Bounds to electron spin qubit variability for scalable CMOS architectures

Abstract

Spins of electrons in CMOS quantum dots combine exquisite quantum properties and scalable fabrication. In the age of quantum technology, however, the metrics that crowned Si/SiO2 as the microelectronics standard need to be reassessed with respect to their impact upon qubit performance. We chart the spin qubit variability due to the unavoidable atomic-scale roughness of the Si/SiO${}_2$ interface, compiling experiments in 12 devices, and developing theoretical tools to analyse these results. Atomistic tight binding and path integral Monte Carlo methods are adapted for describing fluctuations in devices with millions of atoms by directly analysing their wavefunctions and electron paths instead of their energy spectra. We correlate the effect of roughness with the variability in qubit position, deformation, valley splitting, valley phase, spin-orbit coupling and exchange coupling. These variabilities are found to be bounded and lie within the tolerances for scalable architectures for quantum computing as long as robust control methods are incorporated.

20 pages, 8 figures

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• Assessment of error variation in high-fidelity two-qubit gates in silicon
• A 300 mm foundry silicon spin qubit unit cell exceeding 99% fidelity in all operations
• High-fidelity spin qubit shuttling via large spin-orbit interaction
• Towards early fault tolerance on a 2$\times$N array of qubits equipped with shuttling
• Violating Bell's inequality in gate-defined quantum dots
• Entangling gates on degenerate spin qubits dressed by a global field
• Impact of electrostatic crosstalk on spin qubits in dense CMOS quantum dot arrays
• Quantum geometric protocols for fast high-fidelity adiabatic state transfer
• A 2x2 quantum dot array in silicon with fully tuneable pairwise interdot coupling
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• A SWAP Gate for Spin Qubits in Silicon
• Variability of hole spin qubits in planar Germanium
• Concatenated continuous driving of silicon qubit by amplitude and phase modulation