(*
 Copyright (C) 2004-2009 Toby Cubitt

 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; either version 2
 of the License, or (at your option) any later version.

 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.
*)


BeginPackage["Partial`","LinearAlgebra`MatrixManipulation`"]

PartialTranspose::usage =
  "PartialTranspose[p,a,b,sys] gives the partial transpose with respect to
  system sys = (1 or 2) of a density matrix p with subsystems of dimensions
  a and b. Author: Toby Cubitt"

PartialTrace::usage =
  "PartialTrace[p,a,b,sys] gives the partial trace with respect to system
  sys (1 or 2) of a density matrix p with subsystems of dimentions a and b.
  Author: Toby Cubitt"


Begin["`Private`"]

PartialTranspose[p_,a_,b_,sys_]:=Module[{s},
    s=Partition[p,{b,b}];
    s=Transpose[s, If[sys==1,{2,1,3,4},{1,2,4,3}] ];
    s=BlockMatrix[s]
]


PartialTrace[p_,a_,b_,sys_]:=Module[{s},
	s=Partition[p,{b,b}];
	If[sys==2,s=Transpose[s,{3,4,1,2}]];
	s=Tr[s, Plus, 2]
]

End[ ]

EndPackage[ ]