Search found 429 matches
- 01 Apr 2022, 01:39
- Forum: HowTos and FAQ for TeNPy
- Topic: MPS winding for 'new' lattice
- Replies: 2
- Views: 2725
Re: MPS winding for 'new' lattice
I think you're on the right track. I presume your PhtantasticLattice is derived from the base lattice class. What you should do is override the ordering method, similar as is done in the the tenpy.models.lattice.Honeycomb lattice - take a look at the source there. You want the structure def ordering...
- 22 Mar 2022, 01:55
- Forum: HowTos and FAQ for TeNPy
- Topic: How Does Block Absorption Work in MPS DMRG
- Replies: 1
- Views: 2458
Re: How Does Block Absorption Work in MPS DMRG
Yes, the main idea is that you *never* have the Schmidt states as whole, but only as (partial) MPS, recursivley adding tensors to get the Schmidt states on the next bond; see also Figure 4 c) of our paper 1805.00055 . Indeed, the formula you wrote gives the Schmidt states |a_l> in the basis of |a_{l...
- 22 Mar 2022, 01:22
- Forum: HowTos and FAQ for TeNPy
- Topic: iDMRG sweep schedule
- Replies: 3
- Views: 4275
Re: iDMRG sweep schedule
You're referring to the update_LP_RP defined in get_sweep_schedule for n=2 , i.e. a two-site update. As you can see from the i0s, move_right variables, we do 2L updates in total, each updating 2 sites, in the order (0, 1), ..., (L-2, L-1), (L-1, L), (L, L+1), (L-1, L), ..., (1, 2) . Note that this i...
- 22 Mar 2022, 00:52
- Forum: HowTos and FAQ for TeNPy
- Topic: Disentangler
- Replies: 1
- Views: 2727
Re: Disentangler
The disentangling of purified states indeed currently only works for 1D chains where you can do TEBD. In practice, we found in 1711.01288 that only the "backwards" disentangler leads to a speed-up - while we were able to reduce the entanglement further with the other disentanglers, they di...
- 22 Mar 2022, 00:06
- Forum: HowTos and FAQ for TeNPy
- Topic: parallel computing
- Replies: 4
- Views: 4669
Re: parallel computing
Hi Ling, sorry for the late reply!
Indeed, with your question I realized that we probably don't document this sufficiently.
I've just added a corresponding section in the simulation introduction.
Does that answer your questions?
Indeed, with your question I realized that we probably don't document this sufficiently.
I've just added a corresponding section in the simulation introduction.
Does that answer your questions?
- 21 Mar 2022, 22:26
- Forum: HowTos and FAQ for TeNPy
- Topic: How Do I Define New Operators in TenPy
- Replies: 4
- Views: 3900
Re: How Do I Define New Operators in TenPy
Thanks for the reply Jirawat! Your answer nicely explains how to add an onsite operator (given as a matrix) to a local site. Expanding on this, let me just mention that for a CouplingMPOModel it should often be enough to overwrite the init_sites method. A non-trivial example adding an operator P0 pr...
- 09 Feb 2022, 08:39
- Forum: Algorithms
- Topic: Problems with add_local_term and H.c
- Replies: 1
- Views: 12476
Re: Problems with add_local_term and H.c
This case wasn't tested properly, so a bug could sneak in... I've just fixed it in 72f79cce1f7dd04607027322763db2a6b80466e3 and added proper tests. The index error indicates that you didn't actually set the option explicit_plus_hc=True , otherwise it would not have occured... You need to do that as ...
- 09 Feb 2022, 07:19
- Forum: Algorithms
- Topic: Question about the Hamiltonian MPO
- Replies: 1
- Views: 9195
Re: Question about the Hamiltonian MPO
MPOs are extensive sums of local terms; thus they take a Jordan block form W = \begin{pmatrix} 1 & C & D \\ 0 & A & B \\ 0 & 0 & 1 \end{pmatrix} = \text{e.g. for transverse field ising} \begin{pmatrix} 1 & X & - Z \\ 0 & 0 & X \\ 0 & 0 & 1 \end{pmatrix...
