A Solid-State Source of Single and Entangled Photons at Diamond SiV-Center Transitions Operating at 80K

Abstract

Large-scale quantum networks require the implementation of long-lived quantum memories as stationary nodes interacting with qubits of light. Epitaxially grown quantum dots hold great potential for the on-demand generation of single and entangled photons with high purity and indistinguishability. Coupling these emitters to memories with long coherence times enables the development of hybrid nanophotonic devices that incorporate the advantages of both systems. Here we report the first GaAs/AlGaAs quantum dots grown by the droplet etching and nanohole infilling method, emitting single photons with a narrow wavelength distribution (736.2 ± 1.7 nm) close to the zero-phonon line of silicon-vacancy centers. Polarization entangled photons are generated via the biexciton–exciton cascade with a fidelity of (0.73 ± 0.09). High single photon purity is maintained from 4 K (g(2)(0) = 0.07 ± 0.02) up to 80 K (g(2)(0) = 0.11 ± 0.01), therefore making this hybrid system technologically attractive for real-world quantum photonic applications.

Unveiling the 3D Morphology of Epitaxial GaAs/AlGaAs Quantum Dots

“…Smaller QDs tend to weaken the hyperfine interaction caused by the distance between electrons and nuclear spins and also show a significant inhibitory effect on spin–orbit coupling, thereby extending the spin coherence time. , In addition, reducing the compositional intermixing of AlGaAs and GaAs in the QDs will further extend the spin coherence time. , The energy of the confined exciton in DENI QD is mainly determined by the confinement in the growth direction and the infilling amount of GaAs. As a result, different filling amounts realize a wide distribution of exciton emission wavelengths. − Meanwhile, the weak confinement due to large lateral dimensions, which often exceed the free exciton Bohr radius in GaAs, shortens the exciton radiation lifetime . Therefore, a comprehensive understanding of the three-dimensional (3D) morphology of the DENI-based QD system is essential for optimizing the optical properties intrinsically.…”