Irregular lattice site removing doubt

How do I use this algorithm? What does that parameter do?
amankumar
Posts: 17
Joined: 17 Apr 2020, 11:14

Irregular lattice site removing doubt

In the new released you updated the Irregular lattice site where one can remove some sites. I read the documentation but did not understood how to specify the sites which one wants to remove. I considered Toric code model(L_x=3,L_y=3) and wanted to remove all sites(18,19,20,21,22,23) which are not shown in Image of Dual square lattice. Below I am writing the interaction term which code provides.

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1.00000 * Sigmaz_0 Sigmaz_3 Sigmaz_4 Sigmaz_6 +
1.00000 * Sigmaz_1 Sigmaz_4 Sigmaz_5 Sigmaz_7 +
1.00000 * Sigmaz_2 Sigmaz_3 Sigmaz_5 Sigmaz_8 +
1.00000 * Sigmax_3 Sigmax_6 Sigmax_8 Sigmax_9 +
1.00000 * Sigmax_4 Sigmax_6 Sigmax_7 Sigmax_10 +
1.00000 * Sigmax_5 Sigmax_7 Sigmax_8 Sigmax_11 +
1.00000 * Sigmaz_6 Sigmaz_9 Sigmaz_10 Sigmaz_12 +
1.00000 * Sigmaz_7 Sigmaz_10 Sigmaz_11 Sigmaz_13 +
1.00000 * Sigmaz_8 Sigmaz_9 Sigmaz_11 Sigmaz_14 +
1.00000 * Sigmax_9 Sigmax_12 Sigmax_14 Sigmax_15 +
1.00000 * Sigmax_10 Sigmax_12 Sigmax_13 Sigmax_16 +
1.00000 * Sigmax_11 Sigmax_13 Sigmax_14 Sigmax_17 +
1.00000 * Sigmaz_12 Sigmaz_15 Sigmaz_16 Sigmaz_18 +
1.00000 * Sigmaz_13 Sigmaz_16 Sigmaz_17 Sigmaz_19 +
1.00000 * Sigmaz_14 Sigmaz_15 Sigmaz_17 Sigmaz_20 +
1.00000 * Sigmax_15 Sigmax_18 Sigmax_20 Sigmax_21 +
1.00000 * Sigmax_16 Sigmax_18 Sigmax_19 Sigmax_22 +
1.00000 * Sigmax_17 Sigmax_19 Sigmax_20 Sigmax_23


Lets say I don't want all the last six interaction term in my model which can be done by removing sites(i>=18).
Below I am attaching the example code, where I do not understand how to provide the 2 D array of lattice sites whch I wants to remove.

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    def init_lattice(self, model_params):
site = self.init_sites(model_params)
Lx = model_params.get('Lx', 2)
Ly = model_params.get('Ly', 2)
order = model_params.get('order', 'default')
bc_MPS = model_params.get('bc_MPS', 'infinite')
bc_x = 'periodic' if bc_MPS == 'infinite' else 'open'
bc_x = model_params.get('bc_x', bc_x)
bc_y = model_params.get('bc_y', 'periodic')
assert bc_y in ['open', 'periodic']
bc = [bc_x, bc_y]
lat = IrregularLattice(DualSquare(Lx, Ly, site, order=order, bc=bc, bc_MPS=bc_MPS),remove=[......])
return lat

Attachments
Figure_1.png (72.79 KiB) Viewed 976 times
Johannes
Posts: 198
Joined: 21 Jul 2018, 12:52
Location: UC Berkeley

Re: Irregular lattice site removing doubt

First of all: I've updated the documentation on Monday and added a completely new user-guide page describing many details on lattices, including a small section on irregular hattices on the end.
Moreover, I've added some examples in the doc-string of the tenpy.models.lattice.IrregularLattice itself.

To your question: you specify Lx=3, Ly=3 for the lattice, which produces the figure you attached with 18 sites, so there are no sites 18, 19, 20, ... 22. Those sites appear for example if you have Lx=4, did you mean that?
Which sites do you want to remove? Those on bonds not belonging to any Plaquette of the original square lattice? That would only be 3 (for Ly=3, namely 15, 16, 17 in your figure.
Site 15 corresponds to lattice index (x,y,u) = (3, 0, 1), Site 16 is (x,y,u) = (3, 1, 1) and so on, so I think you want

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IrregularLattice(DualSquare(Lx, Ly, site, order=order, bc=bc, bc_MPS=bc_MPS),
remove=[[Lx-1, y, 1] for y in range(Ly)])


PS: I've moved the topic into the HowTo forum, the "Papers using TeNPy" forum is for the case that you used TeNPy to write an awsome paper you want to tell us about
amankumar
Posts: 17
Joined: 17 Apr 2020, 11:14

Re: Irregular lattice site removing doubt

I am sorry for posting question in "Papers using TeNPy", I don't remember how did I posted it there.
I tried to use Irregular Lattice for Toric Code model by removing those sites which do not belong to any Plaquette of the original square lattice. I am getting an unusual error. Can you help me in this regard?

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File "/tenpy/models/lattice.py", line 544, in lat2mps_idx
i += i_shift * self.N_sites // self.N_rings
TypeError: unsupported operand type(s) for *: 'int' and 'NoneType'

I am attaching the Full Code below.

