% realign   Realignment of the bipartite density matrix.%    realign(M) realigns the matrix M (that can be a density matrix)%    in a bipartite system where the two parties have equal dimensions.%    If the trace norm of the realigned density matrix is larger than 1%    then the state is entangled. For more details see %    O. Rudoplh, Phys. Rev. A 67, 032312 (2003).% Copyright (C) 2006-2007  Geza Toth    E.mail: toth@alumni.nd.edu%% This program is free software; you can redistribute it and/or% modify it under the terms of the GNU General Public License% as published by the Free Software Foundation; see gpl.txt% of this subroutine package.%% This program is distributed in the hope that it will be useful,% but WITHOUT ANY WARRANTY; without even the implied warranty of% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the% GNU General Public License for more details.% % You should have received a copy of the GNU General Public License% along with this program; if not, write to the Free Software% Foundation, Inc., 51 Franklin Street, Fifth Floor, % Boston, MA  02110-1301, USA.function rhoR=realign(rho)[sy,sx]=size(rho);d=floor(sqrt(sy)+0.5);rhoR=mrealign(rho,[4 2 3 1],d);