High-rate intercity quantum key distribution with a semiconductor single-photon source

Abstract

Quantum key distribution (QKD) enables the transmission of information that is secure against general attacks by eavesdroppers. The use of on-demand quantum light sources in QKD protocols is expected to help improve security and maximum tolerable loss. Semiconductor quantum dots (QDs) are a promising building block for quantum communication applications because of the deterministic emission of single photons with high brightness and low multiphoton contribution. Here we report on the first intercity QKD experiment using a bright deterministic single photon source. A BB84 protocol based on polarisation encoding is realised using the high-rate single photons in the telecommunication C-band emitted from a semiconductor QD embedded in a circular Bragg grating structure. Utilising the 79 km long link with 25.49 dB loss (equivalent to 130 km for the direct-connected optical fibre) between the German cities of Hannover and Braunschweig, a record-high secret key bits per pulse of 4.8 * 10^{-5} with an average quantum bit error ratio of ~ 0.65 % are demonstrated. An asymptotic maximum tolerable loss of 28.11 dB is found, corresponding to a length of 144 km of standard telecommunication fibre. Deterministic semiconductor sources therefore challenge state-of-the-art QKD protocols and have the potential to excel in measurement device independent protocols and quantum repeater applications.

10 pages, 4 figures

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• Secure Quantum Key Distribution Using a Room-Temperature Quantum Emitter
• Entanglement-verified time distribution in a metropolitan network
• Indistinguishable Single Photons from Nanowire Quantum Dots in the Telecom O-Band
• Decoy-state quantum key distribution over 227 km with a frequency-converted telecom single-photon source
• A global quantum network with ground-based single-atom memories in optical cavities and satellite links
• $CdT{e}_{0.25}S{e}_{0.75}$ Quantum Dots as Efficient Room Temperature Single Photon Source for Quantum Technology
• Ultrastable, low-error dynamic polarization encoding of deterministically generated single photons
• Source-independent quantum key distribution without pre-sending entanglement
• Mechanisms and Opportunities for Tunable High-Purity Single Photon Emitters: A Review of Hybrid Perovskites and Prospects for Bright Squeezed Vacuum