- 09 Feb 2022, 06:48
- Forum: HowTos and FAQ for TeNPy
- Topic: How to convert iMPS to finite MPS?
- Replies: 2
- Views: 13263
Re: How to convert iMPS to finite MPS?
Why? What do you want to do with the state afterwards? Yes, of course, you can just insert a projector onto the index with maximal singualar value at the boundary, i.e. bond dimension 1, and formally declare it a finite MPS. But this truncation is likely not the "optimal" state of maximal ...
- 27 Jan 2022, 19:58
- Forum: HowTos and FAQ for TeNPy
- Topic: Problems with segment boundaries for TDVP
- Replies: 1
- Views: 2695
Re: Problems with segment boundaries for TDVP
I'm sorry that this wasn't clear, but TeNPy's TDVP isn't intended to be used with segment boundary conditions; as of now, TeNPy only supports segment MPS for DMRG. There, the idea is to just keep the state outside of the segment (or "window" in the literature) fixed during the optimization...
- 11 Jan 2022, 10:45
- Forum: HowTos and FAQ for TeNPy
- Topic: How to use random MPS to acess all ground states
- Replies: 2
- Views: 2899
Re: How to use random MPS to acess all ground states
Since you apply 6 steps of randomizing, it might still have some "memory" of the initial state. This function takes an initlal MPS, I guess you take an initial product state. Did you try using another one? It's not completely clear to me what initial states the authors of 1208.2623 took, j...
- 11 Jan 2022, 10:26
- Forum: HowTos and FAQ for TeNPy
- Topic: Periodic versus Open Boundary Conditions
- Replies: 5
- Views: 5761
Re: Periodic versus Open Boundary Conditions
For two dimensional systems, there can be separate boundary conditions in x and y, hence the bc_x and bc_y, which really are just the two values for the
So yes, for a 1D lattice, just putting
bc=[bc_x, bc_y]
of the lattice.So yes, for a 1D lattice, just putting
bc='periodic'
is the correct thing to get periodic boundary conditions.- 11 Jan 2022, 09:56
- Forum: HowTos and FAQ for TeNPy
- Topic: Two component Bose-Hubbard model
- Replies: 4
- Views: 5993
Re: Two component Bose-Hubbard model
See the reply in the separate thread
- 11 Jan 2022, 09:55
- Forum: HowTos and FAQ for TeNPy
- Topic: DMRG of Two Component Bose-Hubbard Model
- Replies: 1
- Views: 3686
Re: DMRG of Two Component Bose-Hubbard Model
Welcome to TenPy, happy new year, and sorry for the long delay in the answer, I had a few things I needed to finish before Christmas..... I think the issue here is that the mixer is disabled, just try setting 'mixer': True . The reason why you need the mixer is that you always just optimize two site...
- 10 Jan 2022, 13:52
- Forum: HowTos and FAQ for TeNPy
- Topic: If/How to avoid: "final DMRG state not in canonical form..."
- Replies: 4
- Views: 5542
Re: If/How to avoid: "final DMRG state not in canonical form..."
Hi Pablo, I hope you also had some nice holidays and wish you a happy new year! The log files should report the "norm_error" - is it close to zero in your case? You can also explicitly check the output of norm_test to check whether the state is in in canonical form. (To be clear, psi.test_...
- 10 Jan 2022, 13:38
- Forum: HowTos and FAQ for TeNPy
- Topic: Questions Regarding Implementation of a 1D Lattice of Bosons
- Replies: 1
- Views: 2186
Re: Questions Regarding Implementation of a 1D Lattice of Bosons
Question 1: It's a dense matrix representation of the N (=particle number) operator. If you truncate to nmax=10, you have 11 local basis states |n>, where n=0,...,10 is the boson number. Hence, N is 11x11 matrix, with n on the diagonal. Question 2/3/4: The cutoff nmax for the Site is the maximal bos...
