Search found 15 matches

by Umberto Borla
23 Sep 2019, 15:03
Forum: HowTos and FAQ for TeNPy
Topic: how to write a three-site interaction?
Replies: 4
Views: 1686

Re: how to write a three-site interaction?

@QuichengTang: I'm glad to hear that this was useful.

@Johannes: Thanks for pointing it out, I forgot about it. I fixed it ;)
by Umberto Borla
10 Sep 2019, 17:17
Forum: HowTos and FAQ for TeNPy
Topic: how to write a three-site interaction?
Replies: 4
Views: 1686

Re: how to write a three-site interaction?

Hi! Using the multi-coupling model, you can use the function add_multi_coupling in the following way: self.add_multi_coupling(lambda_, 0, "Sigmax", [(0, "Sigmaz", 1), (0, "Sigmaz", 2)]) self.add_multi_coupling(lambda_, 0, "Sigmaz", [(0, "Sigmaz", 1), (0, "Sigmax", 2)]) to add the three-body terms in...
by Umberto Borla
05 Jul 2019, 16:14
Forum: HowTos and FAQ for TeNPy
Topic: Finite Chain with different unit cell at the beginning
Replies: 4
Views: 1399

Re: Finite Chain with different unit cell at the beginning

Thanks a lot for the quick reply! I imagined that changing the lattice would be enough, but I was not sure how to do. I'll see if I can manage to carry out the steps that you suggested. :)
by Umberto Borla
04 Jul 2019, 14:56
Forum: HowTos and FAQ for TeNPy
Topic: Finite Chain with different unit cell at the beginning
Replies: 4
Views: 1399

Finite Chain with different unit cell at the beginning

I am struggling with the following issue: I have a 1D lattice (chain) that consists of a repeated unit cell formed by two different sites (a spin-half site and a fermionic site). If I realize an open chain by repeating the unit cell L times, the first site will always be a spin site and the last one...
by Umberto Borla
13 Mar 2019, 10:52
Forum: HowTos and FAQ for TeNPy
Topic: Finite DMRG not working after update to new version
Replies: 4
Views: 1119

Re: Finite DMRG not working after update to new version

Thanks for the quick fix, it is working as expected now. :)
by Umberto Borla
12 Mar 2019, 17:34
Forum: HowTos and FAQ for TeNPy
Topic: Finite DMRG not working after update to new version
Replies: 4
Views: 1119

Re: Finite DMRG not working after update to new version

Hi! Thanks for the quick reply!
No, I find such error consistently every time I use finite DMRG. Even the example file xxz_groundstate, after a clean reinstall, does not run. Does it run without errors in the version that you have?
by Umberto Borla
12 Mar 2019, 17:02
Forum: HowTos and FAQ for TeNPy
Topic: Finite DMRG not working after update to new version
Replies: 4
Views: 1119

Finite DMRG not working after update to new version

Hi! After some months I finally decided to update to the newest version of TeNpy, and I found that my code does not work whenever it involves finite DMRG. The error that I get is: KeyError: "Label not found: '(vR.p1)', current labels: ['(vL.p0)', '(p1.vR)']" So it seems that something goes wrong wit...
by Umberto Borla
12 Feb 2019, 11:09
Forum: HowTos and FAQ for TeNPy
Topic: Scaling of entanglement entropy for iDMRG
Replies: 7
Views: 1853

Re: Scaling of entanglement entropy for iDMRG

Hi! I am also looking into the scaling of S with \log \xi to extract the central charge and from what I read the relation you originally posted S \approx \frac{c}{6}\log \xi should be the correct one even for iDMRG. Apart from Calabrese and Cardy's original paper, here is a reference where they do i...
by Umberto Borla
15 Nov 2018, 10:03
Forum: Implementations
Topic: Multi-Site Expectation Value
Replies: 6
Views: 2758

Re: Multi-Site Expectation Value

Hi! This is the function modified according to your useful suggestions: def _term_to_jw(self, term, op_string = "JW"): """Given a term that is a tensor product of several operators acting on possibly non-neighboring sites [i_min, ... i_n, ... , i_max], this puts Jordan-Wigner strings where appropria...
by Umberto Borla
13 Nov 2018, 10:18
Forum: Implementations
Topic: Multi-Site Expectation Value
Replies: 6
Views: 2758

Re: Multi-Site Expectation Value

I implemented this function that takes a term containing operators acting on non-neighbouring sites and returns a list of operators, obtained by filling the intermediate sites with "Id" or "JW" where appropriate. The output can be used by the method expectation_value_multi_sites def _term_to_jw(self...