# Catalyst **URL:** https://discuss.pennylane.ai/c/catalyst/22.md [Latest](https://discuss.pennylane.ai/latest.md) · [Categories](https://discuss.pennylane.ai/categories.md) --- ## [About the Catalyst category](https://discuss.pennylane.ai/t/about-the-catalyst-category/3078)
**Author:** [@isaacdevlugt](https://discuss.pennylane.ai/u/isaacdevlugt)\ **Replies:** 0
For all posts related to Catalyst, the package that enables just-in-time (JIT) compilation of PennyLane programs. This includes usage, help, and development. See the Catalyst GitHub (https://github.com/pennylaneai/cataly… --- ## [Subject: Bypassing std::vector re-allocation in Catalyst Lightning C++ backend via custom CXL/L3 pointers?](https://discuss.pennylane.ai/t/subject-bypassing-std-vector-re-allocation-in-catalyst-lightning-c-backend-via-custom-cxl-l3-pointers/9544)
**Author:** [@Jang\_Peter](https://discuss.pennylane.ai/u/Jang_Peter)\ **Replies:** 7\ **Last updated:** [October 20, 2026, 11:03am UTC](https://discuss.pennylane.ai/t/subject-bypassing-std-vector-re-allocation-in-catalyst-lightning-c-backend-via-custom-cxl-l3-pointers/9544 "2026-10-20T11:03:22Z")
Hi Catalyst Team, We are benchmarking ultra-low-latency execution pipelines for high-dimensional state vectors in Catalyst (v0.18+). Currently, the Lightning C++ backend re-allocates state vectors via standard heap all… --- ## [Overusing Catalyst callbacks](https://discuss.pennylane.ai/t/overusing-catalyst-callbacks/9284)
**Author:** [@sergeimironov](https://discuss.pennylane.ai/u/sergeimironov)\ **Replies:** 2\ **Last updated:** [March 20, 2026, 10:24am UTC](https://discuss.pennylane.ai/t/overusing-catalyst-callbacks/9284 "2026-03-20T10:24:38Z")
Hihi! I’m exploring an application for Catalyst callbacks where I need to call a Python function that doesn’t particularly fit into the ‘pure\_callback’ requirement from the docs. Concretely, my function accesses a global… --- ## [Error when using catalyst.grad with BlockEncode](https://discuss.pennylane.ai/t/error-when-using-catalyst-grad-with-blockencode/9234)
**Author:** [@kinianlo](https://discuss.pennylane.ai/u/kinianlo)\ **Replies:** 1\ **Last updated:** [February 2, 2026, 7:38pm UTC](https://discuss.pennylane.ai/t/error-when-using-catalyst-grad-with-blockencode/9234 "2026-02-02T19:38:38Z")
I am encountering a TracerArrayConversionError when trying to compute the gradient of a QNode that utilizes qml.BlockEncode inside a catalyst.qjit compiled function. Example: import pennylane as qml import catalyst fro… --- ## [Hybrid Jax Model: JIT gradient computation error](https://discuss.pennylane.ai/t/hybrid-jax-model-jit-gradient-computation-error/9205)
**Author:** [@minn-bj](https://discuss.pennylane.ai/u/minn-bj)\ **Replies:** 6\ **Last updated:** [February 2, 2026, 9:20am UTC](https://discuss.pennylane.ai/t/hybrid-jax-model-jit-gradient-computation-error/9205 "2026-02-02T09:20:37Z")
Hello there, I have an Issue with the jit computation if gradients in a (in principle) hybrid model using Jax and Catalyst. The following ends up with an error regarding the compiler (I guess). Is there some advice wha… --- ## [Issue setting up-to-date environment with Catalyst](https://discuss.pennylane.ai/t/issue-setting-up-to-date-environment-with-catalyst/9076)
**Author:** [@salvozamm](https://discuss.pennylane.ai/u/salvozamm)\ **Replies:** 4\ **Last updated:** [October 15, 2025, 5:42pm UTC](https://discuss.pennylane.ai/t/issue-setting-up-to-date-environment-with-catalyst/9076 "2025-10-15T17:42:48Z")
Hi everyone, I would like to ask for you help about the catalyst initial setup. I am relatively new to Pennylane, and so far I have been using it either on its own, or with lightning plugins and jax workflows, with ever… --- ## [Parallel vectorized circuit execution with vmap](https://discuss.pennylane.ai/t/parallel-vectorized-circuit-execution-with-vmap/8370)