- 09 Dec 2021, 20:30
- Forum: HowTos and FAQ for TeNPy
- Topic: Periodic versus Open Boundary Conditions
- Replies: 5
- Views: 5761
- 06 Dec 2021, 20:11
- Forum: HowTos and FAQ for TeNPy
- Topic: M.H_MPO and SWAP gate in SpinChain model
- Replies: 2
- Views: 2460
Re: M.H_MPO and SWAP gate in SpinChain model
To be honest, I'm quite surprised by 2102.10188 that it actually seems to work with MPS. They simulate eq. 2, with all-to-all couplings H=\sum_{i<j} S_i \cdot S_j . Naively, I would have expected much more entanglement than only ~log(N) to build up with the time evolution. On the other hand, it kind...
- 06 Dec 2021, 19:03
- Forum: HowTos and FAQ for TeNPy
- Topic: How to Successfully Install TenPy on Windows
- Replies: 3
- Views: 3008
Re: How to Successfully Install TenPy on Windows
Welcome! It looks like conda is only looking in the win-32 channel, i.e. for a 32-bit package. However, we've only packaged/compiled a 64-bit version, since virtually all hardware (on which you'd like to run TeNPy) these days has 64-bit CPUs. Is your Windows 64 bit? Then you should also download the...
- 08 Nov 2021, 19:30
- Forum: HowTos and FAQ for TeNPy
- Topic: Periodic versus Open Boundary Conditions
- Replies: 5
- Views: 5761
Re: Periodic versus Open Boundary Conditions
I'm not too surprised that W_II fails for this. Intuitively, the W_I/W_II methods from the ExpMPOEvolution approximates e^{-iH dt} by taking into account non-overlapping terms of H; it is not designed for a long-range coupling going accross the whole system (which you get by using periodic BC for a ...
- 12 Oct 2021, 17:24
- Forum: HowTos and FAQ for TeNPy
- Topic: How to efficiently save and resume calculation
- Replies: 3
- Views: 4261
Re: How to efficiently save and resume calculation
Indeed, the tenpy.simulations.Simulation classes are built to support exactly this in a generic way for the various algorithms. The idea is that you start your simulation with `run_simulation`, it saves snapshot at certain checkpoints (e.g. during DMRG between sweeps), and you can resume from these ...
- 12 Oct 2021, 17:14
- Forum: HowTos and FAQ for TeNPy
- Topic: spin inversion & reflection symmetry
- Replies: 1
- Views: 3840
Re: spin inversion & reflection symmetry
1) You refer to H = ZZ - g_x X, where the spin flip symmetry is a product(X). TeNPy implements the TF Ising model as H = XX - g Z, such that the symmetry becomes product(Z), i.e. the parity of sum(Z) is conserved. This is implemented in tenpy.models.tf_ising.TFIChain , it will by default use conserv...
- 12 Oct 2021, 16:27
- Forum: HowTos and FAQ for TeNPy
- Topic: overhead of creating tvdp engines
- Replies: 1
- Views: 2054
Re: overhead of creating tvdp engines
Just initializing the two TDVP environments independently at the same time will not yield the correct result, since each engine has an MPOEnvironment for the partial contractions of <psi|H|psi>, and the one of engine1 will not get updated during the evolution of engine2. You could call engine1.envir...
- 12 Oct 2021, 16:11
- Forum: HowTos and FAQ for TeNPy
- Topic: TDVP for MPO which is not nearest-neighbor w.r.t. MPO index
- Replies: 1
- Views: 2121
Re: TDVP for MPO which is not nearest-neighbor w.r.t. MPO index
You chose an artificial test case of completely decoupled spins; the spin pairs 2-4 and 3-5 will just each propagate together. This is basically a product state, except that 2-4 and 3-5 are entangled. After a single time step with the ExpMPOEvolution, the MPS bond dimension grew to include the Schmi...
- 12 Oct 2021, 15:48
- Forum: HowTos and FAQ for TeNPy
- Topic: single honeycomb cell from the honeycomb lattice class
- Replies: 1
- Views: 2012
Re: single honeycomb cell from the honeycomb lattice class
Take a look at the irregular lattices; exactly this example can be found in the user guide.
Since the commit b49f0e0 that I just pushed, you can do that by adding the model parameter "irregular_remove".
Since the commit b49f0e0 that I just pushed, you can do that by adding the model parameter "irregular_remove".