Continuous-Variable Quantum Key Distribution with a Real Local Oscillator and without Auxiliary Signals
This work addresses the problem of making CV-QKD more cost-efficient and widely implementable for secure communication systems by eliminating the need for remote local oscillators or auxiliary signals, representing a potential third generation of CV-QKD systems.
The paper tackled the challenge of mitigating laser phase noise in continuous-variable quantum key distribution (CV-QKD) at low signal-to-noise ratios, and experimentally demonstrated for the first time that CV-QKD can be performed with a real local oscillator and without auxiliary signals using machine learning methods, achieving a key rate of 9.2 Mbit/s over 26 km at a quantum channel signal-to-noise ratio of -19.1 dB.
Continuous-variable quantum key distribution (CV-QKD) is realized with coherent detection and is therefore very suitable for a cost-efficient implementation. The major challenge in CV-QKD is mitigation of laser phase noise at a signal to noise ratio of much less than 0 dB. So far, this has been achieved with a remote local oscillator or with auxiliary signals. For the first time, we experimentally demonstrate that CV-QKD can be performed with a real local oscillator and without auxiliary signals which is achieved by applying Machine Learning methods. It is shown that, with the most established discrete modulation protocol, the experimental system works down to a quantum channel signal to noise ratio of -19.1 dB. The performance of the experimental system allows CV-QKD at a key rate of 9.2 Mbit/s over a fiber distance of 26 km. After remote local oscillator and auxiliary signal aided CV-QKD, this could mark a starting point for a third generation of CV-QKD systems that are even more attractive for a wide implementation because they are almost identical to standard coherent systems.