FermionSite
full name: tenpy.networks.site.FermionSite
parent module:
tenpy.networks.site
type: class
Inheritance Diagram
Methods
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Add one on-site operators. |
|
Change the charges of the site (in place). |
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Convert charge values to Jordan-Wigner parity. |
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Load instance from a HDF5 file. |
Return the hermitian conjugate of a given operator. |
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Return operator of given name. |
Multiply operator names together. |
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Multiply local operators (possibly given by their names) together. |
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Whether an (composite) onsite operator is fermionic and needs a Jordan-Wigner string. |
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Remove an added operator. |
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Rename an added operator. |
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Export self into a HDF5 file. |
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Sort the |
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Return index of a basis state from its label. |
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Same as |
Sanity check, raises ValueErrors, if something is wrong. |
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Check whether 'name' labels a valid onsite-operator. |
Class Attributes and Properties
Dimension of the local Hilbert space. |
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Dictionary of on-site operators for iteration. |
- class tenpy.networks.site.FermionSite(conserve='N', filling=0.5)[source]
Bases:
Site
Create a
Site
for spin-less fermions.Local states are
empty
andfull
.Warning
Using the Jordan-Wigner string (
JW
) is crucial to get correct results, otherwise you just describe hardcore bosons! Further details in Fermions and the Jordan-Wigner transformation.operator
description
Id
Identity \(\mathbb{1}\)
JW
Sign for the Jordan-Wigner string.
C
Annihilation operator \(c\) (up to ‘JW’-string left of it)
Cd
Creation operator \(c^\dagger\) (up to ‘JW’-string left of it)
N
Number operator \(n= c^\dagger c\)
dN
\(\delta n := n - filling\)
dNdN
\((\delta n)^2\)
conserve
qmod
excluded onsite operators
'N'
[1]
–
'parity'
[2]
–
'None'
[]
–
- Parameters:
- add_op(name, op, need_JW=False, hc=None, permute_dense=None)[source]
Add one on-site operators.
- Parameters:
name (str) – A valid python variable name, used to label the operator. The name under which op is added as attribute to self.
op (np.ndarray |
Array
) – A matrix acting on the local hilbert space representing the local operator. Dense numpy arrays are automatically converted toArray
. LegCharges have to be[leg, leg.conj()]
. We set labels'p', 'p*'
.need_JW (bool) – Whether the operator needs a Jordan-Wigner string. If
True
, add name toneed_JW_string
.hc (None | False | str) – The name for the hermitian conjugate operator, to be used for
hc_ops
. By default (None
), try to auto-determine it. IfFalse
, disable adding entries tohc_ops
.permute_dense (bool | None) – Flag to enable/disable permutations when converting op from numpy to np_conserved arrays. If True, the operator is permuted with
perm
to account for permutations induced by sorting charges; False disables the permutations. By default (None
), the value ofused_sort_charge
is used.
- change_charge(new_leg_charge=None, permute=None)[source]
Change the charges of the site (in place).
- Parameters:
new_leg_charge (
LegCharge
| None) – The new charges to be used. IfNone
, use trivial charges.permute (ndarray | None) – The permutation applied to the physical leg, which also gets used to adjust
state_labels
andperm
. If you sorted the previous leg withperm_qind, new_leg_charge = leg.sort()
, useold_leg.perm_flat_from_perm_qind(perm_qind)
. Ignored ifNone
.
- charge_to_JW_signs(charges)[source]
Convert charge values to Jordan-Wigner parity.
Often, charge conservation contains the (parity of) the total fermion number. This information is enough to lift a Jordan-Wigner string applied on the left of a given bond to the virtual leg of an MPS: given the total parity number of fermions
parity[alpha] = N_fermions[alpha] % 2
in each Schmidt state|alpha>
, simply send|alpha> --> (-1)**parity[alpha] |alpha>
. Given the charges values of the Schmidt states|alpha>
, this function returns the corresponding(-1)**parity
Jordan-Wigner signs.- Parameters:
charges (2D or 1D array) – Charge values, last dimension is len
chinfo.qnumber
. We choose the convention that these charge values correspond to an “incoming” leg withqconj=+1
.- Returns:
Should only have values +1 or -1.
- Return type:
JW_signs
- property dim
Dimension of the local Hilbert space.
- classmethod from_hdf5(hdf5_loader, h5gr, subpath)[source]
Load instance from a HDF5 file.
This method reconstructs a class instance from the data saved with
save_hdf5()
.- Parameters:
hdf5_loader (
Hdf5Loader
) – Instance of the loading engine.h5gr (
Group
) – HDF5 group which is represent the object to be constructed.subpath (str) – The name of h5gr with a
'/'
in the end.
- Returns:
obj – Newly generated class instance containing the required data.
- Return type:
cls
- get_op(name)[source]
Return operator of given name.
- Parameters:
name (str) – The name of the operator to be returned. In case of multiple operator names separated by whitespace, we multiply them together to a single on-site operator (with the one on the right acting first).
- Returns:
op – The operator given by name, with labels
'p', 'p*'
. If name already was an npc Array, it’s directly returned.- Return type:
- multiply_op_names(names)[source]
Multiply operator names together.
Join the operator names in names such that get_op returns the product of the corresponding operators.
- multiply_operators(operators)[source]
Multiply local operators (possibly given by their names) together.
- Parameters:
operators (list of {str |
Array
}) – List of valid operator names (to be translated withget_op()
) or directly on-site operators in the form of npc arrays with'p', 'p*'
label. The operators are multiplied left-to-right.- Returns:
combined_operator – The product of the given operators in a left-to-right multiplication following the usual mathematical convention. For example, if
operators=['Sz', 'Sp', 'Sx']
, the final operator is equivalent tosite.get_op('Sz Sp Sx')
, with the'Sx'
operator acting first on any physical state.- Return type:
- property onsite_ops
Dictionary of on-site operators for iteration.
Single operators are accessible as attributes.
- op_needs_JW(name)[source]
Whether an (composite) onsite operator is fermionic and needs a Jordan-Wigner string.
- remove_op(name)[source]
Remove an added operator.
- Parameters:
name (str) – The name of the operator to be removed.
- save_hdf5(hdf5_saver, h5gr, subpath)[source]
Export self into a HDF5 file.
This method saves all the data it needs to reconstruct self with
from_hdf5()
.This implementation saves the content of
__dict__
withsave_dict_content()
, storing the format under the attribute'format'
.
- sort_charge(bunch=True)[source]
Sort the
leg
charges (in place).- Parameters:
bunch (bool) – Whether to also group equal charges into larger blocks (usually a good idea).
- Returns:
perm – The permutation
- Return type:
1D ndarray
- state_indices(labels)[source]
Same as
state_index()
, but for multiple labels.