  We affirm that the proper momentum defined in [PRL 103:062001 (2009)] does
respect exact gauge symmetry and is as measurable as the kinetic momentum. The
physical part of the gauge field is also as measurable as the electromagnetic
field. The Comment of Ji [arXiv:0910.5022] is due to a misunderstanding of our
work, and a typical confusion of our gauge-invariant formalism with the
specific Coulomb-gauge calculation.
