  The reference-frame-independent quantum key distribution (RFI-QKD) protocol
enables QKD systems to function effectively despite slowly varying reference
frames, offering a distinct advantage in practical scenarios, particularly in
mobile platforms. In this study, we successfully distribute secure key bits
over a 250 km optical fiber distance by developing an RFI-QKD system with a
repetition rate of 150 MHz. Benefiting from high repetition rate, we achieve a
finite-key secret key rate of 49.65 bit/s at a distance of 200 km, which is
more than three times higher than state-of-the-art systems. Our work
dramatically extends the transmission distance and enhances the secret key rate
of RFI-QKD, significantly promoting its practical application.
