  We derive an efficiency bound for continuous quantum heat engines absorbing
heat from squeezed thermal reservoirs. Our approach relies on a full-counting
statistics description of nonequilibrium transport and it is not limited to the
framework of irreversible thermodynamics. Our result, a generalized Carnot
efficiency bound, is valid beyond the small squeezing and high temperature
limit. Our findings are embodied in a prototype three-terminal quantum
photoelectric engine where a qubit converts heat absorbed from a squeezed
thermal reservoir into electrical power. We demonstrate that in the quantum
regime the efficiency can be greatly amplified by squeezing. From the
fluctuation relation we further receive other operational measures in linear
response, for example, the universal maximum power efficiency bound.
