Quantum communication networks rely on quantum cryptographic protocols including quantum key distribution (QKD) using single photons. A critical element regarding the security of QKD protocols is the photon number coherence (PNC), i.e. the phase relation between the zero and one-photon Fock state, which critically depends on the excitation scheme. Thus, to obtain flying qubits with the desired properties, optimal pumping schemes for quantum emitters need to be selected. Semiconductor quantum dots generate on-demand single photons with high purity and indistinguishability. Exploiting two-photon excitation of a quantum dot combined with a stimulation pulse, we demonstrate the generation of high-quality single photons with a controllable degree of PNC. Our approach provides a viable route toward secure communication in quantum networks.
@article{arxiv.2305.20017,
title = {Controlling the Photon Number Coherence of Solid-state Quantum Light Sources for Quantum Cryptography},
author = {Yusuf Karli and Daniel A. Vajner and Florian Kappe and Paul C. A. Hagen and Lena M. Hansen and René Schwarz and Thomas K. Bracht and Christian Schimpf and Saimon F. Covre da Silva and Philip Walther and Armando Rastelli and Vollrath Martin Axt and Juan C. Loredo and Vikas Remesh and Tobias Heindel and Doris E. Reiter and Gregor Weihs},
journal= {arXiv preprint arXiv:2305.20017},
year = {2024}
}