Continuous-Variable Quantum Key Distribution over 15 km Multi-Core Fiber

The secure transfer of information is critical for the ever-increasing demands of the digital world. Continuous-variable quantum key distribution (CV-QKD) is a technology that can potentially provide information-theoretic security to cryptographic systems. CV-QKD is highly attractive thanks to high secret key rate generation over metropolitan distances and integration with the current classical communication networks. Here we demonstrate CV-QKD across a 15 km multi-core fiber (MCF) where we take advantage of one core to remotely frequency lock Bob's local oscillator with Alice's transmitter. We also demonstrate the capacity of the MCF to boost the secret key rate by parallelizing CV-QKD across multiple cores. Our results point out that MCFs are promising for metropolitan deployment of QKD systems