# General Discussion **URL:** https://itensor.discourse.group/c/general/9.md [Latest](https://itensor.discourse.group/latest.md) · [Categories](https://itensor.discourse.group/categories.md) · [Tags](https://itensor.discourse.group/tags.md) --- ## [Please Read: Make It Easier to Help You](https://itensor.discourse.group/t/please-read-make-it-easier-to-help-you/7)
**Author:** [@system](https://itensor.discourse.group/u/system)\ **Replies:** 0\ **Last updated:** [March 30, 2022, 10:43am UTC](https://itensor.discourse.group/t/please-read-make-it-easier-to-help-you/7 "2022-03-30T10:43:56Z")
This community is for technical support and discussion of the ITensor Software, and official packages based on ITensor. We highly recommend using the Julia version of ITensor. It has the same or better performance compa… --- ## [About the General Discussion category](https://itensor.discourse.group/t/about-the-general-discussion-category/21)
**Author:** [@miles](https://itensor.discourse.group/u/miles)\ **Replies:** 0
This category is for general discussion that doesn’t fit into the other categories. Please read the our guide to using the forum before posting, to make it easier for us to help you! --- ## [Where should I start learning iTensor as a beginner?](https://itensor.discourse.group/t/where-should-i-start-learning-itensor-as-a-beginner/2637)
**Author:** [@MHSZ](https://itensor.discourse.group/u/MHSZ)\ **Replies:** 1\ **Last updated:** [September 11, 2026, 12:34am UTC](https://itensor.discourse.group/t/where-should-i-start-learning-itensor-as-a-beginner/2637 "2026-09-11T00:34:59Z")
Hi everyone, I’m a master’s student studying Quantum Computing and Quantum Information. My semester starts in about 10 days, and I’d like to get a head start on learning iTensor. I spoke with my advisor, and they recom… --- ## [time dependent correlators with electrons](https://itensor.discourse.group/t/time-dependent-correlators-with-electrons/2630)
**Author:** [@Leon](https://itensor.discourse.group/u/Leon)\ **Replies:** 1\ **Last updated:** [July 24, 2026, 3:26pm UTC](https://itensor.discourse.group/t/time-dependent-correlators-with-electrons/2630 "2026-07-24T15:26:06Z")
Hello there, I did post a related question to this one trying to solve a subsidiary problem. Here I would like to present on what I am failing to implement i.e. to use ITensor properly. I suspect this to be a rather gen… --- ## [iDMRG package built on ITensors.jl](https://itensor.discourse.group/t/idmrg-package-built-on-itensors-jl/2615)
**Author:** [@zhlphy](https://itensor.discourse.group/u/zhlphy)\ **Replies:** 3\ **Last updated:** [July 3, 2026, 11:12am UTC](https://itensor.discourse.group/t/idmrg-package-built-on-itensors-jl/2615 "2026-07-03T11:12:58Z")
Dear all, I notice a lot of people here are looking for iDMRG in ITensor (so do I). Recently, I have developed one built on ITensors.jl and ITensorMPS.jl: iDMRG It implements: iDMRG using MPS swapping VUMPS (hopeful… --- ## [MPS and MPO in Quantum Circult](https://itensor.discourse.group/t/mps-and-mpo-in-quantum-circult/2577)
**Author:** [@yedi](https://itensor.discourse.group/u/yedi)\ **Replies:** 1\ **Last updated:** [January 30, 2026, 8:43pm UTC](https://itensor.discourse.group/t/mps-and-mpo-in-quantum-circult/2577 "2026-01-30T20:43:19Z")
Dear porfessors, In my previous work, I have used DMRG in ITensor to study the properties of two-dimensional Fermi–Hubbard model. I am also aware that ITensor provides a module for quantum circuit simulation. This natu… --- ## [Non-Hermitian DMRG in ITensor](https://itensor.discourse.group/t/non-hermitian-dmrg-in-itensor/2536)
