Fig. 1. Experimental results.

a Secret key generation rate as a function of the channel loss for the parameters of the implementation. The star represents the achieved generation rate at the field-deployed channel loss. b Long-term stability of the implementation. Each point represents 10 seconds of measurement. While the $\mathcal{Z}$ basis shows great stability over time - an indication of slow phase drift in the fiber—the $\mathcal{X}$ basis shows moments of high QBER due to vibration at the receiver site.