**Author:** [@LasradoRohan](https://discuss.pennylane.ai/u/LasradoRohan)\ **Replies:** 9\ **Last updated:** [August 25, 2025, 3:06pm UTC](https://discuss.pennylane.ai/t/parallel-vectorized-circuit-execution-with-vmap/8370 "2025-08-25T15:06:50Z")
Hi, My use case requires me to execute the same simple parameterized circuit over few qubits (~9) over a batch of inputs (~10,000 unique inputs to the circuit for a minimal POC). Naturally, I have tried to achieve this… --- ## [Installing jax-cuda, pennylane-catalyst with Pytorch?](https://discuss.pennylane.ai/t/installing-jax-cuda-pennylane-catalyst-with-pytorch/8850)
**Author:** [@ashutiw2k](https://discuss.pennylane.ai/u/ashutiw2k)\ **Replies:** 7\ **Last updated:** [August 8, 2025, 7:10pm UTC](https://discuss.pennylane.ai/t/installing-jax-cuda-pennylane-catalyst-with-pytorch/8850 "2025-08-08T19:10:25Z")
Hello, I am trying to use a Pytorch model along with my quantum circuit accelerated by catalyst. Initially, I ran the command: pip install pennylane pennylane-lightning-gpu pennylane-catalyst pennylane-qiskit torch T… --- ## [Compiler crash while computing circuit gradient (qjit and vmap) with lightning.qubit and lightning.kokkos](https://discuss.pennylane.ai/t/compiler-crash-while-computing-circuit-gradient-qjit-and-vmap-with-lightning-qubit-and-lightning-kokkos/8773)
**Author:** [@minn-bj](https://discuss.pennylane.ai/u/minn-bj)\ **Replies:** 5\ **Last updated:** [July 18, 2025, 7:43pm UTC](https://discuss.pennylane.ai/t/compiler-crash-while-computing-circuit-gradient-qjit-and-vmap-with-lightning-qubit-and-lightning-kokkos/8773 "2025-07-18T19:43:22Z")
Hello there, I have an issue computing the ‘jit-ed’ and ‘vmap-ed’ gradient of a circuit. It seems that the compiler is crashing for some reason I do not understand. A minimal example and some further information are wri… --- ## [cuda\_quantum compiler not found: 'PackageNotFoundError: No package metadata was found for cuda\_quantum'](https://discuss.pennylane.ai/t/cuda-quantum-compiler-not-found-packagenotfounderror-no-package-metadata-was-found-for-cuda-quantum/8670)
**Author:** [@minn-bj](https://discuss.pennylane.ai/u/minn-bj)\ **Replies:** 5\ **Last updated:** [July 18, 2025, 6:13pm UTC](https://discuss.pennylane.ai/t/cuda-quantum-compiler-not-found-packagenotfounderror-no-package-metadata-was-found-for-cuda-quantum/8670 "2025-07-18T18:13:56Z")
Hello there, I was trying to use the cuda\_quantum compiler in combination with jax qjit. Unfortunately, pennnylane can’t find the cuda\_quantum package even though it is installed via ‘pip install cudaq’ (cuda\_quantum do… --- ## [Integrating Catalyst QIR - CUDA for Quantum Algo challenge](https://discuss.pennylane.ai/t/integrating-catalyst-qir-cuda-for-quantum-algo-challenge/8594)
**Author:** [@D\_Karli](https://discuss.pennylane.ai/u/D_Karli)\ **Replies:** 12\ **Last updated:** [July 3, 2025, 6:42pm UTC](https://discuss.pennylane.ai/t/integrating-catalyst-qir-cuda-for-quantum-algo-challenge/8594 "2025-07-03T18:42:10Z")
We are designing a challenge where innovator submit their circuits for pre-image search for keccak-256 4-round hash. We are aiming to get clear benchmarks for cryptanalysis and incentives algorithmic innovation. We are r… --- ## [MLIR extraction for custom circuit](https://discuss.pennylane.ai/t/mlir-extraction-for-custom-circuit/4700)
**Author:** [@quantum-girl](https://discuss.pennylane.ai/u/quantum-girl)\ **Replies:** 8\ **Last updated:** [May 22, 2025, 7:01pm UTC](https://discuss.pennylane.ai/t/mlir-extraction-for-custom-circuit/4700 "2025-05-22T19:01:35Z")
Dear Community, I am new to the Catalyst package and I am currently on learning curve. I have been going through the documentation to understand the Catalyst better. At the page Catalyst Compiler Passes — Catalyst 0.6.0… --- ## [Pennylane-lightning dev dependency in Catalyst build](https://discuss.pennylane.ai/t/pennylane-lightning-dev-dependency-in-catalyst-build/8057)