**Author:** [@tipfom](https://itensor.discourse.group/u/tipfom)\ **Replies:** 4\ **Last updated:** [December 19, 2025, 7:11am UTC](https://itensor.discourse.group/t/non-hermitian-dmrg-in-itensor/2536 "2025-12-19T07:11:42Z")
Hello everyone, I implemented a non-Hermitian DMRG variant \[1, 2\] in ITensor, which is available at https://github.com/tipfom/ITensorNHDMRG.jl. Using the library is very straightforward and amounts to replacing the cal… --- ## [Understanding the METTS Example Implementation in ITensor](https://itensor.discourse.group/t/understanding-the-metts-example-implementation-in-itensor/2524)
**Author:** [@Ritvik1sharma](https://itensor.discourse.group/u/Ritvik1sharma)\ **Replies:** 1\ **Last updated:** [November 9, 2025, 5:39pm UTC](https://itensor.discourse.group/t/understanding-the-metts-example-implementation-in-itensor/2524 "2025-11-09T17:39:21Z")
Hey I have a question that I am stuck on. I have a problem where the cost function exp(-i beta H) is diagonal i.e. H is created from Z operators only. Plus I have a scenario where I add an extra penalty for some specific… --- ## [Get truncation error when using apply](https://itensor.discourse.group/t/get-truncation-error-when-using-apply/2515)
**Author:** [@davidsmp](https://itensor.discourse.group/u/davidsmp)\ **Replies:** 1\ **Last updated:** [October 24, 2025, 7:17pm UTC](https://itensor.discourse.group/t/get-truncation-error-when-using-apply/2515 "2025-10-24T19:17:17Z")
Hi, I have a basic question about the apply function. I’m using the apply function to apply a set of (two-qubit) unitaries to an MPS, and I’m setting a maximal bond dimension and cutoff. I was wondering if it’s possibl… --- ## [Real time evolution with H(t)](https://itensor.discourse.group/t/real-time-evolution-with-h-t/2413)
**Author:** [@yedi](https://itensor.discourse.group/u/yedi)\ **Replies:** 1\ **Last updated:** [June 11, 2025, 7:50am UTC](https://itensor.discourse.group/t/real-time-evolution-with-h-t/2413 "2025-06-11T07:50:45Z")
Dear professors, I have read this tutorial about MPS time evolution. However, my chain Hamiltonian is time-dependent, for exmaple H(t)=\\sum\_j \\cos (\\omega t)h\_{j,j+1}. Because the Hamiltonians at different times do n… --- ## [Problem using TEBD algorithm to represent Gibbs states](https://itensor.discourse.group/t/problem-using-tebd-algorithm-to-represent-gibbs-states/2356)
**Author:** [@jorgesanseg](https://itensor.discourse.group/u/jorgesanseg)\ **Replies:** 3\ **Last updated:** [May 29, 2025, 9:45am UTC](https://itensor.discourse.group/t/problem-using-tebd-algorithm-to-represent-gibbs-states/2356 "2025-05-29T09:45:25Z")
Hi, I am trying to get thermal states \\rho\_\\beta = e^{-\\beta H} mean values of local observables for long-range interacting system. More concretely the Long Range Spin chain: H\_{\\text{LR, Ising}}= J \\sum\_{i \\neq j}^N… --- ## [Introducing ITensorEntropyTools.jl](https://itensor.discourse.group/t/introducing-itensorentropytools-jl/2192)
**Author:** [@ryanlevy](https://itensor.discourse.group/u/ryanlevy)\ **Replies:** 0\ **Last updated:** [January 6, 2025, 2:01pm UTC](https://itensor.discourse.group/t/introducing-itensorentropytools-jl/2192 "2025-01-06T14:01:39Z")
Introducing a new 3rd party package to compute entanglement entropy ITensorEntropyTools.jl: Features The idea behind ITensorEntropyTools.jl is to automate some common calculations/tools: Entanglement Entropy calcula… --- ## [ERROR: LoadError: UndefVarError: \`checkdone!\` not defined in \`ITensors\`](https://itensor.discourse.group/t/error-loaderror-undefvarerror-checkdone-not-defined-in-itensors/2143)
