Figure 1

A two-level system (TLS) coupled to cold and hot baths at temperatures $T_{\mathrm{C}}$ and $T_{\mathrm{H}}$, respectively. (a) The cooling cycle where the TLS couples alternately to one of the baths at a time. The interaction of the TLS with each bath is controlled by the level separation: For small (large) splitting it exchanges energy with the cold (hot) bath. The green arrows depict the abrupt expansion (compression). (b) The driving protocol in time, demonstrating one cycle of the process in (a). In a sudden cycle $\delta t\to 0$. (c) Potential experimental realization: the schematic of a superconducting qubit capacitively ($C_c$) coupled to coplanar wave resonators, operating at two distinct frequencies, and terminated by resistors $R_{\mathrm{C}}$ and $R_{\mathrm{H}}$ acting as the heat baths. The energy separation $\mathrm{\Delta }E$ of the TLS is tuned according to the protocol in (a) and (b) by applying magnetic flux $\mathrm{\Phi }$.