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We study a scheme of thermal management where a three-qubit system assisted with a coherent auxiliary bath (CAB) is employed to implement heat management on a target thermal bath (TTB). We consider the CAB/TTB being ensemble of coherent/thermal two-level atoms (TLAs), and within the framework of collision model investigate the characteristics of steady heat current (also called target heat current (THC)) between the system and the TTB. It demonstrates that with the help of the quantum coherence of ancillae the magnitude and direction of heat current can be controlled only by adjusting the coupling strength of system-CAB. Meanwhile, we also show that the influences of quantum coherence of ancillae on the heat current strongly depend on the coupling strength of system—CAB, and the THC becomes positively/negatively correlated with the coherence magnitude of ancillae when the coupling strength below/over some critical value. Besides, the system with the CAB could serve as a multifunctional device integrating the thermal functions of heat amplifier, suppressor, switcher and refrigerator, while with thermal auxiliary bath it can only work as a thermal suppressor. Our work provides a new perspective for the design of multifunctional thermal device utilizing the resource of quantum coherence from the CAB.

We quantify the influence of non-adiabatic leakage and system dissipation on the transfer fidelity with generic counter-intuitive pulses. By including the dissipation of all the parties, we find that the competition between non-adiabaticity and decoherence leads to an upper bound of the transfer fidelity. Using a systematic expansion valid in the desired high-fidelity limit, we derive the upper bound as a simple function of the system cooperativity. This approach also indicates how to reach the upper bound efficiently. Our results are widely applicable to quantum state engineering and are particularly significant for solid-state devices, which typically have non-negligible dissipation of the source and target systems.

In a recent publication (Wang and Clerk 2012 Phys. Rev. Lett. 108 153603), we demonstrated that one can use interference to significantly increase the fidelity of state transfer between two electromagnetic cavities coupled to a common mechanical resonator over a naive sequential-transfer scheme based on two swap operations. This involved making use of a delocalized electromagnetic mode which is decoupled from the mechanical resonator, a so-called ‘mechanically dark’ mode. Here, we demonstrate the existence of a new ‘hybrid’ state transfer scheme that incorporates the best elements of the dark-mode scheme (protection against mechanical dissipation) and the double-swap scheme (fast operation time). Importantly, this new scheme also does not require the mechanical resonator to be prepared initially in its ground state. We also provide additional details of the previously described interference-enhanced transfer schemes, and provide an enhanced discussion of how the interference physics here is intimately related to the optomechanical analogue of electromagnetically induced transparency. We also compare the various transfer schemes over a wide range of relevant experimental parameters, producing a ‘phase diagram’ showing the optimal transfer scheme for different points in parameter space.