  We compute the entropy of non-extremal black holes using the quantum dynamics
of Loop Gravity. The horizon entropy is finite, scales linearly with the area
A, and reproduces the Bekenstein-Hawking expression S = A/4 with the one-fourth
coefficient for all values of the Immirzi parameter. The near-horizon geometry
of a non-extremal black hole - as seen by a stationary observer - is described
by a Rindler horizon. We introduce the notion of a quantum Rindler horizon in
the framework of Loop Gravity. The system is described by a quantum surface and
the dynamics is generated by the boost Hamiltonion of Lorentzian Spinfoams. We
show that the expectation value of the boost Hamiltonian reproduces the local
horizon energy of Frodden, Ghosh and Perez. We study the coupling of the
geometry of the quantum horizon to a two-level system and show that it
thermalizes to the local Unruh temperature. The derived values of the energy
and the temperature allow one to compute the thermodynamic entropy of the
quantum horizon. The relation with the Spinfoam partition function is
discussed.
