# Proposal for distribution of multi-photon entanglement with optimal rate-distance scaling

## TL;DR

This paper introduces a protocol for distributing multi-photon entanglement over long distances using current integrated quantum photonic technology, enabling secure quantum communication and metrology with optimal rate-distance scaling.

## Contribution

It presents a novel scheme utilizing squeezed vacuum states and photon-number-resolving detectors for long-range entanglement distribution with high loss tolerance and optimal rate scaling.

## Key findings

- Achieves near-maximal entanglement distribution over long distances.
- Supports loophole-free Bell tests for certification.
- Provides measurement-device-independent security with potential for full device independence.

## Abstract

We propose a protocol to perform long-range distribution of near-maximally entangled multiphoton states, allowing versatile applications such as quantum key distribution (QKD) and quantum metrology which can provide alternatives to state-of-the-art protocols. Our scheme uses resources available within the current integrated quantum photonic technology: squeezed vacuum states and photon-number-resolving detectors. The distributed entanglement can be certified by Bell tests which have the potential to be loophole free, and may be directly used in well established QKD protocols. Generally, this provides measurement-device-independent (MDI) levels of security, which may be upgraded to fully device-independent (DI) security if the Bell test is loophole-free. In both cases, the protocol is robust to extremely high transmission losses, matching the optimal $O(\sqrt{\eta})$ scaling of key rate with channel transmittance.