arXiv subjects

Tjorben Matthes

Publications and source records attributed to Tjorben Matthes.

5 recordsLinked to original sources

arXiv2026

A proposal for a hybrid free-space optical quantum communication network with hexagonal boron nitride-based single photon sources

Hexagonal boron nitride (hBN) is known as a promising solid-state platform to host room temperature quantum emitters that produce high purity single photons. The bright and spectrally adaptable hBN emitters are space-compatible, making hBN well-suited for satellite-based free-space optical (FSO) quantum key distribution (QKD) at wavelengths where the atmospheric background is naturally suppressed. This paper presents a pathway to develop hBN emitters operating near the Ca-II Fraunhofer line (at 854 nm), enabling daylight FSO operation. Moreover, due to its compatibility with the first telecommunication window at 850 nm, it is possible to interface with optical fibers to bridge the `last mile' in a scenario where multiple end-users connect through a single optical ground station to a QKD satellite. We therefore introduce a concept that combines continuous operation of a quantum network, hybrid links to minimize deployment costs, and high data rates due to the use of realistic single photon sources. The realization would be an important milestone for the development of the quantum internet.

quant-ph↗

arXiv2026

QuaNTUM: A Modular Quantum Communication Testbed for Scalable Fiber and Satellite Integration

Secure communication is essential for modern society, from financial transactions to critical infrastructure. As classical encryption faces threats from advancing computational power, quantum communication provides a fundamentally secure alternative based on physical laws. We present QuaNTUM (Quantum Network at the Technical University of Munich), a modular and extensible quantum communication testbed enabling scalable experiments across fiber-based campus networks and satellite-ground links. The terrestrial network connects research institutions in Garching near Munich via single-mode fibers in a star topology with polarization-maintaining components, multiplexers, and time-synchronized analysis modules. Active polarization control and real-time feedback support stable qubit transmission for high-fidelity quantum key distribution and entanglement distribution. A key feature is the integration of deterministic solid-state single-photon sources, including defects in hexagonal boron nitride and excited erbium atoms, with initial deployments on small satellites to bridge terrestrial and free-space channels. As an open-access platform, QuaNTUM enables protocol development, device benchmarking, and hybrid network research, providing a foundation for scalable quantum communication and future global quantum networks.

quant-ph↗

arXiv2024

Comparative study of quantum emitter fabrication in wide bandgap materials using localized electron irradiation

Quantum light sources are crucial foundational components for various quantum technology applications. With the rapid development of quantum technology, there has been a growing demand for materials with the capability of hosting quantum emitters. One such material platform uses fluorescent defects in hexagonal boron nitride (hBN) that can host deep sublevels within the bandgap. The localized electron irradiation has shown its effectiveness in generating deep sublevels to induce single emitters in hBN. The question is whether localized (electron beam) irradiation is a reliable tool for creating emitters in other wide bandgap materials and its uniqueness to hBN. Here, we investigate and compare the fabrication of quantum emitters in hBN and exfoliated muscovite mica flakes along with other 3D crystals, such as silicon carbide and gallium nitride, which are known to host quantum emitters. We used our primary fabrication technique of localized electron irradiation using a standard scanning electron microscope. To complement our experimental work, we employed density functional theory simulations to study the atomic structures of defects in mica. While our fabrication technique allows one to create hBN quantum emitters with a high yield and high single photon purity, it is unable to fabricate single emitters in the other solid-state crystals under investigation. This allows us to draw conclusions on the emitter fabrication mechanism in hBN, which could rely on activating pre-existing defects by charge state manipulation. Therefore, we provide an essential step toward the identification of hBN emitters and their formation process.

physics.app-ph↗

arXiv2024

Polarization dynamics of solid-state quantum emitters

Quantum emitters in solid-state crystals have recently attracted a lot of attention due to their simple applicability in optical quantum technologies. The polarization of single photons generated by quantum emitters is one of the key parameters that play a crucial role in the applications, such as quantum computation that uses the indistinguishability of photons. However, the degree of single photon polarization is typically quantified using time-averaged photoluminescence intensity of single emitters, which provides limited information about the dipole properties in solids. In this work, we use single defects in hexagonal boron nitride and nanodiamond as efficient room-temperature single photon sources to reveal the origin and the temporal evolution of dipole orientation in solid-state quantum emitters. The angle of excitation and emission dipoles relative to the crystal axes are determined experimentally and then calculated using density functional theory, which results in characteristic angles for every specific defect that can be used as an efficient tool for defect identification and understanding their atomic structure. Moreover, the temporal polarization dynamics reveal a strongly modified linear polarization visibility that depends on the excited state decay time of individual excitation. This effect can be traced back potentially to the excitation of excess charges in the local crystal environment. Understanding such hidden time-dependent mechanisms can further be used to improve the performance of polarization-sensitive experiments, in particular that of quantum communication with single photon emitters.

quant-ph↗

arXiv2023

Localized creation of yellow single photon emitting carbon complexes in hexagonal boron nitride

Single photon emitters in solid-state crystals have received a lot of attention as building blocks for numerous quantum technology applications. Fluorescent defects in hexagonal boron nitride (hBN) stand out due to their high luminosity and robust operation at room temperature. The identical emitter fabrication at pre-defined sites is still challenging, which hampers the integration of these defects in optical systems and electro-optical devices. Here, we demonstrate the localized fabrication of hBN emitter arrays by electron beam irradiation using a standard scanning electron microscope with deep sub-micron lateral precision. The emitters are created with a high yield and a reproducible spectrum peaking at 575 nm. Our measurements of optically detected magnetic resonance have not revealed any addressable spin states. Using density functional theory, we attribute the experimentally observed emission lines to carbon-related defects, which are activated by the electron beam. Our scalable approach provides a promising pathway for fabricating room temperature single photon emitters in integrated quantum devices.

quant-ph↗