QDs for Quantum - Project Presentation GREENER

Figure 1: Scheme of the Quantum Dot single-photon source in the GREENER project.

Fraunhofer ENAS has many years of experience in developing and optimizing Quantum Dot LEDs (QD-LEDs) in the visible and NIR spectral range. By reducing the number of colloidal quantum dots in the emitter layer to a single nanocrystal, electrically excited single-photon sources can be realized based on the LEDs.

Single-photon sources (SPS) have great potential for use in various areas of quantum technology, including quantum information processing, for example, for secure encryption in data transmission (Quantum Key Distribution). These light sources are also interesting for metrology, for instance for optical and spectroscopic analyses. Due to the quantum mechanical properties of the SPS, the emitted photons follow a different statistic than classical light sources. This allows for reduced noise, for example, in absorption measurements, and significantly increased sensitivity.

In the EU-funded project GREENER, Fraunhofer ENAS, in cooperation with Chemnitz University of Technology and six other partners from France, Italy, Spain, and Germany, is developing a novel spectrometer based on electrically excited QD single-photon sources (QD-SPS) and optimized single-photon detectors. The goal is to determine the smallest concentrations of environmentally harmful substances, such as in water, using NIR absorption spectroscopy.

The structure of the colloidal QD-SPS is schematically shown in Figure 1. A key element in building these sources is the nanometer-precise positioning of individual quantum dots. In the project, this is achieved using so-called DNA origamis. A DNA origami consists of a single strand of DNA that can be folded into any 2D and 3D geometry with the help of short staple strands (oligonucleotides). Through so-called "capture ends," individual QDs can be specifically attached. These hybrids are then deposited with nanometer precision at the wafer level supported by lithography.

These single-photon sources are integrated with other optical components and a single-photon detector into a compact spectrometer for mobile analysis. Corresponding electronics and AI-based data processing complete the device. An overview of the project and its goals is given not only on the website but also in a video.