By harnessing the unique high-speed property of the optical waveguide-integrated SNSPD, the dead time of single-photon detection is reduced by more than an order of magnitude compared to the traditional normal-incidence SNSPD. This therefore allowed the team to resolve one of the long-standing challenges in quantum optics: optimal Bell-state measurement of time-bin encoded qubits.
The advancement is important not just for quantum optics, but also for quantum communications, from an applications perspective. The team employed the advantages of the heterogeneously integrated, superconducting silicon-photonic platform to realize a server for measurement-device-independent quantum key distribution (MDI-QKD).
This effectively removed all possible detector side-channel attacks, which in turn enhances the security of quantum cryptography.
Combined with a time multiplex technique, the method obtains an order of magnitude increase in MDI-QKD key rate.
“In contrast with GHz clock rate MDI-QKD experiments, our system does not require a complicated injection locking technique, which significantly reduces the complexity of the transmitter,” said Xiaodong Zheng, from the group of Xiao-Song Ma of Nanjing University and first author of the paper.
“This work shows that integrated quantum-photonic chips provide not only a route to miniaturization, but also significantly enhance the system performance compared to traditional platforms,” Ma said. “Combined with integrated QKD transmitters, a fully chip-based, scalable, and high-key-rate metropolitan quantum network should be realized in the near future.”
The research was published in Advanced Photonics (www.doi.org/10.1117/1.AP.3.5.055002).
