Hybrid acousto-optical spin control in quantum dots

TL;DR

This paper introduces a hybrid acousto-optical method for controlling spins in quantum dots, enabling high-fidelity spin rotations via acoustic and optical coupling, which could facilitate integrated quantum hybrid systems.

Contribution

It proposes a novel hybrid acousto-optical spin control technique that combines optical and acoustic fields to achieve efficient spin rotations in quantum dots.

Findings

High spin rotation fidelity (>99.9%) achievable with current technology.

Spin control is compatible with noise mitigation pulse sequences.

Method enables potential transduction between acoustic, optical, and microwave domains.

Abstract

Mechanical degrees of freedom very weakly couple to spins in semiconductors. The inefficient coupling between phonons and single electron spins in semiconductor quantum dots (QDs) hinders their integration into on-chip acoustically coupled quantum hybrid systems. We propose a hybrid acousto-optical spin control method that circumvents this problem and effectively introduces acoustic spin rotation to QDs, complementing their rich couplings with external fields and quantum registers. We show that combining continuous-wave detuned optical coupling to a trion state and acoustic modulation results in spin rotation around an axis defined by the acoustic field. The optical field breaks spin conservation, allowing phonons to drive transitions between disrupted spin states when at resonance with the Zeeman frequency. Our method is compatible with pulse sequences that mitigate quasi-static noise effects, which makes trion recombination the primary limitation to gate fidelity under cooled nuclear-spin conditions. Numerical simulations indicate that spin rotation fidelity can be very high, if the trion lifetime is long and Zeeman splitting is sufficiently large, with a currently feasible 50~ns lifetime and 44~GHz splitting giving 99.9\% fidelity. Applying our advancement could enable acoustic QD spin state transfer to diverse solid-state systems and transduction between acoustic, optical, and microwave domains, all within an on-chip integration-ready setting.