ITensor/ITensorMPS.jl

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MPS and MPO methods based on ITensor (ITensors.jl). ITensorMPS.jl is supported by the Simons Foundation's Flatiron Institute.

Stars: 85
Forks: 27
Open beginner issues: 0
Indexed issues: 74
Avg merge: 22m
Merged PRs (30d): 1

Dominant language: Julia
License: Apache-2.0
Last GitHub push: Sep 9, 2026
Latest indexed: Sep 20, 2026
Contributing guide: No contributing guide
Code of conduct: No code of conduct
Beginner labels: No beginner labels indexed

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74 open issues indexed

ITensorMPS and CUDA.jl Duplication / Erroneous Memory Allocations in DMRG Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#209 · 1 reaction · Opened Apr 22, 2026
[BUG] Vector of MPOs in DMRG works for the ground state, but it does not work for the excited states. Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 65/100

ITensor/ITensorMPS.jl#207 · Opened Apr 14, 2026
[BUG] write_when_maxdim_exceeds not working for TDVP Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 42/100

ITensor/ITensorMPS.jl#176 · Opened Feb 20, 2026
Typo in definition of "Adagdn" for ElecK site type in the example Open

bug

Difficulty 1/5 Under an hour Newbie friendliness 58/100

ITensor/ITensorMPS.jl#175 · Opened Feb 16, 2026
Problem with TEBD on Fermi-Hubbard model with Electron indices Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#159 · 1 reaction · Opened Oct 6, 2025
[ENHANCEMENT] Have `op_term(::Tuple{Number})` return the identity Open

enhancement

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

ITensor/ITensorMPS.jl#154 · Opened Aug 19, 2025
[ENHANCEMENT] OpSum term to ITensor Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 45/100

ITensor/ITensorMPS.jl#150 · 1 comment · Opened Aug 4, 2025
[BUG] write_when_maxdim_exceeds not working for excited state dmrg calculation Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 50/100

ITensor/ITensorMPS.jl#145 · Opened Jun 13, 2025
[BUG] Misleading presence of `normalize` keyword in `orthogonalize!` Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#140 · 4 comments · Opened Apr 16, 2025
[BUG] Fail to add noise to TDVP Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 45/100

ITensor/ITensorMPS.jl#130 · 1 comment · Opened Mar 25, 2025
Strange numerical issue when making an MPS, works fine on Linux, Nan issues on Mac Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

ITensor/ITensorMPS.jl#110 · 15 comments · Opened Jan 23, 2025
Issue in mps.jl file, line 899 Open

Difficulty 1/5 Under an hour Newbie friendliness 55/100

ITensor/ITensorMPS.jl#105 · 3 comments · Opened Dec 24, 2024
[BUG] ChainRule for norm function Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#95 · 4 comments · Opened Nov 18, 2024
Issue running Trotter-Suzuki example Open

Difficulty 3/5 1-2 days Newbie friendliness 32/100

ITensor/ITensorMPS.jl#90 · 2 comments · Opened Oct 29, 2024
Implement local subspace expansion Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

ITensor/ITensorMPS.jl#41 · Opened Oct 25, 2024
Set `eager=true` in `exponentiate` backend Open

Difficulty 2/5 1-3 hours Newbie friendliness 38/100

ITensor/ITensorMPS.jl#40 · Opened Oct 18, 2024
[ITensorMPS] [BUG] Default algorithm for adding MPSs leading to large bond dimensions Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 45/100

ITensor/ITensorMPS.jl#86 · 11 comments · Opened Oct 14, 2024
dmrg_x does not support write to disk Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#25 · 2 comments · Opened Aug 28, 2024
[ITensors] [BUG] Itensors refuses "weight" argument to DMRG Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 25/100

ITensor/ITensorMPS.jl#89 · 3 comments · Opened Aug 6, 2024
[ITensors] [ENHANCEMENT] Expose `ConvergenceInfo` in calls to KrylovKit methods Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 38/100

ITensor/ITensorMPS.jl#88 · Opened Jul 10, 2024
[ENHANCEMENT] Expose `truncerr` in calls to `truncate!` Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#96 · 4 comments · Opened Jul 2, 2024
Test GPU compatibility using JLArrays Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#39 · Opened Jun 20, 2024
Add support for running examples on GPU and test on GPU Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#23 · 1 comment · Opened Jun 2, 2024
Sparse diagonalization methods for getting the relevant spectrum of the projected Hamiltonian? Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