**Author:** [@yedi](https://itensor.discourse.group/u/yedi)\ **Replies:** 2\ **Last updated:** [November 28, 2024, 9:17am UTC](https://itensor.discourse.group/t/error-loaderror-undefvarerror-checkdone-not-defined-in-itensors/2143 "2024-11-28T09:17:01Z")
Hi, dear developers Recently, I installed ITensor in a new cluster, as following module load anaconda3/5.2.0; pip install jill; jill install add ITensors; add ITensorMPS; add PackageCompiler using ITensors; using Packa… --- ## [\[ANN\] ITensors.jl v0.7 breaking release (MPS/MPO code moved to ITensorMPS.jl)](https://itensor.discourse.group/t/ann-itensors-jl-v0-7-breaking-release-mps-mpo-code-moved-to-itensormps-jl/2089)
**Author:** [@mtfishman](https://itensor.discourse.group/u/mtfishman)\ **Replies:** 0\ **Last updated:** [October 25, 2024, 6:38pm UTC](https://itensor.discourse.group/t/ann-itensors-jl-v0-7-breaking-release-mps-mpo-code-moved-to-itensormps-jl/2089 "2024-10-25T18:38:16Z")
As we forecast in previous announcements, we have released ITensors.jl v0.7. This is a major breaking release because it removes all of the MPS/MPO functionality from ITensors.jl and moves it to ITensorMPS.jl as part of … --- ## [How does DMRG wind up in a different QN symmetry sector](https://itensor.discourse.group/t/how-does-dmrg-wind-up-in-a-different-qn-symmetry-sector/2037)
**Author:** [@corbett5](https://itensor.discourse.group/u/corbett5)\ **Replies:** 2\ **Last updated:** [October 3, 2024, 10:41pm UTC](https://itensor.discourse.group/t/how-does-dmrg-wind-up-in-a-different-qn-symmetry-sector/2037 "2024-10-03T22:41:57Z")
Kind of a philosophical question here: when starting from a state with definite quantum number how does DMRG wind up in a different quantum number sector when quantum number conservation is turned off? Here’s my take: I… --- ## [MPO construction and compression principles (or: how does OpSum work?)](https://itensor.discourse.group/t/mpo-construction-and-compression-principles-or-how-does-opsum-work/1898)
**Author:** [@Qottmann](https://itensor.discourse.group/u/Qottmann)\ **Replies:** 3\ **Last updated:** [July 27, 2024, 3:14pm UTC](https://itensor.discourse.group/t/mpo-construction-and-compression-principles-or-how-does-opsum-work/1898 "2024-07-27T15:14:53Z")
Hello, I am trying to understand what OpSum is doing, and in particular, from a mathematical point of view, how best to construct arbitrary MPOs from sums of tensor products and how to compress them. The way I understa… --- ## [Analytic split of quantum gates as tensor networks in specific cases like Pauli rotations](https://itensor.discourse.group/t/analytic-split-of-quantum-gates-as-tensor-networks-in-specific-cases-like-pauli-rotations/1783)
**Author:** [@Qottmann](https://itensor.discourse.group/u/Qottmann)\ **Replies:** 2\ **Last updated:** [June 5, 2024, 8:58am UTC](https://itensor.discourse.group/t/analytic-split-of-quantum-gates-as-tensor-networks-in-specific-cases-like-pauli-rotations/1783 "2024-06-05T08:58:37Z")
I have a general mathematical / tensor network methods question: I know from a previous discussion that a gate acting on two qubits can be applied to an MPS by turning it into an MPO with identities on the intermediate … --- ## [Finite temperature reference](https://itensor.discourse.group/t/finite-temperature-reference/1773)
**Author:** [@pk123](https://itensor.discourse.group/u/pk123)\ **Replies:** 1\ **Last updated:** [June 2, 2024, 1:07pm UTC](https://itensor.discourse.group/t/finite-temperature-reference/1773 "2024-06-02T13:07:06Z")
Hi everyone, A few weeks ago, I was reading about finite temperature DMRG through this link https://github.com/ITensor/ITensors.jl/tree/main/examples/finite\_temperature where there were example codes for both purificati… --- ## [Applying the Jordan-Wigner String Operator in the Kondo Problem](https://itensor.discourse.group/t/applying-the-jordan-wigner-string-operator-in-the-kondo-problem/1732)
