Polarimetry With Spins in the Solid State

TL;DR

This paper extends traditional polarimetry to spin systems in solid-state quantum devices, demonstrating how spin-orbit coupling causes misalignment that limits spin readout fidelity in silicon quantum dots.

Contribution

It introduces a polarimetry-based approach to analyze spin readout in semiconductor quantum dots, highlighting the impact of spin-orbit coupling on fidelity.

Findings

Spin-orbit coupling induces spin misalignment.

Rotating magnetic field can recover spin alignment.

Misalignment limits spin readout fidelity.

Abstract

The ability for optically active media to rotate the polarization of light is the basis of polarimetry, an illustrious technique responsible for many breakthroughs in fields as varied as astronomy, medicine and material science. Here, we recast the primary mechanism for spin readout in semiconductor-based quantum computers, Pauli spin-blockade (PSB), as the natural extension of polarimetry to the third dimension. We perform polarimetry with spins through a silicon quantum dot exchanging a hole with a boron acceptor, demonstrating the role of spin-orbit coupling in creating spin misalignment. Perfect spin alignment may be recovered by means of rotating the applied magnetic-field orientation. This work shows how spin misalignment sets a fundamental upper limit for the spin readout fidelity in quantum-computing systems based on PSB.