# \#gate\_evolution **URL:** https://itensor.discourse.group/tag/gate-evolution/8.md [Latest](https://itensor.discourse.group/latest.md) · [Categories](https://itensor.discourse.group/categories.md) · [Tags](https://itensor.discourse.group/tags.md) --- ## [Error while calculating out-of-time correlators](https://itensor.discourse.group/t/error-while-calculating-out-of-time-correlators/2603)
**Author:** [@asing](https://itensor.discourse.group/u/asing)\ **Replies:** 5\ **Last updated:** [April 10, 2026, 11:34am UTC](https://itensor.discourse.group/t/error-while-calculating-out-of-time-correlators/2603 "2026-04-10T11:34:50Z")
Hi! In the process of calculating OTOC’s for a spin chain mode, I came across a strange error when I perform backward time evolution. In the following code, I am performing C\_{i1}(i,t) = \\langle \\psi\_{init} | S^z\_i(… --- ## [State preparation using variational quantum circuit ansatz](https://itensor.discourse.group/t/state-preparation-using-variational-quantum-circuit-ansatz/2081)
**Author:** [@talentkeychen](https://itensor.discourse.group/u/talentkeychen)\ **Replies:** 3\ **Last updated:** [October 29, 2024, 1:24pm UTC](https://itensor.discourse.group/t/state-preparation-using-variational-quantum-circuit-ansatz/2081 "2024-10-29T13:24:09Z")
Hi everyone, Not sure if this question truly belongs to the ITensor genre, but anyway I already struggled for quite some time before I decided to post here for help. So basically my goal is to perform state preparation… --- ## [Error related to errorMPOProd, and time-evolution (TEBD)](https://itensor.discourse.group/t/error-related-to-errormpoprod-and-time-evolution-tebd/1721)
**Author:** [@subhajyoti.pal](https://itensor.discourse.group/u/subhajyoti.pal)\ **Replies:** 1\ **Last updated:** [May 17, 2024, 8:07am UTC](https://itensor.discourse.group/t/error-related-to-errormpoprod-and-time-evolution-tebd/1721 "2024-05-17T08:07:50Z")
Hello Everyone, We are facing two issues. We were checking the result of the function errorMPOProd for a two-site operator (A) on a ground state (|G\\rangle) obtained using DMRG, where the Hamiltonian (H) does not con… --- ## [Applying 4-site gates to PEPS with ITensorNetworks](https://itensor.discourse.group/t/applying-4-site-gates-to-peps-with-itensornetworks/1618)
**Author:** [@rafa-carreira](https://itensor.discourse.group/u/rafa-carreira)\ **Replies:** 2\ **Last updated:** [April 5, 2024, 12:35pm UTC](https://itensor.discourse.group/t/applying-4-site-gates-to-peps-with-itensornetworks/1618 "2024-04-05T12:35:19Z")
I’m trying to implement a code performing TEBD for a toric code Hamiltonian in a 2D square lattice using ITensorNetworks. I’m facing an issue related to applying a 4-site gate to a PEPS and retrieving the state as a PEPS… --- ## [MPS time evolution, apply function (julia) much slower than gateTEvol (c++)](https://itensor.discourse.group/t/mps-time-evolution-apply-function-julia-much-slower-than-gatetevol-c/1131)
**Author:** [@iChaker](https://itensor.discourse.group/u/iChaker)\ **Replies:** 8\ **Last updated:** [October 6, 2023, 2:46pm UTC](https://itensor.discourse.group/t/mps-time-evolution-apply-function-julia-much-slower-than-gatetevol-c/1131 "2023-10-06T14:46:33Z")
I am trying to run time evolution on an MPS, but I noticed that Julia is much slower than c++. To confirm this I used the example codes provided in the documentation that implement TEBD on a one-dimensional Heisenberg mo… --- ## [Ground state of a disordered model from TEBD](https://itensor.discourse.group/t/ground-state-of-a-disordered-model-from-tebd/1049)
**Author:** [@mozhik](https://itensor.discourse.group/u/mozhik)\ **Replies:** 10\ **Last updated:** [July 23, 2023, 6:04pm UTC](https://itensor.discourse.group/t/ground-state-of-a-disordered-model-from-tebd/1049 "2023-07-23T18:04:46Z")
Hi Miles/Others! I have the following question: Suppose I want to find a GS of the XXZ chain in a random magnetic field in the z direction. I want to use the imaginary-time TEBD algorithm, as implemented in ITensor via … --- ## [Difference between applying ITensor gates to MPO](https://itensor.discourse.group/t/difference-between-applying-itensor-gates-to-mpo/816)
**Author:** [@tsegev](https://itensor.discourse.group/u/tsegev)\ **Replies:** 4\ **Last updated:** [May 23, 2023, 7:57am UTC](https://itensor.discourse.group/t/difference-between-applying-itensor-gates-to-mpo/816 "2023-05-23T07:57:01Z")
Hey all, I have some question about why there is a difference using the apply function and developing a MPS on time with ITensor gates between making a MPO and using the “TDVP”. I will to write a simple example to illu… --- ## [Adding ITensors objects with different index sites](https://itensor.discourse.group/t/adding-itensors-objects-with-different-index-sites/452)
**Author:** [@tsegev](https://itensor.discourse.group/u/tsegev)\ **Replies:** 12\ **Last updated:** [October 15, 2022, 3:34am UTC](https://itensor.discourse.group/t/adding-itensors-objects-with-different-index-sites/452 "2022-10-15T03:34:04Z")
HI all, I have a question about how to add two Hamiltonians which runs over different site elements. My system is a spin chain that run from 1 to n. Their is an inner interaction between the site 1:n-1, and a coupling … --- ## [generate Haar random gates](https://itensor.discourse.group/t/generate-haar-random-gates/58)
**Author:** [@jisutich](https://itensor.discourse.group/u/jisutich)\ **Replies:** 5\ **Last updated:** [April 20, 2022, 8:42pm UTC](https://itensor.discourse.group/t/generate-haar-random-gates/58 "2022-04-20T20:42:30Z")
Hi, I try to use itensor to simulate the measurement phase transition. Basically I want both Haar random unitary matrices and random measurements during the time evolution. So I wrote a short code using LinearAlgebra …