  Device-independent quantum key distribution does not need a precise quantum
mechanical model of employed devices to guarantee security. Despite of its
beauty, it is still a very challenging experimental task. We compare a recent
proposal by Gisin et al. [Phys. Rev. Lett. 105, 070501 (2010)] to close the
detection loophole problem with that of a simpler quantum relay based on
entanglement swapping with linear optics. Our full-mode analysis for both
schemes confirms that, in contrast to recent beliefs, the second scheme can
indeed provide a positive key rate which is even considerably higher than that
of the first alternative. The resulting key rates and required detection
efficiencies of approx. 95% for both schemes, however, strongly depend on the
underlying security proof.
