Search found 407 matches
- 09 Jun 2020, 21:15
- Forum: HowTos and FAQ for TeNPy
- Topic: overlap of ground states at different parameters
- Replies: 7
- Views: 6455
Re: overlap of ground states at different parameters
It's simply psi_1.overlap(psi_2) , or for the normalization as in your formula, psi_1.overlap(psi_2)/psi_1.norm / psi_2.norm . See overlap for more details. For infinite MPS, it's the largest eigenvalue of the transfermatrix, which is not just the overlap <psi_1|psi_2> - the latter is zero for any t...
- 08 Jun 2020, 23:24
- Forum: HowTos and FAQ for TeNPy
- Topic: Adding a site to a chain perpendicularly
- Replies: 6
- Views: 6017
Re: Adding a site to a chain perpendicularly
Sorry if that wasn't clear. It's not included in version 0.6.1 on pip yet, but it's on the github master branch. So you need to install the latest version from github. With pip: pip uninstall physics-tenpy # if you installed it before pip install git+git://github.com/tenpy/tenpy.git or download the ...
- 08 Jun 2020, 16:48
- Forum: HowTos and FAQ for TeNPy
- Topic: Adding a site to a chain perpendicularly
- Replies: 6
- Views: 6017
Re: Adding a site to a chain perpendicularly
Just for your information, this is now possible in the latest version of TeNPy with the help of the tenpy.models.lattice.IrregularLattice, see example in it's docstring and https://tenpy.readthedocs.io/en/latest/ ... tices.html
- 04 Jun 2020, 01:26
- Forum: HowTos and FAQ for TeNPy
- Topic: Finite Chain with different unit cell at the beginning
- Replies: 4
- Views: 5287
- 03 Jun 2020, 02:03
- Forum: HowTos and FAQ for TeNPy
- Topic: tebd on 2d lattice/ MPS with dangling legs
- Replies: 2
- Views: 3979
Re: tebd on 2d lattice/ MPS with dangling legs
Let me understand what you want to do. Do you want to write down a fully-2D PEPS where each tensor has 5 legs, left, right,up, down, physical? And then you somehow extract a single row/column of the PEPS as an MPS, with "dangling" legs (for a row, dangling up and down indices) to apply TEB...
- 03 Jun 2020, 01:24
- Forum: HowTos and FAQ for TeNPy
- Topic: Irregular lattice site removing doubt
- Replies: 4
- Views: 4309
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...
- 26 May 2020, 06:28
- Forum: HowTos and FAQ for TeNPy
- Topic: entanglement_entropy_segment doubt
- Replies: 13
- Views: 13679
Re: entanglement_entropy_segment doubt
1.) The toric code model acutally didn't allow for that, you would have had to override the init_lattice method. I've just updated it in 4cc12c0ab9f38cc970da7e5338a1ee3210964997 to allow torus-boundary conditions with bc_MPS="finite", bc_x="periodic", bc_y="periodic" . ...
- 26 May 2020, 03:43
- Forum: HowTos and FAQ for TeNPy
- Topic: Initializing RenyiDisentangler
- Replies: 2
- Views: 3086
Re: Initializing RenyiDisentangler
Wow, someone interested in the methods of that paper :) Sorry for the bad programming style making it hard to use it without TEBD :? The BackwardsDisentangler needed full access to TEBD, and I wanted to have a uniform interface for the different disentangler classes. Copy/paste works, of course. Alt...
- 26 May 2020, 03:27
- Forum: HowTos and FAQ for TeNPy
- Topic: Non-hermitian Matrices
- Replies: 1
- Views: 3024
Re: Non-hermitian Matrices
TEBD does work for non-hermitian hamiltonians since the commit closing the issue. DMRG does right now not work in this case, since it uses Lanczos which crucially assumes that the hamiltonian is hermitian. You would need to use a different eigensolver for non-hermitian H, and I have now idea how wel...
- 26 May 2020, 02:48
- Forum: HowTos and FAQ for TeNPy
- Topic: Bipartitioning infinite MPS into 2 semi-infinite chains
- Replies: 11
- Views: 9128
Re: Bipartitioning infinite MPS into 2 semi-infinite chains
You want to cut the system into two halves, but get_rho_segment extracts the density matrix for the *few* sites you give as argument, so that's the wrong function. The equations from the cited paper is really what's calculated by average_charge of the MPS (up to the prefactor constants, I believe), ...
- 26 May 2020, 02:23
- Forum: HowTos and FAQ for TeNPy
- Topic: Initial product states
- Replies: 1
- Views: 3099
Re: Initial product states
Having one more up than down electron can only work if you have an odd number of sites. Then you can do, e.g, initial_state = ["up", "down"] * (M.lat.N_sites // 2) initial_state.append("up") If you have an even number of sites and want two more up than down electrons, ...
- 18 May 2020, 05:15
- Forum: HowTos and FAQ for TeNPy
- Topic: Error at example code c_tebd.py
- Replies: 1
- Views: 2662
Re: Error at example code c_tebd.py
Thanks for pointing it out, I've updated it on the master branch.
Unfortunately, it didn't make it into the release of v0.6.0 any more, which I packed last Friday
Unfortunately, it didn't make it into the release of v0.6.0 any more, which I packed last Friday
- 18 May 2020, 05:08
- Forum: HowTos and FAQ for TeNPy
- Topic: entanglement_entropy_segment doubt
- Replies: 13
- Views: 13679
Re: entanglement_entropy_segment doubt
1) It depends on the physical system, not just the lattice! E.g. in the dimer lattice of my previous post, you should define the ordering such that each dimer is nearest-neighbor in the MPS. 3.) The order you plotted here is different from the default one of the tenpy.models.lattice.Honeycomb lattic...
