## Classical simulation of quantum-coherent thermal machines. (arXiv:1810.04174v1 [quant-ph])

The performance enhancements observed in various models of continuous quantum
thermal machines have been linked to the buildup of coherences in a preferred
basis. But, is this connection always an evidence of 'quantum-thermodynamic
supremacy'? By force of example, we show that this is not the case. In
particular, we compare a power-driven three-level quantum refrigerator with a
four-level combined cycle, partly driven by power and partly by heat. We focus
on the weak driving regime and find the four-level model to be superior since
it can operate in parameter regimes in which the three-level model cannot, it
may exhibit a larger cooling rate, and, simultaneously, a better coefficient of
performance. Furthermore, we find that the improvement in the cooling rate
matches the increase in the stationary quantum coherences exactly. Crucially,
though, we also show that the thermodynamic variables for both models follow
from a classical representation based on graph theory. This implies that w查看全文