**Author:** [@swanchristmas](https://itensor.discourse.group/u/swanchristmas)\ **Replies:** 3\ **Last updated:** [May 28, 2024, 2:24pm UTC](https://itensor.discourse.group/t/applying-the-jordan-wigner-string-operator-in-the-kondo-problem/1732 "2024-05-28T14:24:02Z")
The string operator F ensures that fermionic operators at different sites anticommute correctly. My question is whether the string operator should be applied even to the Hilbert space of the Kondo spin. Specifically, the… --- ## [\[ANN\] ITensorMPS.jl initial release](https://itensor.discourse.group/t/ann-itensormps-jl-initial-release/1717)
**Author:** [@mtfishman](https://itensor.discourse.group/u/mtfishman)\ **Replies:** 3\ **Last updated:** [May 22, 2024, 2:34pm UTC](https://itensor.discourse.group/t/ann-itensormps-jl-initial-release/1717 "2024-05-22T14:34:37Z")
We are happy to announce the initial release of the ITensorMPS.jl package. This package will be the future home of all of the MPS and MPO functionality currently living in ITensors.jl and ITensorTDVP.jl. For the time be… --- ## [\[ANN\] ITensorTDVP.jl v0.4 release](https://itensor.discourse.group/t/ann-itensortdvp-jl-v0-4-release/1713)
**Author:** [@mtfishman](https://itensor.discourse.group/u/mtfishman)\ **Replies:** 0\ **Last updated:** [May 15, 2024, 1:14am UTC](https://itensor.discourse.group/t/ann-itensortdvp-jl-v0-4-release/1713 "2024-05-15T01:14:40Z")
ITensorTDVP.jl v0.4 has been released. It has many breaking changes to the interface, please see the ITensorTDVP.jl v0.4 release notes for a list of breaking changes and guides on how to upgrade your code. --- ## [How to measure the average value of the magnetic moment Mz in the z-axis direction using metts](https://itensor.discourse.group/t/how-to-measure-the-average-value-of-the-magnetic-moment-mz-in-the-z-axis-direction-using-metts/1703)
**Author:** [@wei](https://itensor.discourse.group/u/wei)\ **Replies:** 1\ **Last updated:** [May 11, 2024, 5:05pm UTC](https://itensor.discourse.group/t/how-to-measure-the-average-value-of-the-magnetic-moment-mz-in-the-z-axis-direction-using-metts/1703 "2024-05-11T17:05:39Z")
Hello everyone, I have encountered a problem in learning the metts method, and I hope to get your help. The original code is as follows: using ITensors using Printf #= This example code implements the minimally entan… --- ## [\[ANN\] Breaking change in ITensorTDVP.jl v0.3](https://itensor.discourse.group/t/ann-breaking-change-in-itensortdvp-jl-v0-3/1684)
**Author:** [@mtfishman](https://itensor.discourse.group/u/mtfishman)\ **Replies:** 0\ **Last updated:** [May 6, 2024, 2:36am UTC](https://itensor.discourse.group/t/ann-breaking-change-in-itensortdvp-jl-v0-3/1684 "2024-05-06T02:36:03Z")
ITensorTDVP.jl v0.3 has a breaking change to the interface of ITensorTDVP.dmrg and ITensorTDVP.dmrg\_x, which now output both the eigenvalue and eigenvector, as opposed to just the eigenvector. See the following for more … --- ## [ITensorTDVP installing error](https://itensor.discourse.group/t/itensortdvp-installing-error/1608)
**Author:** [@Bhargava\_Balaganchi](https://itensor.discourse.group/u/Bhargava_Balaganchi)\ **Replies:** 6\ **Last updated:** [April 2, 2024, 12:57pm UTC](https://itensor.discourse.group/t/itensortdvp-installing-error/1608 "2024-04-02T12:57:05Z")
Hi, I am trying to install ITensorTDVP package to run some calculations of ITensorAGP. However, I am not able to install the package. I am getting the following error : ERROR: LoadError: UndefVarError: check\_hascommoni… --- ## [\[ANN\] Initial release of new ITensor GPU backends](https://itensor.discourse.group/t/ann-initial-release-of-new-itensor-gpu-backends/1227)
