# Latest **URL:** https://discuss.pennylane.ai/latest.md?page=2 [Latest](https://discuss.pennylane.ai/latest.md) · [Categories](https://discuss.pennylane.ai/categories.md) **Page:** 3 --- ## [The new PennyLane Codebook is here!](https://discuss.pennylane.ai/t/the-new-pennylane-codebook-is-here/4595)
**Author:** [@discourse-admin](https://discuss.pennylane.ai/u/discourse-admin)\ **Replies:** 2\ **Last updated:** [May 27, 2026, 12:23am UTC](https://discuss.pennylane.ai/t/the-new-pennylane-codebook-is-here/4595 "2026-05-27T00:23:33Z")
Meet the new Codebook! Learn quantum computing with PennyLane — the leading tool for programming quantum computers. Share your feedback about the new Codebook here! --- ## [PennyLane x unitaryHACK2026 challenge](https://discuss.pennylane.ai/t/pennylane-x-unitaryhack2026-challenge/9345)
**Author:** [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\ **Replies:** 0\ **Last updated:** [May 26, 2026, 4:01am UTC](https://discuss.pennylane.ai/t/pennylane-x-unitaryhack2026-challenge/9345 "2026-05-26T04:01:00Z")
Use this topic to ask your questions about the PennyLane x unitaryHACK2026 challenge. You can earn an exclusive, time-limited badge for completing it! --- ## [What does "Error '00' mean?](https://discuss.pennylane.ai/t/what-does-error-00-mean/9347)
**Author:** [@fyellin](https://discuss.pennylane.ai/u/fyellin)\ **Replies:** 5\ **Last updated:** [May 25, 2026, 5:51pm UTC](https://discuss.pennylane.ai/t/what-does-error-00-mean/9347 "2026-05-25T17:51:54Z")
I’m running PF.5.1. My code runs. I get the printed output: the success probability is 0.2524 which is roughly what I expected but then above that I see a red stripe above my user output with the message Error '00'. … --- ## [Codebook: Variational Quantum Eigensolver](https://discuss.pennylane.ai/t/codebook-variational-quantum-eigensolver/7224)
**Author:** [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\ **Replies:** 9\ **Last updated:** [May 19, 2026, 4:34pm UTC](https://discuss.pennylane.ai/t/codebook-variational-quantum-eigensolver/7224 "2026-05-19T16:34:43Z")
Ask here about the “Variational Quantum Eigensolver” Codebook topic from the “Introduction to Variational Quantum Algorithms” module. --- ## [Codercise G.5.1 - Preparing a multi-solution oracle](https://discuss.pennylane.ai/t/codercise-g-5-1-preparing-a-multi-solution-oracle/9335)
**Author:** [@delacroissant](https://discuss.pennylane.ai/u/delacroissant)\ **Replies:** 1\ **Last updated:** [May 13, 2026, 4:10pm UTC](https://discuss.pennylane.ai/t/codercise-g-5-1-preparing-a-multi-solution-oracle/9335 "2026-05-13T16:10:11Z")
In Codercise G.5.1 it is written: Let’s start by coding up this new oracle. Create an oracle for a random solution set of a given size using the MultiControlledX gate. Remember that this takes a string for control\_value… --- ## [Small typo in Codercise F.1.3 - The nearest power of 2](https://discuss.pennylane.ai/t/small-typo-in-codercise-f-1-3-the-nearest-power-of-2/9336)
**Author:** [@delacroissant](https://discuss.pennylane.ai/u/delacroissant)\ **Replies:** 2\ **Last updated:** [May 13, 2026, 7:23am UTC](https://discuss.pennylane.ai/t/small-typo-in-codercise-f-1-3-the-nearest-power-of-2/9336 "2026-05-13T07:23:37Z")
There is a small typo in the firsy hint in Codercise F.1.3. The text says: Let’s look at simple example, we want to find the nearest power of 2 of x = 16 (which is 16, of course). but instead it should say: “which i… --- ## [PennyLane v0.45 Challenge: Resource Estimation](https://discuss.pennylane.ai/t/pennylane-v0-45-challenge-resource-estimation/9337)
**Author:** [@dren](https://discuss.pennylane.ai/u/dren)\ **Replies:** 0\ **Last updated:** [May 12, 2026, 4:40pm UTC](https://discuss.pennylane.ai/t/pennylane-v0-45-challenge-resource-estimation/9337 "2026-05-12T16:40:55Z")
Use this topic to ask your questions about the PennyLane Challenge: Introduction to Resource Estimation. You can earn a badge for completing it! --- ## [Regarding the lecture of pennylane](https://discuss.pennylane.ai/t/regarding-the-lecture-of-pennylane/9321)
