Pilot Reference Free Continuous Variable Quantum Key Distribution with Amplitude Encoding

Continuous-variable quantum key distribution (CVQKD) serves as a vital tool for safeguarding information security. Currently, CVQKD is primarily implemented using a local oscillator. This scheme requires transmitting a high-energy pilot signal as a reference to correct phase drift. However, the pilot signal introduces crosstalk into the quantum signal and complicates digital signal processing. Here we show a pilot-reference-free CVQKD protocol with a local oscillator, where the secret key is encoded on the amplitude of coherent states. The protocol does not require a pilot signal, eliminating pilot-induced crosstalk. We conduct security analysis under collective attacks and simulate its secret key rate. Finally, we perform a proof-of-principle experiment under an optical fiber channel and a free-space channel containing biaxially oriented polypropylene, where the phase of the signal is fully randomized. The protocol remains operable under randomized phase and simplifies physical implementation and digital signal processing, while adapting to optical path fluctuations in complex channels. Continuous variable quantum key distribution with local oscillators typically requires pilot signals to track phase drift. Here, the authors show how to extract keys from signal amplitudes, enabling pilot free operation and proof of principle key generation even when the optical phase is randomised.