**Author:** [@mtfishman](https://itensor.discourse.group/u/mtfishman)\ **Replies:** 9\ **Last updated:** [February 22, 2024, 6:03am UTC](https://itensor.discourse.group/t/ann-initial-release-of-new-itensor-gpu-backends/1227 "2024-02-22T06:03:17Z")
EDIT: For the latest information about GPU support in the Julia version of ITensor, take a look at the documentation page Running on GPUs · ITensors.jl. We are happy to announce an initial release of our new GPU backend… --- ## [\[ANN\] Change to keyword argument behavior in ITensors.jl](https://itensor.discourse.group/t/ann-change-to-keyword-argument-behavior-in-itensors-jl/1258)
**Author:** [@mtfishman](https://itensor.discourse.group/u/mtfishman)\ **Replies:** 5\ **Last updated:** [February 13, 2024, 8:51pm UTC](https://itensor.discourse.group/t/ann-change-to-keyword-argument-behavior-in-itensors-jl/1258 "2024-02-13T20:51:24Z")
As of ITensors.jl v0.3.49, functions like dmrg, factorize, and svd are stricter about how they handle keyword arguments. Specifically, if you pass unsupported keyword arguments to them, they will now error instead of sil… --- ## [Does ITensor welcome links to open source libraries based on ITensor?](https://itensor.discourse.group/t/does-itensor-welcome-links-to-open-source-libraries-based-on-itensor/741)
**Author:** [@haggaila](https://itensor.discourse.group/u/haggaila)\ **Replies:** 10\ **Last updated:** [December 20, 2023, 10:05am UTC](https://itensor.discourse.group/t/does-itensor-welcome-links-to-open-source-libraries-based-on-itensor/741 "2023-12-20T10:05:10Z")
Hi, I wish to ask whether you currently support/agree to post links to open source packages based on ITensor, perhaps in the Community Codes section of the Codes page? If so, what would be the way to proceed with reque… --- ## [ITensor on GPU and conserved Quantum numbers](https://itensor.discourse.group/t/itensor-on-gpu-and-conserved-quantum-numbers/1234)
**Author:** [@melina](https://itensor.discourse.group/u/melina)\ **Replies:** 5\ **Last updated:** [October 19, 2023, 10:34pm UTC](https://itensor.discourse.group/t/itensor-on-gpu-and-conserved-quantum-numbers/1234 "2023-10-19T22:34:51Z")
Last year, a question was asked about conserved quantum numbers and calculation on GPU: Error with conserved quantum numbers and ITensorGPU The answer was that this was not yet implemented then. I am now running ITenso… --- ## [Drawing the T-h diagram from T dependent m-h curves](https://itensor.discourse.group/t/drawing-the-t-h-diagram-from-t-dependent-m-h-curves/617)
**Author:** [@Explorer](https://itensor.discourse.group/u/Explorer)\ **Replies:** 5\ **Last updated:** [October 18, 2023, 4:49pm UTC](https://itensor.discourse.group/t/drawing-the-t-h-diagram-from-t-dependent-m-h-curves/617 "2023-10-18T16:49:11Z")
Following is the m-h curve at various temperatures for a spin chain model. It can be seen that m=1/3 magnetization plateau disappears at T=0.3 J\_1. From this data I wanted to draw T-h phase diagram showing the disappear… --- ## [How closely/exactly we can model the quasi 1D spin chain compound using the corresponding 1D spin chain model (effective hamiltonian) for it?](https://itensor.discourse.group/t/how-closely-exactly-we-can-model-the-quasi-1d-spin-chain-compound-using-the-corresponding-1d-spin-chain-model-effective-hamiltonian-for-it/1132)
**Author:** [@Explorer](https://itensor.discourse.group/u/Explorer)\ **Replies:** 0\ **Last updated:** [September 1, 2023, 4:36pm UTC](https://itensor.discourse.group/t/how-closely-exactly-we-can-model-the-quasi-1d-spin-chain-compound-using-the-corresponding-1d-spin-chain-model-effective-hamiltonian-for-it/1132 "2023-09-01T16:36:56Z")
This ques might not fit to ‘itensor’, but it is an important question needs to be addressed. I was wondering how closely we can write/model the 1D (lets say ) spin chain hamiltonian corresponding to quasi 1D spin chain… [Next page](https://itensor.discourse.group/c/general/9.md?page=1)