maxb.m

该算法是用于量子运算的matlab程序

%   maxb(op) gives maximum value for
%   operators for biseparable states; 
%   considers states with all possible
%   bipartitioning. Calls maxbisep.m.

% Copyright (C) 2005  Geza Toth    E.mail: [e-mail]
%
% 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 mb=maxb(op1)

% Qubits
d=2;

[sx,sy]=size(op1);
N=log2(sx)/log2(d);
N=floor(N+0.5);

% loop for all bipartitioning
mb=0;
for n=1:2^N-2
    list=[];
    b=dec2bin(n+2^N);
    for m=N:-1:1
       if b(m+1)=='1',
           list=[list,m];
       end %if
    end %for 
    if length(list)<=floor(N/2+0.01),
       mb=max(mb,max(eig(maxbisep(op1,list))));
   end %if
end %for