Telecom Optoelectronics with 92% Interference Visibility in the C-Band

Quantum Dot Photon Source Telecom Optoelectronics with 92% Interference Visibility in the C-Band

2026-02-04 From Hendrik Härter | Translated by AI 2 min Reading Time

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An optoelectronic light source that generates single photons on demand in the telecommunications C-band with record quality has an interference visibility of 92 percent. This is an important step towards scalable photonic quantum computing and quantum communication.

View of the quantum optics laboratory at the University of Stuttgart: here, researchers are experimenting with new photon sources for quantum computing and quantum networks.(Image: Barz Group, University of Stuttgart) — View of the quantum optics laboratory at the University of Stuttgart: here, researchers are experimenting with new photon sources for quantum computing and quantum networks.
(Image: Barz Group, University of Stuttgart)

A research team from the University of Stuttgart and the Julius-Maximilians-Universität Würzburg led by Prof. Stefanie Barz (University of Stuttgart) has realized an optoelectronic light source that generates single photons in the C-band (1,550 nm), which is critical for telecommunications, with record quality and deterministically. With a two-photon interference visibility of almost 92 percent, the quantum dot device achieves values that are competitive with probabilistic systems for the first time, while at the same time operating deterministically.

"The fact that no high-quality C-band photon source was available that works deterministically was a central problem in quantum optics laboratories for over a decade. Our new technology now removes this obstacle," explains Prof. Stefanie Barz. This means access to synchronizable photon sources for the telecommunications band for the first time.

Deterministic Photon Generation

Nico Hauser (1st from left) and other scientists from the Barz Group.(Image: Barz Group, University of Stuttgart) — Nico Hauser (1st from left) and other scientists from the Barz Group.
(Image: Barz Group, University of Stuttgart)

Unlike conventional probabilistic methods such as spontaneous parametric downconversion (SPDC), the new quantum dot-based source generates photons exactly when it is electronically controlled. This property is essential for the synchronization of multiple photon sources in complex optoelectronic systems.

The high indistinguishability of the generated photons is a critical parameter for quantum interference applications and enables precise control over interference effects. These controlled quantum effects are a basic requirement for advanced applications in the field of quantum computing and quantum communication.

Integration in Telecommunications Infrastructure

Compatibility with existing fiber optic infrastructure is crucial for the industrial implementation of photonic quantum technologies. The telecommunications C-band around 1,550 nm offers minimal optical losses in standard single-mode fibers and is therefore the industrial standard for long-distance data transmission.

Previous quantum dot photon sources achieved their best properties at shorter wavelengths of 780 to 960 nm, while C-band implementations achieved at best 72 percent interference visibility. This is well below the requirements of demanding quantum applications.

The developed device is based on indium arsenide quantum dots in an indium aluminum gallium arsenide matrix, integrated into a circular Bragg grating resonator to amplify the photon emission.

The core parameters include:

Wavelength: C-band (≈1,550 nm)
Operating mode: Deterministic (on-demand)
Two-photon interference visibility: 92 percent
Excitation: Phonon-mediated (optimized crystal lattice vibrations)

The team systematically compared different excitation schemes and identified phonon-mediated excitation as optimal compared to direct optical pumping with higher-energy light.

Possible Application Perspectives

The combination of deterministic generation, C-band compatibility and high photon quality opens up new possibilities:

Quantum communication hardware for telecommunications networks,
High-precision optical measurement technology and
Quantum cryptography modules.

The medium-term developments include

Photonic quantum processors for distributed computing architectures
Quantum repeater for long-range quantum communication
Hybrid optical-electronic systems

The publication is the result of cooperation between Stuttgart (system integration) and Würzburg (quantum dot production under Prof. Sven Höfling). The development is part of the BMFTR-funded PhotonQ project, which is realizing a photonic quantum processor at the University of Stuttgart.

The successor project Quantumrepeater.Net (QR.N) aims to network several photonic processors for distributed quantum computing - a technology with considerable potential for the future electronics and IT industry. (heh)

Link: Deterministic and highly indistinguishable single photons in the telecom C-band. Nature Communications. Retrieved on 2.2.2026.

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