Bohr's Correspondence Principle and The Area Spectrum of Quantum Black Holes

During the last twenty five years evidence has been mounting that black hole surface area have a discrete spectrum. Moreover, it is widely believed that area eigenvalues are uniformally spaced. There is, however, no general agreement on the spacing of the levels. In this letter we use Bohr's correspondence principle to provide this missing link. We conclude that the area spacing of a black-hole is $4\hbar \ln 3$. This is the unique spacing consistent both with the area-entropy thermodynamic relation for black holes, with Boltzmann-Einstein formula in statistical physics and with Bohr's correspondence principle.