Angular momentum transfer from photon polarization to an electron spin in a gate-defined quantum dot

Takafumi Fujita,Marcus Larsson,Akira Oiwa,Giles Allison,Kazuhiro Morimoto,Andreas D Wieck,Arne Ludwig,Haruki Kiyama,Seigo Tarucha,Sascha R Valentin

doi:10.1038/s41467-019-10939-x

Abstract

Gate-defined quantum dots (QDs) are such a highly-tunable quantum system in which single spins can be electrically coupled, manipulated, and measured. However, the spins in gate-defined QDs are lacking its interface to free-space photons. Here, we verify that a circularly-polarized single photon can excite a single electron spin via the transfer of angular momentum, measured using Pauli spin blockade (PSB) in a double QD. We monitor the inter-dot charge tunneling which only occur when the photo-electron spin in one QD is anti-parallel to the electron spin in the other. This allows us to detect single photo-electrons in the spin-up/down basis using PSB. The photon polarization dependence of the excited spin state was finally confirmed for the heavy-hole exciton excitation. The angular momentum transfer observed here is a fundamental step providing a route to instant injection of spins, distributing single spin information, and possibly towards extending quantum communication.

Highlights

Gate-defined quantum dots (QDs) are such a highly-tunable quantum system in which single spins can be electrically coupled, manipulated, and measured
Gated QDs in a quantum well may be appropriate for these purposes because the orbital and spin angular momenta are well-defined by the strong vertical confinement and suitable for the transition with angular momentum selection rule, while the soft lateral confinement will least affect the selection rule for the optical excitation
Investigating the singly excited charged spin electrically is essential for understanding the selection rule in the optical excitation, robustness of the photo-generated electron spin, and for applications in nano-scaled spin-based information processing13,14, but a challenging task

Summary

Introduction

Gate-defined quantum dots (QDs) are such a highly-tunable quantum system in which single spins can be electrically coupled, manipulated, and measured. Using this reliable condition, we verify the principle selection rule from a single circularly polarized photon to the excited single electron spin state at the HH exciton by rotating the incident polarization

Methods

Results

Conclusion