Low-noise GaAs quantum dots for quantum photonics

Abstract

Quantum dots are both excellent single-photon sources and hosts for single spins. This combination enables the deterministic generation of Raman-photons—bandwidth-matched to an atomic quantum-memory—and the generation of photon cluster states, a resource in quantum communication and measurement-based quantum computing. GaAs quantum dots in AlGaAs can be matched in frequency to a rubidium-based photon memory, and have potentially improved electron spin coherence compared to the widely used InGaAs quantum dots. However, their charge stability and optical linewidths are typically much worse than for their InGaAs counterparts. Here, we embed GaAs quantum dots into an n-i-p-diode specially designed for low-temperature operation. We demonstrate ultra-low noise behaviour: charge control via Coulomb blockade, close-to lifetime-limited linewidths, and no blinking. We observe high-fidelity optical electron-spin initialisation and long electron-spin lifetimes for these quantum dots. Our work establishes a materials platform for low-noise quantum photonics close to the red part of the spectrum.

Quantum key distribution with entangled photons generated on demand by a quantum dot

“…The probability of creating an entangled photon pair at any time is lower because of blinking dynamics that can cause the QD to stay optically inactive on the microsecond time scale. In our work, we have observed ( 32 ) characteristic on-time fractions of 0.22 to 0.26, which, however, do not imply any fundamental limitation, as complete blinking suppression has been experimentally demonstrated ( 33 ).…”

“…on March 29, 2021 http://advances.sciencemag.org/ Downloaded from (32) characteristic on-time fractions of 0.22 to 0.26, which, however, do not imply any fundamental limitation, as complete blinking suppression has been experimentally demonstrated (33).…”

Chip-Scale Quantum Emitters

“…The linewidth of the established platform is close to lifetime-limited linewidths. High-fidelity optical electron-spin initialization and long electron-spin lifetimes for these quantum dots were observed [39]. Hu et al [40] explained the direct two-photon excitation effect on the photoluminescence of self-assembled InAs/GaAs quantum dots grown by molecular beam epitaxy.…”

“…Schuck and co-workers [38] presented a novel semiconductor single-photon source based on tensile-strained (111)-oriented GaAs/InAlAs quantum dots (QDs) exhibiting ultrasmall exciton fine-structure splitting (FSS) of ≤8 µeV. Due to the possibility of frequency matching between a rubidium-based photon memory and embedded GaAs QDs in an AlGaAs matrix, they have potentially improved electron spin coherence compared to the widely used InGaAs quantum dots [39]. To provide their charge stability and optical linewidths, GaAs quantum dots were embedded into a p-i-n (PIN) diode that operated at low temperatures and demonstrated ultralow noise behavior.…”

Nanoscale Positioning Approaches for Integrating Single Solid‐State Quantum Emitters with Photonic Nanostructures

“…With aid from nanoscale positioning tools, more efforts are expected to help understand how to recover the Fourier transform limited single‐photons from QDs broadened by the etched surfaces, for example, exploring surface passivation and oxide encapsulation [ 66 ] to improve optical properties of QDs and using gated structures to control the local charge environment. [ 67,68 ]…”