  We address multi-parameter quantum estimation for one-dimensional
discrete-time quantum walks and its applications to quantum metrology. We use
the quantum walker as a probe for unknown parameters encoded on its coin
degrees of freedom. We find an analytic expression of the quantum Fisher
information matrix for the most general coin operator, and show that only two
out of the three coin parameters can be accessed. We also prove that the
resulting two-parameter coin model is asymptotically classical i.e. the Uhlmann
curvature vanishes. Finally, we apply our findings to relevant case studies,
including the simultaneous estimation of charge and mass in the discretized
Dirac model.
