CANCELLED

Physical Society Colloquium

Quantum information processing with spins

Bill Coish

Department of Physics
McGill University

A scalable quantum computer could achieve feats of computation and simulation that would be unimaginable with present-day technology. Although some of the theoretical building blocks required for quantum computation (certain algorithms and error-correction procedures) have been well established over the past 20 years, designing and building a viable scalable quantum processor remains a significant practical challenge. Single electron spins in semiconductor quantum dots are a promising way forward: A qubit that is small, very long-lived, fast, and can take advantage of existing large-scale fabrication methods. For this architechture, the first quantum algorithms have now been demonstrated in a very small two-qubit prototype [1]. I will review recent progress in this field with an emphasis on spin-qubit measurement (readout). Readout is a complex problem that marries nanoelectronic transport, nonequilibrium quantum dynamics, quantum measurements, and signal processing. It often requires the development of advanced inference procedures. These inference procedures allow for improved measurements and may help with quantum error correction, where syndrome measurements are frequent. One such example, a soft-decision decoder applied to a repetition code for spin qubits [2], has been characterized experimentally very recently in a two-qubit processor [3].

[1] TF Watson et al., Nature 555, 633 (2018)
[2] B D'Anjou and WA Coish, Phys. Rev. Lett. 113, 230402 (2014)
[3] X Xue, B D'Anjou, et al., arXiv:1911.08420