Search found 32 matches

by QichengTang
08 Apr 2019, 09:18
Forum: Algorithms
Topic: question about tdvp
Replies: 2
Views: 1655

question about tdvp

Hi, everyone. I'm trying to do tdvp, but there are something in the original paper which I cannot understand. Firstly, why the projector in this form? I know the projector is something like 1 - \sum_N |\psi_N><\psi_N| , but what's the target space here, it seems like we project it onto a basis orort...
by QichengTang
08 Mar 2019, 10:50
Forum: HowTos and FAQ for TeNPy
Topic: Product state results
Replies: 3
Views: 1254

Re: Product state results

I believe it's easy to generate a random product state with a given total charge.
for example, for qubit, it's just a combination of 0 and 1 with a given sum of all elements in the list, you just need to give the number of 0 and 1, and do a random permutation.
by QichengTang
27 Feb 2019, 10:07
Forum: HowTos and FAQ for TeNPy
Topic: Product state results
Replies: 3
Views: 1254

Re: Product state results

I will ask you the question what Johannes asked me: What the "random" state means here? It should be noticed that the charge (quantum number) should be conserved in dmrg, so if your random state has a different total charge, the result will be wrong. Perhaps you can use "RandomUnitaryEvolution" to g...
by QichengTang
22 Feb 2019, 09:34
Forum: HowTos and FAQ for TeNPy
Topic: Scaling of entanglement entropy for iDMRG
Replies: 7
Views: 2235

Re: Scaling of entanglement entropy for iDMRG

hi, everyone. I have to admit i was wrong, and what Umberto said is correct: The original formula is correct, and in infinite dmrg the boundary condition is open. BTW, bart, your scaling method may be wrong. Why you choose the data from a state which is not converged in dmrg? What I remember is: you...
by QichengTang
09 Feb 2019, 13:30
Forum: HowTos and FAQ for TeNPy
Topic: How to generate a random MPS in tenpy
Replies: 5
Views: 1902

Re: How to generate a random MPS in tenpy

Thanks for your reply! In fact, I want to get some states with random entanglement entropy. I know the random unitary time evolution will be a good method. I was thinking about that is there a method can directly obtain these states? The first coming problem is about the charge conserve as you said,...
by QichengTang
31 Jan 2019, 14:16
Forum: HowTos and FAQ for TeNPy
Topic: How to generate a random MPS in tenpy
Replies: 5
Views: 1902

Re: How to generate a random MPS in tenpy

Thanks for your reply. But what i'm looking for is not a random product state. What I want is a general state not a product state. I konw that there is a method to obtain a random state by a random unitary evolution process, but i'm asking a more simple way to get a random state, like by using some ...
by QichengTang
29 Jan 2019, 15:48
Forum: HowTos and FAQ for TeNPy
Topic: Scaling of entanglement entropy for iDMRG
Replies: 7
Views: 2235

Re: Scaling of entanglement entropy for iDMRG

I mean, in iDMRG, the boundary condition is like a periodic boundary condition. So, your problem is you use the wrong formula, you should use a formula for periodic boundary condition when you do an iDMRG calculation. In a finite case, you can choose open boundary condition or periodic, but in tenpy...
by QichengTang
29 Jan 2019, 14:22
Forum: HowTos and FAQ for TeNPy
Topic: Scaling of entanglement entropy for iDMRG
Replies: 7
Views: 2235

Re: Scaling of entanglement entropy for iDMRG

hi, i believe the reason is that in iDMRG the boundary condition is like a periodic boundary condition.
Your formula is for the open boundary condition, and for periodic boundary condition this should be c/3 but not c/6.
I recommend you to read the following two ref: arXiv:hep-th/0405152 and arXiv:0905.4013.
by QichengTang
21 Jan 2019, 13:49
Forum: HowTos and FAQ for TeNPy
Topic: How to generate a random MPS in tenpy
Replies: 5
Views: 1902

How to generate a random MPS in tenpy

how to generate a random MPS? Is the function "npc.Array.from_func" helpful?
PS. I think it's worthy to add a function like "rand_mps".
by QichengTang
17 Jan 2019, 15:18
Forum: HowTos and FAQ for TeNPy
Topic: the truncation in dmrg
Replies: 5
Views: 1809

Re: the truncation in dmrg

Okay, I see. I'm wrong about the truncation protocol in tenpy.
But, it's still kind of weird for me, I mean, the value of 1.e-10 ("svd_min") is a very small number, it should not influence the result, or I'm wrong with some very trivial things?