Quantum key distribution (QKD) is a quantum communication technology that promises unconditional communication security. High-performance and cost-effective QKD systems are essential for the establishment of quantum communication networks1–3. By integrating all the optical components (except the laser source) on a silicon photonic chip, we have realized a stable, miniaturized and low-cost system for continuous-variable QKD (CV-QKD) that is compatible with the existing fibre optical communication infrastructure4. Here, the integrated silicon photonic chip is demonstrated for CV-QKD. It implements the widely studied Gaussian-modulated coherent state protocol that encodes continuous distributed information on the quadrature of laser light5,6. Our proof-of-principle chip-based CV-QKD system is capable of producing a secret key rate of 0.14 kbps (under collective attack) over a simulated distance of 100 km in fibre, offering new possibilities for low-cost, scalable and portable quantum networks. A sender and a receiver for continuous-variable quantum key distribution are packed onto separate silicon photonic chips. By using an external 1,550-nm laser, a secret key rate of 0.14 kbps is transmitted over a simulated distance of 100 km in fibre.

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Quantum optics: Single-photon detectors

An integrated silicon photonic chip platform for continuous-variable quantum key distribution

We report the fabrication of a superconducting nanowire single-photon detector (SSPD or SNSPD) with an ultralow dark count rate. By introducing optical band-pass filters at the input of the SSPD and cooling the filters at 3 K, the dark count rate is reduced to less than 1/100 at low bias. An SSPD with 0.1 cps dark count rate and 5.6% system detection efficiency at 1550 nm wavelength is obtained. We show that a quantum key distribution (QKD) over 300 km of fiber is possible based on a numerical calculation assuming a differential phase shift QKD protocol implemented with our SSPDs.

https://iopscience.iop.org/article/10.7567/APEX.6.072801/pdf

Quantum optics: Single-photon detectors

Citations

An integrated silicon photonic chip platform for continuous-variable quantum key distribution

References

Superconducting Nanowire Single-Photon Detector with Ultralow Dark Count Rate Using Cold Optical Filters

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