%0 Journal Article
%T Entanglement witnessing and quantum cryptography with non-ideal ferromagnetic detectors
%A Waldemar K£¿obus
%A Andrzej Grudka
%A Andreas Baumgartner
%A Damian Tomaszewski
%A Christian Sch£¿nenberger
%A Jan Martinek
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevB.89.125404
%X We investigate theoretically the use of non-ideal ferromagnetic contacts as a mean to detect quantum entanglement of electron spins in transport experiments. We use a designated entanglement witness and find a minimal spin polarization of $\eta > 1/\sqrt{3} \approx 58 %$ required to demonstrate spin entanglement. This is significantly less stringent than the ubiquitous tests of Bell's inequality with $\eta > 1/\sqrt[4]{2}\approx 84%$. In addition, we discuss the impact of decoherence and noise on entanglement detection and apply the presented framework to a simple quantum cryptography protocol. Our results are directly applicable to a large variety of experiments.
%U http://arxiv.org/abs/1310.5640v3