ITensor/ITensorMPS.jl#38 · 1 comment · Opened May 6, 2024
[ITensors] [BUG] `add(::MPS, ::MPS; alg="directsum")` broken for mismatched arrow directions Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 25/100

ITensor/ITensorMPS.jl#85 · Opened Feb 21, 2024
[ITensors] [BUG] Bad performance of DMRG in AMD CPU Open

bug

ITensor/ITensorMPS.jl#84 · 4 comments · 1 assignee · Opened Jan 3, 2024
[ITensors] [BUG] Sum of MPOs in DMRG for excited states doesn't work Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#83 · 2 comments · Opened Dec 16, 2023
[ITensors] [BUG] Issue running TEBD on CUDA GPU with single precision Open

bug

ITensor/ITensorMPS.jl#82 · 1 comment · 1 assignee · Opened Nov 16, 2023
[NDTensors] [BUG] Bug running DMRG on Metal with small cutoffs and large bond dimensions Open

bug

ITensor/ITensorMPS.jl#87 · 1 assignee · Opened Nov 16, 2023
[ITensors] [ENHANCEMENT] DMRG with nonzero primes on MPO link indices Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#81 · Opened Nov 16, 2023
[ITensors] [ENHANCEMENT] Faster Computing Gradients of Variational Circuits with Hardware-Efficient Ansatz Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 25/100

ITensor/ITensorMPS.jl#80 · Opened Jun 30, 2023
Generalizing fitting algorithm to MPO-MPO multiplication Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

ITensor/ITensorMPS.jl#37 · 7 comments · 1 reaction · Opened Nov 21, 2022
tdvp_order throws an error for order 4 Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#36 · 4 comments · 1 reaction · Opened Nov 7, 2022
linsolve unstable under repeated application Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#35 · Opened Oct 26, 2022
[ITensors] [BUG] logdot and lognorm are not compatible with AD due to try/catch Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#77 · 1 comment · Opened Oct 21, 2022
[ITensors] Reducing allocations in contraction (or `inner`) Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

ITensor/ITensorMPS.jl#78 · 1 comment · Opened Oct 10, 2022
[ITensors] [BUG] Sum of MPS involving link dimension zero fails. Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 45/100

ITensor/ITensorMPS.jl#76 · Opened Jun 16, 2022
[ITensors] [ENHANCEMENT] Easy padding of an MPS to a desired bond dimension. Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#75 · Opened Jun 16, 2022
[ITensors] [BUG] maxlinkdim(MPS(sinds; linkdims=0)) returns 1 Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#74 · Opened Jun 16, 2022
[ITensors] [BUG] Automatic differentiation Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#73 · 4 comments · Opened Jun 3, 2022
[ITensors] [BUG] QN error when applying MPO to MPS Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 42/100

ITensor/ITensorMPS.jl#72 · 4 comments · Opened May 19, 2022
[ITensors] [BUG] Add check for flux when adding ITensors and MPS Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 45/100

ITensor/ITensorMPS.jl#71 · 1 reaction · Opened Apr 29, 2022
[ITensors] [ENHANCEMENT] Passing site-dependent keyword arguments to `siteinds` Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 48/100

ITensor/ITensorMPS.jl#70 · Opened Mar 29, 2022
[ITensors] [BUG] `randomMPS` doesn't return MPS with minimal bond dimension on the boundaries Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 42/100

ITensor/ITensorMPS.jl#69 · 2 comments · Opened Mar 17, 2022
[ITensors] [ENHANCEMENT] Support for Trotterizing time dependent operators Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 35/100

ITensor/ITensorMPS.jl#68 · Opened Mar 14, 2022
[ITensors] [ENHANCEMENT] Integrate with `Observers.jl` Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 45/100

ITensor/ITensorMPS.jl#67 · 3 comments · Opened Mar 9, 2022
[ITensors] [ENHANCEMENT] AD `rrules` Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 25/100

ITensor/ITensorMPS.jl#66 · Opened Mar 9, 2022
Reuse Projected Hamiltonian Tensors Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

ITensor/ITensorMPS.jl#34 · 9 comments · Opened Mar 9, 2022
Test noise term Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

ITensor/ITensorMPS.jl#33 · 4 comments · Opened Mar 4, 2022
`productMPS` not differentiable Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 35/100

ITensor/ITensorMPS.jl#65 · 2 comments · Opened Nov 22, 2021

ITensor/ITensorMPS.jl

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