Field demonstration of a self-contained 10 km mobile-to-ground quantum network node via common-aperture co-propagation
In this work, we demonstrate a dual-function, common-aperture free-space optical system that simultaneously supports decoy-state BB84 quantum key distribution (QKD) at 803 nm and bidirectional classical laser communication at 640/660 nm over a 10.31 km terrestrial link from a mobile platform to a stationary ground station. To the best of our knowledge, this is the first field demonstration of a fully integrated common-aperture architecture where a co-propagating classical optical link simultaneously performs full QKD post-processing and ecrypted payload transmission over a 10 km atmospheric channel. The classical link utilizes Manchester-coded on-off keying (MC-OOK) at 10 MHz, achieving a packet error rate of $\sim$ 0.4 $\%$ (estimated bit error rate (BER) of 3.13 $\times$ 10$^{-5}$) with hardware-based self-synchronization and error-packet retransmission. Over the 10.31 km link, the QKD system achieved an average quantum bit error rate (QBER) of 2.512 $\%$ and an average secret key rate of 644 bps using rate-adaptive low-density parity-check (LDPC) codes. Finally, using the distilled keys, real-time AES-256 encrypted image transmission was executed over the co-aligned classical optical channel, proving the feasibility of a completely self-contained, jam resistant mobile quantum optical network.