TeNPy Forum

I am computing two quantities which I expect should give me the same answer but they are not in the fermi Hubbard model. cc_ij = psi.correlation_function("Cdu", "Cu")+psi.correlation_function("Cdd", "Cd") print(cc_ij[1][2]) print(psi.expectation_value_term([('...

Hi I am interested in doing the finite temperature study for Fermi Hubbard model, but it seems the developed subroutine only works for spin system. Is it straightforward to write the infinite temperature state using the already present subroutines, if I change the local Hilbert space to four dimensi...

Yes, I want to project at single site only. What will be the "state" argument in this function "project_local(psi, i, state)", if I want to project to up state at site I ?

Dear Johanees,

Is there a simple way to project a state \psi to some up or down state at choosen site i ?

Dear Developers, I have query related to Disentangler implementation in TeNPy. I can see, one can use the existing disentangler under the subroutine PurificationTEBD, when beta(1/Temp.) evolving the state, looks typically made for one-d model. But If one wants to beta evolve the state using Purifica...

Dear Johannes I was interested in to provide the different types of boundary condition in y direction for a cylinder. I want a spiral winding of chain kind of boundary condition over cylinder(may be I am after bc_shift routine but I don't know how to use it). I think usual boundary condition is just...

Thanks for the update, I got it. Does add_onsite also support this array data type for strength? May be, Now I am asking an offset question of this thread, actually I was interested in to provide the different types of boundary condition in y direction for a cylinder. I want a spiral winding of chai...

Thanks a lot! I have another basic question related to model interaction strength. Is there a way to put different interaction strength at each vertex in topic code model, like can I provide a array of strength parameter instead of just Jv. self.add_multi_coupling(-Jv, [('Sigmax', [0, 0], 1), ('Sigm...

I still did not get the code, can you explain bit more. psi0 = MPS.from_product_state(...) states = dmrg_params['orthogonal_to'] = [] So, here we create an initial MPS and then in next line I am confused, does it just add another parameter or routine orthogonal_to in dict dmrg_params. for i in range...

Thanks Johannes 1.) I guess the code line psi = psi0.copy() should be before the for loop, otherwise it will keep using the initial matrix product state(that is psi0 copy). 2.) Also it give me an error saying: File "/home/aman/tenpy-master2/tenpy-master/examples/tenpy/algorithms/mps_sweeps.py&q...

Hi I am interested in to know the excited states of Kiteav's Toric code model. I was going through the documentation to understand how to use it. Can you briefly explain more how to use tenpy for evaluating excited states for lets say first two excited states only. Here is my short code, where I am ...

Thank you for the response. I have another difficulty in this part, I saw source code of get_rho_segment , where sorting is done for segment sites. So If I am evaluating \rho_{ij} , where index i>j , and I will transform it into a 4\times 4 matrix. So, now I am interested in \rho_{ji} density matrix...

Can I see my two site reduced density matrix in this below format, where I can get to know about each elements of the matrix. \begin{matrix} c_{\uparrow_i\uparrow_j\uparrow_i\uparrow_j} & c_{\uparrow_i\uparrow_j\uparrow_i\downarrow_j} & c_{\uparrow_i\uparrow_j\downarrow_i\uparrow_j} &c_{...

1.) Is there a way to get full \rho_i in matrix form or do I have to calculate each matrix element separately as you suggested above. 2.) Also can I calculate this quantity \langle \Psi | \downarrow_i\rangle , as one way I think of by taking square root of corresponding density matrix element, but t...

Hi I want to know, is there a way to calculate probability to find particle at any site i in up (or down) state? Like if I have a state |\Psi> in MPS form and I want to evaluate this quantity <\Psi|down_i> , where |down_i> is linear combination of all simple basis state where at site i it is down an...

Yes while copying code here, I missed that term, which I have updated now. But still I did not understood this distinct behaviour of ground state with or without parity.
Also, how to implement total Sz conserve symmetry here?

Yes I am considering Ferromagnetic Heisenberg model on hexagonal lattice. Here is my code from tenpy.algorithms import dmrg import numpy as np from mps import MPS from tenpy.models.lattice import Lattice, get_order, _parse_sites,Honeycomb from tenpy.networks.site import SpinHalfSite from tenpy.model...

Thanks That is fine, when parity is conserved, state is in all up state plus down state, which is confirmed by zero expectation vale of Sz on a site. And in other case, when I turn off parity, I get state to be in all up configuration, confirmed by "one" expectation value of Sz on a site. ...

Hi
If you need more details, or did not understood my question, please let me know.
Thanks

Thanks it works fine, but only for small bond dimension. I have another conceptual question in dmrg, I was simulating ferromagnetic heisenberg model using tenpy, and evaluated ground state entanglement entropy for some subsystem. I got Log(2) as answer, as this is obvious ground state preserves spin...

Hi I wanted to evaluate entanglement entropy for a segment of sites with function entanglement_entropy_segment(). But this can not take more than or equal 12 sites as memory issue. Can I exploit lattice symmetries like translation one using tenpy package, and can extend my segment size to more than ...

Thank you for the update to allow torus-boundary conditions. And as you pointed I implemented it on Toric Code model and bond dimension is squared as compared to infinite cylinder. 1.) But now I am getting back to my old thread question. I am trying to evaluate entanglement for a system size L_x=L_y...

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 hel...

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 s...

I understand that, I deliberately tried to change the lattice basis vector and order in Honeycomb lattice. 1.) How to change the model such that it supports toroidal boundary condition, as you suggested in earlier post. Can you guide me for this your famous toric code example. 2.) I tried to impleme...