or the shuttling path. We further show that combinations of these strategies can reduce the shuttling infidelity by several orders of magnitude, putting shuttling fidelities sufficient for error correction within reach.

23 pages, 12 figures

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Cited by in corpus (14)

• Theory of Valley Splitting in Si/SiGe Spin-Qubits: Interplay of Strain, Resonances and Random Alloy Disorder
• Partial Landau-Zener transitions and applications to qubit shuttling
• 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
• Interplay of Zeeman Splitting and Tunnel Coupling in Coherent Spin Qubit Shuttling
• Electrical Interconnects for Silicon Spin Qubits
• The effects of alloy disorder on strongly-driven flopping mode qubits in Si/SiGe
• Omnidirectional shuttling to avoid valley excitations in Si/SiGe quantum wells
• Long-range spin transport in asymmetric quadruple quantum dots configurations
• Fabrication, characterization and mechanical loading of Si/SiGe membranes for spin qubit devices
• Digital-Controlled Method of Conveyor-Belt Spin Shuttling in Silicon for Large-Scale Quantum Computation
• Numerical simulation of coherent spin-shuttling in a QuBus with charged defects
• Exact Multi-Valley Envelope Function Theory of Valley Splitting in Si/SiGe Nanostructures