Karol Horodecki Michal Horodecki Pawel Horodecki Jonathan Oppenheim General Paradigm for Distilling Classical Key From Quantum States. 1898-1929 2009 55 IEEE Transactions on Information Theory 4 http://dx.doi.org/10.1109/TIT.2008.2009798 db/journals/tit/tit55.html#HorodeckiHHO09