On a Monolithic Silicon Integration Approach for QKD

Ramona Wolf

Florian Honz, W. Boxleitner, Mariana F. Ramos +4 more

Quantum key distribution (QKD) allows the secure transmission of encryption keys in the dawning age of quantum computers. However, despite photonic integration efforts, the size and complexity of current QKD systems remains a roadblock for practical deployment in cost-sensitive applications. Here we show a monolithic integrated QKD transmitter that exclusively builds on silicon photonics. We introduce a germanium-on-silicon light emitter acting as source for a co-integrated quantum state encoder, to generate a secure key over a 45.9 km field-installed fiber link. On top of this, we demonstrate the broadband operation of our QKD transmitter by generating keys over 32 wavelength channels, making it an integrated colorless QKD transmitter with full C-band coverage. Employing monolithic silicon technology paves the way towards fully integrated optoelectronic QKD transmitters, enabling a drastic reduction of size and cost while benefiting from the maturity and mass production capabilities of complementary metal–oxide semiconductor (CMOS) technology. Moreover, omitting the need for rare and costly III-V semiconductor materials to generate light can drastically reduce the overburdening assembly and packaging requirements inherent to optoelectronics, potentially enabling QKD to finally enter new application domains closer to the consumer market.

Denis Fatkhiev, João dos Reis Frazão, Alireza H. Derkani +4 more

We demonstrate the first CV-QKD system featuring a custom-designed monolithic silicon photonic dual-polarisation transceiver. Leveraging PS-64-QAM, we achieved 1.9 Mbit/s secret key rate across 25 km of standard single-mode fibre, highlighting the potential of electronic-photonic integration for practical QKD.

Ryan M. Camacho, Ian W. Frank, Matthew Tomes +3 more

Denis M. Fatkhiev, João Frazão, Alireza H. Derkani +4 more

Continuous-variable quantum key distribution (CVQKD) is a promising technology for enabling quantum-secure networks, valued for its compatibility with conventional telecommunication hardware and maturing security proofs. Although the need for quantum-safe infrastructure is driven by the threat of advancing quantum computing, the widespread deployment of QKD remains elusive because current discrete-component solutions suffer from high cost, high energy consumption, and lack of conformity with the existing telecom network infrastructure. In this work, we demonstrate a compact CV-QKD system based on a custom-designed, monolithically integrated silicon photonic dualpolarization transceiver, operated with an off-chip seed laser. Taking into account the block length of 2 × 107 and employing 64-quadrature amplitude modulation (QAM) shaped probabilistically, our system achieves a secret key rate of 1.9 Mbit/s in 25km of standard single-mode fiber. This work highlights the significant potential of electronic-photonic integration to advance the practical deployment of QKD networks.

M. Mondin, F. Daneshgaran, Francesco Di Stasio +11 more