  Reference-frame-independent (RFI) quantum key distribution (QKD) presents
promising advantages, especially for mobile-platform-based implementations, as
it eliminates the need for active reference frame calibration. While RFI-QKD
has been explored in various studies, limitations in key rate and distance
persist due to finite data collection. In this study, we experimentally
demonstrate an improved RFI-QKD protocol proposed by Zhu \textit{et al.} [Opt.
Lett. 47, 4219 (2022)], featuring a statistical quantity for bounding
information leaked to Eve that exhibits more insensitivity to statistical
fluctuations and more robustness to variations in the reference frame. Taking
into account finite-size considerations and potential general attacks, RFI-QKD
is implemented over a distance of 175 \si{\kilo\meter} in this work. We believe
that our study extends the communication distance achievable by RFI-QKD,
thereby constituting a notable advancement for its practical application.
