Imagine a future where digital information is fundamentally secure, powerful new computers solve problems beyond the reach of today’s machines, and communication networks operate using the laws of quantum physics. Realizing this vision depends on one deceptively demanding component: a source that can emit single particles of light, known as photons, one by one, with high brightness, exceptional purity, and nearly identical properties. Although remarkable progress has been made in recent years, producing many such sources in a scalable manner on a semiconductor chip has remained one of quantum technology’s most persistent challenges. Researchers now report an important step toward overcoming this barrier.
In a new paper published in Light: Science & Applications , Kartik Gaur and co-workers, under the leadership of Prof. Stephan Reitzenstein at the Technical University of Berlin, together with collaborators from the group of Prof. Christopher Gies at Carl von Ossietzky University of Oldenburg, have developed a scalable quantum photonic chip architecture that integrates deterministically positioned semiconductor quantum emitters into nanoscale photonic resonators. The result is a platform capable of generating bright, pure, and highly indistinguishable single photons, key resources for quantum communication, quantum networks, and optical quantum computing.
At the heart of the technology are quantum dots, nanoscale structures often described as artificial atoms because they can emit single photons with exceptional quantum control. In conventional approaches, however, such emitters form at random positions during growth. Suitable quantum dots must therefore be identified individually before photonic devices can be fabricated around them, a highly successful strategy for single demonstrator devices, but one that becomes increasingly demanding when extended to wafer-scale arrays containing hundreds or thousands of emitters.
TU Berlin researchers addressed this challenge using a deterministic growth concept based on a buried-stressor layer that guide each quantum dot into predefined positions during crystal growth. These site-controlled emitters are then directly integrated into circular Bragg grating resonators, compact nanophotonic structures designed to efficiently extract and direct the emitted light.
Using this concept, the team fabricated a 6×6 array with 100% yield of working devices, demonstrating a level of reproducibility rarely achieved in solid-state quantum photonics. Rather than relying on a single optimized structure, the study shows that high-performance quantum light sources can be realized repeatedly across an integrated semiconductor chip platform.
The best-performing device delivered an exceptional combination of metrics: nearly half of the generated photons were extracted into the collection optics, single-photon purity exceeded 99%, narrow optical linewidths were maintained, and two-photon interference measurements revealed high indistinguishability, a key requirement for advanced photonic quantum processors.
Equally important, the researchers established how nanometer-scale emitter misalignment influences device performance. By combining structural imaging, optical spectroscopy, lifetime analysis, photon-correlation measurements, two-photon interference experiments, and electromagnetic simulations, they identified quantitative fabrication tolerances relevant for future large-scale device integration.
The team from Carl von Ossietzky University of Oldenburg, led by Prof. Christopher Gies, carried out the quantum-optical modelling, providing a theoretical framework that explains how emitter position influences charge-noise-induced decoherence and directly links fabrication accuracy to linewidth broadening and photon indistinguishability. The close agreement between experiment and theory provides valuable design rules for next-generation quantum photonic chips.
The authors say that the work addresses a longstanding bottleneck in the field: not simply whether one excellent quantum light source can be demonstrated, but whether many can be fabricated with predictable quality on the same wafer. The marker-free integration strategy removes the need for labor-intensive emitter localization and alignment procedures that have traditionally limited scalability.
Beyond the immediate device performance, the technology offers a realistic route toward wafer-scale quantum photonic hardware using established semiconductor manufacturing methods. This could accelerate the development of secure quantum communication systems, compact quantum sensors, and optical quantum computing architectures based on large arrays of deterministic single-photon sources.
The researchers describe the platform as an important transition from individually optimized laboratory devices toward reproducible quantum photonic technologies manufactured with the precision, uniformity, and scale required for practical applications.
Light: Science & Applications
Scalable Quantum Photonic Platform Based on Site-Controlled Quantum Dots Coupled to Circular Bragg Grating Resonators