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# Copyright 2018-2020 TeNPy Developers, GNU GPLv3

import numpy as np

from tenpy.networks.mps import MPS
from tenpy.algorithms import dmrg
from tenpy.models.toric_code import ToricCode

def example_run_TC():
model_params = dict(Lx=3, Ly=3, Jv=1, Jp=1, bc_MPS="infinite", verbose= 1)

Lx = model_params['Lx']
Ly = model_params['Ly']
M = ToricCode(model_params)
product_state=[0]*((2*Ly*Lx)-Ly)
psi = MPS.from_product_state(M.lat.mps_sites(), product_state, bc = "infinite")
dmrg_params = {
'mixer': True,  # setting this to True helps to escape local minima
'trunc_params': {
'chi_max': 100,
'svd_min': 1.e-10,
},
'max_E_err': 1.e-10,
'verbose': 1,
}

results = dmrg.run(psi, M, dmrg_params)
print("Energy per site: ", results['E'])
if __name__ == "__main__":
example_run_TC()



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# Copyright 2018-2020 TeNPy Developers, GNU GPLv3

import numpy as np

from .lattice import Lattice, get_order, _parse_sites,IrregularLattice
from ..networks.site import SpinHalfSite
from .model import MultiCouplingModel, CouplingMPOModel
from ..tools.params import asConfig
from ..tools.misc import any_nonzero

__all__ = ['DualSquare', 'ToricCode']

class DualSquare(Lattice):
def __init__(self, Lx, Ly, sites, **kwargs):
sites = _parse_sites(sites, 2)
basis = np.eye(2)
pos = np.array([[0., 0.5], [0.5, 0.]])
kwargs.setdefault('basis', basis)
kwargs.setdefault('positions', pos)
NN = [(1, 0, np.array([0, 0])), (1, 0, np.array([1, 0])), (0, 1, np.array([-1, 1])),
(0, 1, np.array([0, 1]))]
nNN = [(i, i, dx) for i in [0, 1] for dx in [np.array([1, 0]), np.array([0, 1])]]
nnNN = [(i, i, dx) for i in [0, 1] for dx in [np.array([1, 1]), np.array([-1, 1])]]
kwargs.setdefault('pairs', {})
kwargs['pairs'].setdefault('nearest_neighbors', NN)
kwargs['pairs'].setdefault('next_nearest_neighbors', nNN)
kwargs['pairs'].setdefault('next_next_nearest_neighbors', nnNN)
super().__init__([Lx, Ly], sites, **kwargs)

def ordering(self, order):
if isinstance(order, str):
if order == "default":
priority = (0, 2, 1)
snake_winding = (False, False, False)
return get_order(self.shape, snake_winding, priority)
return super().ordering(order)

class ToricCode(CouplingMPOModel, MultiCouplingModel):
def init_sites(self, model_params):
conserve = model_params.get('conserve', 'parity')
site = SpinHalfSite(conserve)
return site

def init_lattice(self, model_params):
site = self.init_sites(model_params)
Lx = model_params.get('Lx', 2)
Ly = model_params.get('Ly', 2)
order = model_params.get('order', 'default')
bc_MPS = model_params.get('bc_MPS', 'infinite')
bc_x = 'periodic' if bc_MPS == 'infinite' else 'open'
bc_x = model_params.get('bc_x', bc_x)
bc_y = model_params.get('bc_y', 'periodic')
assert bc_y in ['open', 'periodic']
bc = [bc_x, bc_y]
lat=IrregularLattice(DualSquare(Lx, Ly, site, order=order, bc=bc,bc_MPS=bc_MPS),
remove=[[Lx-1, y, 1] for y in range(Ly)])
return lat
def init_terms(self, model_params):
Jv = model_params.get('Jv', 1.)
Jp = model_params.get('Jp', 1.)
# vertex/star term
self.add_multi_coupling(Jv, [('Sigmax', [0, 0], 1), ('Sigmax', [0, 0], 0),
('Sigmax', [-1, 0], 1), ('Sigmax', [0, -1], 0)],category='spins')
# plaquette term
self.add_multi_coupling(Jp, [('Sigmaz', [0, 0], 1), ('Sigmaz', [0, 0], 0),
('Sigmaz', [0, 1], 1), ('Sigmaz', [1, 0], 0)],category='spins')
# done
69,1          Bot


Thanks
Johannes
Posts: 198
Joined: 21 Jul 2018, 12:52
Location: UC Berkeley

Re: Irregular lattice site removing doubt

Sorry, that was a small bug. I've fixed it in 037ad76272825bf6f4de1a72fb4e5529a1fcdec9.
Johannes
Posts: 198
Joined: 21 Jul 2018, 12:52
Location: UC Berkeley

Re: Irregular lattice site removing doubt

By the way, you don't have to modify the model inside the tenpy repo for that, you can do something like this:

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from tenpy.models import toric_code
from tenpy.models.lattice import IrregularLattice

class MyToricCode(toric_code.ToricCode):

def init_lattice(self, model_params):
reg_lat = super().init_lattice(model_params) # calls the ToricCode.init_lattice
Lx, Ly = reg_lat.Ls
lat = IrregularLattice(reg_lat, remove=[[Lx-1, y, 1] for y in range(Ly)])
return lat