  The quantum mechanics of Rotating, Charged, de Sitter and String Theory black
holes are of recent interest because of their peculiar thermodynamic
properties, as well the mysterious nature of their microstates. A full quantum
treatment of the operators involved in this systems could yield valuable
information into their nature, similar to how quantum treatment yields valuable
insight into atoms, molecules and elementary particles. We study four types of
black holes using quantum computing, which include the 3D Rotating
Banados-Teitelboim-Zanelli (BTZ) black hole, the 4D charged Reisner-Nordtrom
(RN) black hole, the 4D charged Reisner-Nordstrom -de Sitter (RN-dS) black hole
and the 2D charged string black hole. In these cases in addition to the
Hamiltonian there is a Mass operator which plays an important role in
describing the quantum states of the black hole. We compute the spectrum of
these operators using classical and quantum computing. For quantum computing we
use the Variational Quantum Eigensolver (VQE) which is hybrid classical-quantum
algorithm that runs on near term quantum hardware. We perform our calculations
using 4 qubits in both a harmonic oscillator and position basis, realizing the
quantum operators of the black holes in terms of 16 x 16 matrices. For the 4
qubit case we find highly accurate results for the Mass eigenvalues for
different values of the charge and angular momentum. For the 2D Charged String
black hole we also use the VQE to compute the expectation value of the
Hamiltonian constraint and the commutator of the Hamiltonian constraint with
the mass operator and find excellent agreement with theoretical expectations.
