  We theoretically investigate a quantum dot coupled to fermionic (electronic)
leads and show how zero-point quantum fluctuations stemming from bosonic
environments permit the rectification of the current. The bosonic baths are
either external impedances modeled as tunable transmission lines or LC
resonators (single-mode cavities). Voltage fluctuations stemming from the
external impedances at zero temperature are described through harmonic
oscillators (photon-like excitations) then producing the quantum vacuum
fluctuations. The differing sizes of the zero-point fluctuations of the quantum
vacuum break the spatial symmetry of the system if the quantum dot is coupled
to two reservoirs or two junctions with different bosonic environments. We
consider current rectification and power production when the system is operated
as a heat engine in both non-resonant and resonant sequential tunneling cases.
