  Topological quantum dots (TQDs) are 3D topological insulator nanoparticles
with radius below 100 nm, which display symmetry-protected surface states with
discretized energies. We propose a scheme which harnesses these energy levels
in a closed lasing scheme, in which a single TQD, when pumped with incoherent
THz light, lases from its surface states in the THz regime. The time scales
associated with the system are unusually slow, and lasing occurs with a very
low threshold. Due to the low threshold, we predict that blackbody radiation at
room-temperature provides enough photons to pump the system, providing a route
to room-temperature THz lasing with blackbody radiation as the pump.