**Author:** [@n-io](https://discuss.pennylane.ai/u/n-io)\ **Replies:** 2\ **Last updated:** [February 28, 2025, 7:19pm UTC](https://discuss.pennylane.ai/t/pennylane-lightning-dev-dependency-in-catalyst-build/8057 "2025-02-28T19:19:00Z")
Hi there, I’m trying to follow the minimal building from source guide for MacOS, but am running into build errors. Specifically, there appears to be a dependency on pennylane-lightning==0.41.0-dev22, and it’s not entire… --- ## [Catalyst compilation failure: operand #1 does not dominate this use](https://discuss.pennylane.ai/t/catalyst-compilation-failure-operand-1-does-not-dominate-this-use/4239)
**Author:** [@schance995](https://discuss.pennylane.ai/u/schance995)\ **Replies:** 9\ **Last updated:** [January 22, 2025, 1:25pm UTC](https://discuss.pennylane.ai/t/catalyst-compilation-failure-operand-1-does-not-dominate-this-use/4239 "2025-01-22T13:25:07Z")
Hi! I’m trying out the QML optimization with Jax tutorial: How to optimize a QML model using JAX and Optax | PennyLane Demos This code snippet is the same as the tutorial, except that I use lightning.qubit and catalyst … --- ## [Trouble calling QJIT compiled QNode inside a nnx.jit compiled flax.nnx.Module](https://discuss.pennylane.ai/t/trouble-calling-qjit-compiled-qnode-inside-a-nnx-jit-compiled-flax-nnx-module/7853)
**Author:** [@LasradoRohan](https://discuss.pennylane.ai/u/LasradoRohan)\ **Replies:** 4\ **Last updated:** [January 16, 2025, 4:18pm UTC](https://discuss.pennylane.ai/t/trouble-calling-qjit-compiled-qnode-inside-a-nnx-jit-compiled-flax-nnx-module/7853 "2025-01-16T16:18:44Z")
Hi, I’m trying to “package” a Catalyst (qjit) compiled circuit within a flax.nnx.Module for easy management of weights. However, the tracer passed by NNX is rejected by the QJIT function. Error: TypeError: Value Trac… --- ## [MLIR Pass Rewriting](https://discuss.pennylane.ai/t/mlir-pass-rewriting/7714)
**Author:** [@patelvyom](https://discuss.pennylane.ai/u/patelvyom)\ **Replies:** 4\ **Last updated:** [December 12, 2024, 5:04pm UTC](https://discuss.pennylane.ai/t/mlir-pass-rewriting/7714 "2024-12-12T17:04:56Z")
I am trying to implement a CNOT-propagation Pass in MLIR in Catalyst. An example .mlir is as follows: module { func.func @my\_circuit( ) -\> (!quantum.bit, !quantum.bit) { %0 = quantum.alloc( 2) : !quantum.reg %… --- ## [Memory leak upon switching from jax.jit to catalyst.qjit](https://discuss.pennylane.ai/t/memory-leak-upon-switching-from-jax-jit-to-catalyst-qjit/7468)
**Author:** [@Sachin\_Reddy](https://discuss.pennylane.ai/u/Sachin_Reddy)\ **Replies:** 6\ **Last updated:** [November 13, 2024, 4:53pm UTC](https://discuss.pennylane.ai/t/memory-leak-upon-switching-from-jax-jit-to-catalyst-qjit/7468 "2024-11-13T16:53:51Z")
Hi there! I’m trying to use Pennylane-Catalyst to speedup training of my pennylane-jax based quantum-classical QLSTM for time-series prediction. With jax’s jit decorator, the code doesn’t have any issue, however it’s q… --- ## [Catalyst for QAOA](https://discuss.pennylane.ai/t/catalyst-for-qaoa/5300)
**Author:** [@Bach\_Bao](https://discuss.pennylane.ai/u/Bach_Bao)\ **Replies:** 4\ **Last updated:** [October 2, 2024, 2:17pm UTC](https://discuss.pennylane.ai/t/catalyst-for-qaoa/5300 "2024-10-02T14:17:57Z")
Hi there, It has been a while since my last touch with Pennylane and Catalyst, and now I want to use Catalyst as a way to speed up QAOA optimization but I am running into some issues that I hope to get help with… My pe… --- ## [Integrating Catalyst with PyTorch](https://discuss.pennylane.ai/t/integrating-catalyst-with-pytorch/4404)
