Distribution of GHz sequential Time-bin Entanglement in a Metropolitan Fiber Network

TL;DR

This paper demonstrates the practical distribution of GHz sequential time-bin entangled photon pairs over a 30km fiber network for quantum key distribution, highlighting robustness and high entanglement fidelity.

Contribution

It shows the feasibility of using off-the-shelf components and GHz frequency modulated pulses for high-fidelity entanglement distribution in metropolitan quantum networks.

Findings

Achieved 93% quantum visibility in a 30km fiber link

Used GHz frequency modulated laser pulses for entanglement generation

Distributed high-quality entanglement robust against polarization fluctuations

Abstract

Efficient generation and high-quality distribution of entanglement is becoming increasingly more relevant in the field of quantum technologies, with important applications such as multiparty computation as well as quantum key distribution (QKD) on the rise. Quantum communication protocols based on entanglement offer an inherent quantum based randomness for key generation and provide in general higher security compared to prepare and measure implementations. Moreover, the future quantum internet will also be based on the distribution of entanglement for securely connecting quantum computers in a network. In this work we show the feasibility of using sequential time-bin entangled states for quantum key distribution in metropolitan networks using off-the-shelf components. The time-bin encoding ensures high fidelity distribution robust against random polarisation fluctuations occuring in optical fibers. Modulated laser pulses in the GHz frequency range are used to generate time-bin entangled photon pairs. The entangled photons are then sent over an about 30km long (9.5dB loss) fiber link within the Vienna fiber network, showing high degree of distributed entanglement with a measured 93\% quantum visibility.