Multi-user quantum key distribution with entangled photons from an AlGaAs chip

TL;DR

This paper demonstrates multi-user quantum key distribution using a room-temperature AlGaAs chip that generates entangled photons suitable for integration into existing telecom networks, enabling secure quantum communications.

Contribution

The work introduces a compact, on-chip entangled photon source operating at telecom wavelengths for multi-user QKD without off-chip compensation, advancing practical quantum network deployment.

Findings

Achieved 87% visibility after DWDM separation.

Demonstrated long-distance key distribution over 50 km fiber.

Showcased multi-user QKD with standard telecom components.

Abstract

In view of real world applications of quantum information technologies, the combination of miniature quantum resources with existing fibre networks is a crucial issue. Among such resources, on-chip entangled photon sources play a central role for applications spanning quantum communications, computing and metrology. Here, we use a semiconductor source of entangled photons operating at room temperature in conjunction with standard telecom components to demonstrate multi-user quantum key distribution, a core protocol for securing communications in quantum networks. The source consists of an AlGaAs chip emitting polarization entangled photon pairs over a large bandwidth in the main telecom band around 1550 nm without the use of any off-chip compensation or interferometric scheme; the photon pairs are directly launched into a dense wavelength division multiplexer (DWDM) and secret keys are distributed between several pairs of users communicating through different channels. We achieve a visibility measured after the DWDM of 87% and show long-distance key distribution using a 50-km standard telecom fibre link between two network users. These results illustrate a promising route to practical, resource-efficient implementations adapted to quantum network infrastructures.