**Author:** [@justin6626](https://discuss.pennylane.ai/u/justin6626)\ **Replies:** 5\ **Last updated:** [May 2, 2024, 2:37pm UTC](https://discuss.pennylane.ai/t/integrating-catalyst-with-pytorch/4404 "2024-05-02T14:37:49Z")
Hi all, I am working on a quantum machine learning project written in Pytorch and Pennylane, but I would like to try to use Pennylane-Catalyst to speed up the training process. My specs are as follows: Name: PennyLane… --- ## [Non-commuting observables with Catalyst](https://discuss.pennylane.ai/t/non-commuting-observables-with-catalyst/4328)
**Author:** [@idnm](https://discuss.pennylane.ai/u/idnm)\ **Replies:** 4\ **Last updated:** [March 22, 2024, 8:27pm UTC](https://discuss.pennylane.ai/t/non-commuting-observables-with-catalyst/4328 "2024-03-22T20:27:28Z")
Hi! Firstly, thanks for an excellent piece of software. I recently started using pennylane more, and enjoying it. Here is a problem I’m trying to solve. I have a deep circuit composed of identical layers with different … --- ## [Error in running Catalyst as no compiler found](https://discuss.pennylane.ai/t/error-in-running-catalyst-as-no-compiler-found/4245)
**Author:** [@Bach\_Bao](https://discuss.pennylane.ai/u/Bach_Bao)\ **Replies:** 6\ **Last updated:** [March 20, 2024, 3:02pm UTC](https://discuss.pennylane.ai/t/error-in-running-catalyst-as-no-compiler-found/4245 "2024-03-20T15:02:01Z")
Hi there, I have installed PennyLane catalyst on an Honda virtual environment on my university’s cluster. It kinda weird to me that for some nodes, Catalyst run perfectly fine. However, for some other nodes, I always fa… --- ## [Error installing catalyst](https://discuss.pennylane.ai/t/error-installing-catalyst/3938)
**Author:** [@Bach\_Bao](https://discuss.pennylane.ai/u/Bach_Bao)\ **Replies:** 2\ **Last updated:** [March 8, 2024, 5:07pm UTC](https://discuss.pennylane.ai/t/error-installing-catalyst/3938 "2024-03-08T17:07:10Z")
Hi, I am trying to install Catalyst but having problem with the jaxlib version. The error that I am having is Collecting pennylane-catalyst Using cached pennylane\_catalyst-0.1.2-py3-none-manylinux2014\_x86\_64.whl (62.… --- ## [Error running make test targets in frontend for Catalyst](https://discuss.pennylane.ai/t/error-running-make-test-targets-in-frontend-for-catalyst/3369)
**Author:** [@ndcroos](https://discuss.pennylane.ai/u/ndcroos)\ **Replies:** 11\ **Last updated:** [September 6, 2023, 8:01pm UTC](https://discuss.pennylane.ai/t/error-running-make-test-targets-in-frontend-for-catalyst/3369 "2023-09-06T20:01:45Z")
Hi, I am trying to make a first contribution to Catalyst, in test\_template.py in frontend. I am following the installing guide of catalyst. I am running in the directory catalyst. I am not sure if I am running the comm… --- ## [Extending Operation with QJIT](https://discuss.pennylane.ai/t/extending-operation-with-qjit/3100)
**Author:** [@Nikhil\_Narayanan](https://discuss.pennylane.ai/u/Nikhil_Narayanan)\ **Replies:** 17\ **Last updated:** [July 4, 2023, 1:23pm UTC](https://discuss.pennylane.ai/t/extending-operation-with-qjit/3100 "2023-07-04T13:23:49Z")
This is the contents of a file that I’m trying to import, import pennylane as qml from catalyst import qjit from pennylane.numpy import pi, tensor from pennylane.operation import Operation class StronglyEntanglingLaye… --- ## [Pennylane Catalyst OS-Error: All available compiler options exhausted](https://discuss.pennylane.ai/t/pennylane-catalyst-os-error-all-available-compiler-options-exhausted/3077)
**Author:** [@Nikhil\_Narayanan](https://discuss.pennylane.ai/u/Nikhil_Narayanan)\ **Replies:** 3\ **Last updated:** [June 21, 2023, 1:51pm UTC](https://discuss.pennylane.ai/t/pennylane-catalyst-os-error-all-available-compiler-options-exhausted/3077 "2023-06-21T13:51:18Z")
Hi, I’m trying to demo the JIT functionality provided by catalyst as in the Catalyst Runtime — Catalyst 0.2.0-dev documentation from catalyst import qjit, measure, cond, for\_loop, while\_loop import pennylane as qml from…