# TDVP with Sum of MPOs in C++ ITensor, Like DMRG

**URL:** <https://itensor.discourse.group/t/tdvp-with-sum-of-mpos-in-c-itensor-like-dmrg/2235>\
**Category:** ITensor C++ Questions\
**Created:** [February 5, 2025, 4:31pm UTC](https://itensor.discourse.group/t/tdvp-with-sum-of-mpos-in-c-itensor-like-dmrg/2235 "2025-02-05T16:31:53Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Sambu\_1234](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@Sambu\_1234](https://itensor.discourse.group/u/Sambu_1234)\
**Post date:** [February 5, 2025, 4:31pm UTC](https://itensor.discourse.group/t/tdvp-with-sum-of-mpos-in-c-itensor-like-dmrg/2235/1 "2025-02-05T16:31:53Z")

</div>

Hi,  
I am working with ITensor in C++ and looking to perform TDVP time evolution for a Hamiltonian expressed as a sum of multiple MPOs.

In DMRG, Hamiltonians can be handled as a sum of multiple MPOs (e.g., H=H\_1+H\_2+H\_3) without explicitly summing them, improving both efficiency and accuracy. Instead, the algorithm internally loops over the MPO terms.

Is there a similar approach for TDVP within the C++ ITensor framework that allows time evolution to be performed efficiently using separate MPOs without explicitly forming a single summed MPO?

Thanks in advance!

Best  
Sambu

---

<div class="post-metadata">

**Author:** ![mtfishman](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/mtfishman/32/11_2.png) [@mtfishman](https://itensor.discourse.group/u/mtfishman)\
**Post date:** [February 6, 2025, 1:25pm UTC](https://itensor.discourse.group/t/tdvp-with-sum-of-mpos-in-c-itensor-like-dmrg/2235/2 "2025-02-06T13:25:34Z")

</div>

Have you tried it? I see it defined here: [TDVP/tdvp.h at af8d784b9ed77df69a43b57b2b6ccee2a79bce35 · ITensor/TDVP · GitHub](https://github.com/ITensor/TDVP/blob/af8d784b9ed77df69a43b57b2b6ccee2a79bce35/tdvp.h#L109-L118)

---

<div class="post-metadata">

**Author:** ![Sambu\_1234](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@Sambu\_1234](https://itensor.discourse.group/u/Sambu_1234)\
**Post date:** [February 13, 2025, 10:59am UTC](https://itensor.discourse.group/t/tdvp-with-sum-of-mpos-in-c-itensor-like-dmrg/2235/3 "2025-02-13T10:59:25Z")

</div>

Hi,  
Sorry for the delayed response. Yes, I’ve tried it, and it works well for different MPOs.

Thanks!