SpinHalfSite

• full name: tenpy.networks.site.SpinHalfSite

• parent module: tenpy.networks.site

• type: class

class tenpy.networks.site.SpinHalfSite(conserve='Sz')

Bases: tenpy.networks.site.Site

Spin-1/2 site.

Local states are up (0) and down (1). Local operators are the usual spin-1/2 operators, e.g. Sz = [[0.5, 0.], [0., -0.5]], Sx = 0.5*sigma_x for the Pauli matrix sigma_x.

operator	description
Id, JW	Identity \(\mathbb{1}\)
Sx, Sy, Sz	Spin components \(S^{x,y,z}\), equal to half the Pauli matrices.
Sigmax, Sigmay, Sigmaz	Pauli matrices \(\sigma^{x,y,z}\)
Sp, Sm	Spin flips \(S^{\pm} = S^{x} \pm i S^{y}\)

conserve	qmod	excluded onsite operators
'Sz'	[1]	Sx, Sy, Sigmax, Sigmay
'parity'	[2]	–
None	[]	–

Parameters

conservestr

Defines what is conserved, see table above.

Attributes

conservestr

Defines what is conserved, see table above.

Methods

add_op(self, name, op[, need_JW])	Add one on-site operators.
change_charge(self[, new_leg_charge, permute])	Change the charges of the site (in place).
get_op(self, name)	Return operator of given name.
multiply_op_names(self, names)	Multiply operator names together.
op_needs_JW(self, name)	Whether an (composite) onsite operator is fermionic and needs a Jordan-Wigner string.
remove_op(self, name)	Remove an added operator.
rename_op(self, old_name, new_name)	Rename an added operator.
state_index(self, label)	Return index of a basis state from its label.
state_indices(self, labels)	Same as state_index(), but for multiple labels.
test_sanity(self)	Sanity check, raises ValueErrors, if something is wrong.
valid_opname(self, name)	Check whether ‘name’ labels a valid onsite-operator.

add_op(self, name, op, need_JW=False)

Add one on-site operators.

Parameters

namestr

A valid python variable name, used to label the operator. The name under which op is added as attribute to self.

opnp.ndarray | Array

A matrix acting on the local hilbert space representing the local operator. Dense numpy arrays are automatically converted to Array. LegCharges have to be [leg, leg.conj()]. We set labels 'p', 'p*'.

need_JWbool

Whether the operator needs a Jordan-Wigner string. If True, the function adds name to need_JW_string.

change_charge(self, new_leg_charge=None, permute=None)

Change the charges of the site (in place).

Parameters

new_leg_chargeLegCharge | None

The new charges to be used. If None, use trivial charges.

permutendarray | None

The permuation applied to the physical leg, which gets used to adjust state_labels and perm. If you sorted the previous leg with perm_qind, new_leg_charge = leg.sort(), use leg.perm_flat_from_perm_qind(perm_qind). Ignored if None.

property dim

Dimension of the local Hilbert space.

get_op(self, name)

Return operator of given name.

Parameters

namestr

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

opnp_conserved

The operator given by name, with labels 'p', 'p*'. If name already was an npc Array, it’s directly returned.

multiply_op_names(self, names)

Multiply operator names together.

Join the operator names in names such that get_op returns the product of the corresponding operators.

Parameters

nameslist of str

List of valid operator labels.

Returns

combined_opnamestr

A valid operator name Operatorname representing the product of operators in names.

property onsite_ops

Dictionary of on-site operators for iteration.

Single operators are accessible as attributes.

op_needs_JW(self, name)

Whether an (composite) onsite operator is fermionic and needs a Jordan-Wigner string.

Parameters

namestr

The name of the operator, as in get_op().

Returns

needs_JWbool

Whether the operator needs a Jordan-Wigner string, judging from need_JW_string.

remove_op(self, name)

Remove an added operator.

Parameters

namestr

The name of the operator to be removed.

rename_op(self, old_name, new_name)

Rename an added operator.

Parameters

old_namestr

The old name of the operator.

new_namestr

The new name of the operator.

state_index(self, label)

Return index of a basis state from its label.

Parameters

labelint | string

eather the index directly or a label (string) set before.

Returns

state_indexint

the index of the basis state associated with the label.

state_indices(self, labels)

Same as state_index(), but for multiple labels.

test_sanity(self)

Sanity check, raises ValueErrors, if something is wrong.

valid_opname(self, name)

Check whether ‘name’ labels a valid onsite-operator.

Parameters

namestr

Label for the operator. Can be multiple operator(labels) separated by whitespace, indicating that they should be multiplied together.

Returns

validbool

True if name is a valid argument to get_op().