Prof. Tobias Heindel, Department for Quantum Technology, University of Münster

Library, A.2.500, Staudtstr. 2

Location Details

Abstract
Tremendous progress has been achieved in the field of quantum information and photonic quantum technologies. In this context, the generation and precise control of qubits, whether photonic or embedded in the solid-state, lies at the heart of groundbreaking applications holding the potential to transform our society. In this talk, I will review the recent progress in the fields of quantum light generation in the solid-state and implementations of quantum information, ultimately striving towards quantum networking at the global scale [1]. One focus will be on the recent advances in quantum light generation using quantum dot devices based on hybrid circular Bragg gratings (hCBG) enabling high-speed quantum optics experiments at clock-rates well beyond 1 GHz, both at wavelengths around 930 nm [2] and 1550 nm [3]. Using numerically optimized microcavity designs in combination with precise fabrication technologies, high Purcell enhancements can be realized experimentally resulting in ultra-low emitter lifetimes of <30 ps and <80 ps for devices operating at 930 nm and 1550 nm, respectively. Moreover, we report direct fiber-pigtailed hCBG devices featuring excellent quantum optical performance at 930 nm, enabling the generation of fiber-coupled indistinguishable photons at clock-rates > 1 GHz [4]. At 1550 nm even clock-rates of up to 2.5 GHz are achieved for free-space coupled devices with low g(2)(0) < 5% and high photon-indistinguishability > 80%. As a first application, we employ the high-Purcell single-photon sources operating at 930 nm in experiments demonstrating a quantum cryptographic primitive beyond QKD [5], which has important applications in distrustful network settings. More specifically, we experimentally implement a quantum strong coin flipping (QSCF) protocol at 80 MHz clockrate (cf. Fig. 1) and demonstrate an advantage compared to both, classical realizations and implementations using faint laser pulses. We achieve this by employing a fast polarization-state encoding enabling a quantum bit error ratio below 3%, required for the successful execution of this type of protocol. Achieving a quantum coin flipping rate of up to 1.5 kbit/s and a quantum advantage of 1.6%, this work represents an important step forward in exploiting quantum advantages in realistic quantum network settings. Not least, I will highlight the science communication project QuanTour [6], in which a quantum light source, as presented in this talk, travelled across Europe visiting 12 laboratories in 12 countries within 12 months – a true community effort…

[1] D. A. Vajner et al., Advanced Quantum Technologies, 2100116 (2022)
[2] L. Rickert et al., ACS Photonics 12, 464–475 (2025)
[3] R. Behrends et al., manuscript in preparation (2025)
[4] L. Rickert et al., Nanophotonics, doi:10.1515/nanoph-2024-0519 (2025)
[5] D. A. Vajner et al., arXiv:2412.14993 (2024)
[6] QuanTour Website