# Overcoming lossy channel bounds using a single quantum repeater node

**Part of the following topical collections:**

## Abstract

We propose a scheme for performing quantum key distribution (QKD) which has the potential to beat schemes based on the direct transmission of photons between the communicating parties. In our proposal, the communicating parties exchange photons with two quantum memories placed between them. This is a very simple quantum repeater scheme and can be implemented with currently available technology. Ideally, its secret key rate scales as the square root of the transmittivity of the optical channel, which is superior to QKD schemes based on direct transmission because key rates for the latter scale at best linearly with transmittivity. Taking into account various imperfections in each component of our setup, we present parameter regimes in which our protocol outperforms protocols based on direct transmission.

## Keywords

Direct Transmission Optical Channel Quantum Memory Bell State Measurement Dark Count## Notes

### Acknowledgments

We would like to thank Mohsen Razavi for insightful discussions, including a hint regarding the relevance of the high-loss limit to quantum networks. We also thank Ryo Namiki for many fruitful discussions. This work has been supported by an NSERC Discovery Grant, the DARPA QUINESS program, and Industry Canada.

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