  We investigate theoretically a refrigerator based on a two-level system (TLS)
coupled alternately to two different heat baths. Modulation of the coupling is
achieved by tuning the level spacing of the TLS. We find that the TLS, which
avoids quantum coherences, creates finite cooling power for one of the baths in
sudden cycles, i.e. acts as a refrigerator even in the limit of infinite
operation frequency. By contrast, the cycles that create quantum coherence in
the sudden expansions and compressions lead to heating of both the baths. We
propose a driving method that avoids creating coherence and thus restores the
cooling in this system. We also discuss a physical realization of the cycle
based on a superconducting qubit coupled to dissipative LC-resonators.

Quantum Physics;Mesoscale and Nanoscale Physics