  Quantum heat engines and quantum refrigerators are proposed in three-terminal
quantum Hall (QH) and quantum spin Hall (QSH) setups with a voltage-temperature
probe in linear and nonlinear transport regimes. In the linear response regime,
we find that efficiency at maximum power approaches the Curzon-Ahlborn limit in
both QH and QSH setups. Similarly, in nonlinear response, we find that
efficiency at maximum power reaches the Whitney bounds. For the first time, we
see that the thermoelectric efficiency limits in linear and nonlinear transport
regimes are achieved using quantum point contacts in the same setup.
