In the realm of quantum technologies, a team of researchers from the Technical University of Berlin, led by Stephan Reitzenstein, has made significant strides in integrating quantum emitters into photonic nanostructures. Their work, published in the journal Nature Communications, addresses a critical challenge in the field of quantum photonics: the precise and scalable integration of quantum dots with photonic structures.
The researchers have developed a novel approach that leverages site-controlled quantum dots (QDs) coupled to circular Bragg grating (CBG) resonators. This method eliminates the need for complex and time-consuming deterministic lithography techniques, which have been traditionally used to align quantum dots with photonic structures. Instead, the team uses a buried-stressor-based site-controlled InGaAs QD platform that allows for precise spatial alignment with CBG resonators.
The team fabricated a 6×6 array of these QD-CBG devices, achieving a 100% device yield. Impressively, 35 of these devices fell within the radial-offset range where the simulated photon-extraction efficiency (PEE) exceeds 20%, demonstrating the spatial precision and scalability of their fabrication concept.
The researchers then selected a subset of five devices with varying radial displacements to study the effects of spatial alignment on extraction efficiency, spectral linewidth, and photon indistinguishability. They found clear offset-dependent trends in these properties, establishing quantitative bounds on spatial alignment tolerances.
In the best-aligned QD-CBG device, the team achieved a PEE of 47.1%, a linewidth of 1.41 GHz, a radiative decay lifetime of 0.80 ns, a single-photon purity of 99.58%, and a Hong-Ou-Mandel two-photon interference visibility of 81% under quasi-resonant excitation at saturation power. These results represent a significant advancement in the field of quantum photonics.
The practical applications of this research for the energy sector are still in the early stages, but the potential is substantial. Quantum technologies could revolutionize energy systems by enabling ultra-secure communication networks, enhancing computational power for complex energy modeling, and improving sensing and monitoring capabilities for energy infrastructure. The precise control and manipulation of quantum states demonstrated in this research could be a key step towards realizing these applications.
The research was published in Nature Communications, a peer-reviewed, open-access, multidisciplinary journal of scientific research.
This article is based on research available at arXiv.