- 15 May 2020, 18:55
- Forum: HowTos and FAQ for TeNPy
- Topic: npc.zeros and labels
- Replies: 2
- Views: 3526
Re: npc.zeros and labels
In the latest version of the master branch, the function definitely has the labels arguments, introduced in 8dd1f93b719074770a9d6cef16f0d89d9fd6229d on Jan. 27th. This change was introduced after the last official release of v0.5.0 on Dez.18 last year, however, so if you used the pip install physics...
- 14 May 2020, 21:17
- Forum: HowTos and FAQ for TeNPy
- Topic: entanglement_entropy_segment doubt
- Replies: 13
- Views: 13679
Re: entanglement_entropy_segment doubt
The square lattice of Leon Balents' paper is a 45-degree rotation compared to the DualSquareLattice we are using. This implies a different geometry for the cylinder axis (going in the [1, 1] direction of our DualSquareLattice), and a different "cut" when you split the MPS between unit cell...
- 14 May 2020, 04:31
- Forum: HowTos and FAQ for TeNPy
- Topic: Apply MPO to MPS
- Replies: 2
- Views: 4166
Re: Apply MPO to MPS
Yes, that's almost right. We're working on something like this in the exp_MPO branch on github. It's not quite ready for use, and we will adjust the interface to better match the other evolution algorithms, but it basically works as a preliminary version, and you can look at it to see how it works. ...
- 13 May 2020, 20:29
- Forum: HowTos and FAQ for TeNPy
- Topic: entanglement_entropy_segment doubt
- Replies: 13
- Views: 13679
Re: entanglement_entropy_segment doubt
1) TeNPy only supports "open" MPS, since peridoic MPS don't have a canonical form. You can make your Model have periodic/toric boundary conditions and still have an open MPS, and TeNPy supports that. The price you pay is that you need the squared bond dimension due to the (expected) entang...
- 13 May 2020, 20:08
- Forum: HowTos and FAQ for TeNPy
- Topic: Square of MPO
- Replies: 3
- Views: 4346
Re: Square of MPO
I'm not sure if the error estimate of arXiv:1711.01104 could be generalized to infinite systems, that would actually be quite usefull.
- 13 May 2020, 06:53
- Forum: HowTos and FAQ for TeNPy
- Topic: Square of MPO
- Replies: 3
- Views: 4346
Re: Square of MPO
I finally took the time to implement at least the "naive" approach of contracting the network with the squared MPO for <psi| H H |psi> in the new variance . Right now it works only for finite systems - for infinite MPS, this is a whole new story, since there is no direct notion of overlaps...
- 07 May 2020, 19:41
- Forum: HowTos and FAQ for TeNPy
- Topic: Translationally Invariant MPS from Single Site DMRG
- Replies: 4
- Views: 5505
Re: Translationally Invariant MPS from Single Site DMRG
Nice workaround! I'd formulate it slightly differnt, though. If we know that there is a translationally invariant, canonical MPS, let's call it C^i_{ab} , then it is related to the MPS tensors found by DMRG via a unitary matrix U : B_0^i = U C^i \quad\text{and}\quad B_1^i = C^i U^{\dagger}. In gener...
- 07 May 2020, 06:26
- Forum: HowTos and FAQ for TeNPy
- Topic: entanglement_entropy_segment doubt
- Replies: 13
- Views: 13679
Re: entanglement_entropy_segment doubt
First of all: the segment [0, 1, 2, 3, 4, 5] is only equivalent to psi.entanglement_entropy()[6] on a finite system. In an infinite system, psi.entanglement_entropy()[6] takes region A to be [..., -4, -3, -2, -1, 0, 1, 2, 3, 4, 5], which is a single cut dividing the system into left and right halfs,...
- 06 May 2020, 02:08
- Forum: HowTos and FAQ for TeNPy
- Topic: Translationally Invariant MPS from Single Site DMRG
- Replies: 4
- Views: 5505
Re: Translationally Invariant MPS from Single Site DMRG
As long as you have more than one tensor in you MPS, they will be different, even with single site DMRG. DMRG optimizes the tensors one after another (in the "sweep"), which immediately breaks the translation invariance in the beginning. If you model is translation invariant and the ground...
- 05 May 2020, 23:26
- Forum: HowTos and FAQ for TeNPy
- Topic: code issue TFI2D model implementation
- Replies: 1
- Views: 5033
Re: code issue TFI2D model implementation
Please include at least the error message for requests like this. It seems to be just a python issue, line 31 of the code above, lattice is not defined. When adding the line from tenpy.models import lattice in the beginning, it runs fine. I presume you want to extend the TFI model and add further te...
- 05 May 2020, 22:51
- Forum: HowTos and FAQ for TeNPy
- Topic: Preparing state with specified particle filling
- Replies: 4
- Views: 7626
Re: Preparing state with specified particle filling
We allow a fractional filling n/L where n \in \mathbb{Z} is the number of particles, and L the number of sites in the MPS (or for infinite MPS: in the MPS unit cell). So a filling of 3/10 particles is "commensurate" in that sense. Incommensurate would be and average filling of an irration ...
- 05 May 2020, 22:27
- Forum: HowTos and FAQ for TeNPy
- Topic: entanglement_entropy_segment doubt
- Replies: 13
- Views: 13679
Re: entanglement_entropy_segment doubt
Read the documentation at entanglement_entropy_segment . There is another parameter first_site , where this segment starts. If you use segment=[0, 1, 2] and don't specify first_site , it will default to the segments on sites [0, 1, 2] [1, 2, 3] [2, 3, 4] ... Each of them gives you one number, result...