Reduced Density Matrices¶
- ctm.generic_abelian.rdm.open_C2x2_LD(coord, state, env, fusion_level='full', verbosity=0)[source]¶
- Parameters:
coord (tuple(int,int)) – vertex (x,y) for which reduced density matrix is constructed
state (IPEPS_ABELIAN) – underlying wavefunction
env (ENV_ABELIAN) – environment corresponding to
state
fusion_level (str) – controls fusion of indices of open enlarged corner
verbosity (int) – logging verbosity
- Returns:
left-down enlarged corner with open physical indices
- Return type:
yastn.tensor
Computes lower-down enlarged corner centered on vertex
coord
by contracting the following tensor network:s,s' | | / T--a^+a-- | | C--T-----
The physical indices s and s’ of on-site tensor \(a\) at vertex
coord
and its hermitian conjugate \(a^\dagger\) are left uncontractedDepending on fusion_level, the resulting tensor is:
rank-3 : fusion_level= 'full' rank-5 : fusion_level= 'basic' 0 /\ 2 (s,s') 0 1 4 (s,s') | | / | | / T--a^+a--\ T--a^+a--3 | | >--1 | | C--T-----/ C--T-----2
- ctm.generic_abelian.rdm.rdm1x1(coord, state, env, sym_pos_def=False, verbosity=0)[source]¶
- Parameters:
coord (tuple(int,int)) – vertex (x,y) for which reduced density matrix is constructed
state (IPEPS_ABELIAN) – underlying wavefunction
env (ENV_ABELIAN) – environment corresponding to
state
verbosity (int) – logging verbosity
- Returns:
1-site reduced density matrix with indices \(s;s'\)
- Return type:
torch.tensor
Computes 1-site reduced density matrix \(\rho_{1x1}\) centered on vertex
coord
by contracting the following tensor network:C--T-----C | | | T--a^+a--T | | | C--T-----C
where the physical indices s and s’ of on-site tensor \(A\) at vertex
coord
and it’s hermitian conjugate \(A^\dagger\) are left uncontracted
- ctm.generic_abelian.rdm.rdm1x2(coord, state, env, sym_pos_def=False, verbosity=0)[source]¶
- Parameters:
coord (tuple(int,int)) – vertex (x,y) specifies position of 1x2 subsystem
state (IPEPS_ABELIAN) – underlying wavefunction
env (ENV_ABELIAN) – environment corresponding to
state
verbosity (int) – logging verbosity
- Returns:
2-site reduced density matrix with indices \(s_0s_1;s'_0s'_1\)
- Return type:
yastn.tensor
Computes 2-site reduced density matrix \(\rho_{1x2}\) of a vertical 1x2 subsystem using following strategy:
compute four individual corners
construct upper and lower half of the network
contract upper and lower halt to obtain final reduced density matrix
C--T------------------C = C2x2_LU(coord)--------C1x2(coord) | | | | | T--A^+A(coord)--------T C2x2_LD(coord+(0,1))--C1x2(coord+0,1)) | | | T--A^+A(coord+(0,1))--T | | | C--T------------------C
The physical indices s and s’ of on-sites tensors \(A\) (and \(A^\dagger\)) at vertices
coord
,coord+(0,1)
are left uncontracted
- ctm.generic_abelian.rdm.rdm2x1(coord, state, env, sym_pos_def=False, verbosity=0)[source]¶
- Parameters:
coord (tuple(int,int)) – vertex (x,y) specifies position of 2x1 subsystem
state (IPEPS_ABELIAN) – underlying wavefunction
env (ENV_ABELIAN) – environment corresponding to
state
verbosity (int) – logging verbosity
- Returns:
2-site reduced density matrix with indices \(s_0s_1;s'_0s'_1\)
- Return type:
yastn.tensor
Computes 2-site reduced density matrix \(\rho_{2x1}\) of a horizontal 2x1 subsystem using following strategy:
compute four individual corners
construct right and left half of the network
contract right and left halt to obtain final reduced density matrix
C--T------------T------------------C = C2x2_LU(coord)--C2x2(coord+(1,0)) | | | | | | T--A^+A(coord)--A^+A(coord+(1,0))--T C2x1_LD(coord)--C2x1(coord+(1,0)) | | | | C--T------------T------------------C
The physical indices s and s’ of on-sites tensors \(A\) (and \(A^\dagger\)) at vertices
coord
,coord+(1,0)
are left uncontracted
- ctm.generic_abelian.rdm.rdm2x2(coord, state, env, sym_pos_def=False, verbosity=0)[source]¶
- Parameters:
coord (tuple(int,int)) – vertex (x,y) specifies upper left site of 2x2 subsystem
state (IPEPS_ABELIAN) – underlying wavefunction
env (ENV_ABELIAN) – environment corresponding to
state
verbosity (int) – logging verbosity
- Returns:
4-site reduced density matrix with indices \(s_0s_1s_2s_3;s'_0s'_1s'_2s'_3\)
- Return type:
yastn.tensor
Computes 4-site reduced density matrix \(\rho_{2x2}\) of 2x2 subsystem specified by the vertex
coord
of its upper left corner using strategy:compute four individual corners
construct upper and lower half of the network
contract upper and lower half to obtain final reduced density matrix
C--T------------------T------------------C = C2x2_LU(coord)--------C2x2(coord+(1,0)) | | | | | | T--a^+a(coord)--------a^+a(coord+(1,0))--T C2x2_LD(coord+(0,1))--C2x2(coord+(1,1)) | | | | T--a^+a(coord+(0,1))--a^+a(coord+(1,1))--T | | | | C--T------------------T------------------C
The physical indices s and s’ of on-sites tensors \(A\) (and \(A^\dagger\)) at vertices
coord
,coord+(1,0)
,coord+(0,1)
, andcoord+(1,1)
are left uncontracted and given in the same order:s0 s1 s2 s3
- ctm.generic_abelian.rdm.rdm2x2_NNN_1n1(coord, state, env, sym_pos_def=False, verbosity=0)[source]¶
- Parameters:
coord (tuple(int,int)) – vertex (x,y) specifies upper left site of 2x2 subsystem
state (IPEPS_ABELIAN) – underlying wavefunction
env (ENV_ABELIAN) – environment corresponding to
state
verbosity (int) – logging verbosity
- Returns:
2-site reduced density matrix with indices \(s_0s_1;s'_0s'_1\)
- Return type:
torch.tensor
Computes 2-site reduced density matrix \(\rho_{NNN,1n1}\) of two-site subsystem across (1,-1) diagonal specified by the vertex
coord
of its lower left corner using strategy:compute four individual corners
construct upper and lower half of the network
contract upper and lower half to obtain final reduced density matrix
C--T------------------T------------------C = C2x2_LU(coord+(0,-1))-C2x2(coord+(1,-1)) | | | | | | T--A^+A(coord+(0,-1))-A^+A(coord+(1,-1))-T C2x2_LD(coord)--------C2x2(coord+(1,0)) | | | | T--A^+A(coord)--------A^+A(coord+(1,0))--T | | | | C--T------------------T------------------C
The physical indices s and s’ of on-sites tensors \(A\) (and \(A^\dagger\)) at vertices
coord
andcoord+(1,-1)
are left uncontracted and given in the same order:x s1 s0 x