**Author:** [@ajcodes](https://discuss.pennylane.ai/u/ajcodes)\ **Replies:** 3\ **Last updated:** [May 8, 2026, 1:32am UTC](https://discuss.pennylane.ai/t/regarding-the-lecture-of-pennylane/9321 "2026-05-08T01:32:19Z")
Hi @CatalinaAlbornoz, I’ve been following your lectures on PennyLane via the Wiser platform and found them incredibly insightful. The way you bridge the gap between quantum theory and differentiable programming is amazi… --- ## [Training QSP Phase Angles Directly with Gradient Descent](https://discuss.pennylane.ai/t/training-qsp-phase-angles-directly-with-gradient-descent/9320)
**Author:** [@rosspeili](https://discuss.pennylane.ai/u/rosspeili)\ **Replies:** 1\ **Last updated:** [April 30, 2026, 6:31pm UTC](https://discuss.pennylane.ai/t/training-qsp-phase-angles-directly-with-gradient-descent/9320 "2026-04-30T18:31:07Z")
Quantum Signal Processing (QSP) is one of those beautiful algorithms that promises to turn a few qubits and some carefully chosen rotation angles into useful polynomial transformations. It’s a foundational block for Hami… --- ## [Availability of qrackbind for PennyLane](https://discuss.pennylane.ai/t/availability-of-qrackbind-for-pennylane/9319)
**Author:** [@stokomax](https://discuss.pennylane.ai/u/stokomax)\ **Replies:** 1\ **Last updated:** [April 29, 2026, 9:17pm UTC](https://discuss.pennylane.ai/t/availability-of-qrackbind-for-pennylane/9319 "2026-04-29T21:17:04Z")
Hello! I am seeking feedback and a few brave souls to test a new Qrack python binding package called qrackbind. The package includes a few PennyLane devices which are discussed in the README. As noted in the project REA… --- ## [An issue in the FALQON demo](https://discuss.pennylane.ai/t/an-issue-in-the-falqon-demo/9290)
**Author:** [@adityab](https://discuss.pennylane.ai/u/adityab)\ **Replies:** 5\ **Last updated:** [April 27, 2026, 9:55pm UTC](https://discuss.pennylane.ai/t/an-issue-in-the-falqon-demo/9290 "2026-04-27T21:55:55Z")
Hi all, I am a new user of Pennylane and the awesome set of demos have been really helpful to get me started. This post is about the demo on feedback-assisted quantum optimization (FALQON). There seem to be a couple of… --- ## [Access to Xanadu's Quantum hardware](https://discuss.pennylane.ai/t/access-to-xanadus-quantum-hardware/9317)
**Author:** [@gopalsahu](https://discuss.pennylane.ai/u/gopalsahu)\ **Replies:** 1\ **Last updated:** [April 22, 2026, 6:46pm UTC](https://discuss.pennylane.ai/t/access-to-xanadus-quantum-hardware/9317 "2026-04-22T18:46:54Z")
How can we access Xanadu’s Quantum hardware for academic research ? --- ## [Non-monotonic realization error in hamiltonian simulation of qubitized operator with GQSP](https://discuss.pennylane.ai/t/non-monotonic-realization-error-in-hamiltonian-simulation-of-qubitized-operator-with-gqsp/9303)
**Author:** [@incud](https://discuss.pennylane.ai/u/incud)\ **Replies:** 3\ **Last updated:** [April 16, 2026, 3:35pm UTC](https://discuss.pennylane.ai/t/non-monotonic-realization-error-in-hamiltonian-simulation-of-qubitized-operator-with-gqsp/9303 "2026-04-16T15:35:31Z")
Hello! I’m using the recent GQSP functionality to implement Hamiltonian simulation of a qubitized operator (cf. Corollary 8 of https://arxiv.org/pdf/2308.01501). To the best of my understanding, the reference constructi… --- ## [Third-party PennyLane plugin for exact and MPS lattice workflows](https://discuss.pennylane.ai/t/third-party-pennylane-plugin-for-exact-and-mps-lattice-workflows/9304)
**Author:** [@gwen](https://discuss.pennylane.ai/u/gwen)\ **Replies:** 1\ **Last updated:** [April 15, 2026, 11:08pm UTC](https://discuss.pennylane.ai/t/third-party-pennylane-plugin-for-exact-and-mps-lattice-workflows/9304 "2026-04-15T23:08:46Z")
I would like to share a third-party PennyLane plugin package that is now working through the standard plugin discovery path, and ask whether there is a recommended process for listing or announcing third-party PennyLane … --- ## [Lightning.qubit with reuploading model](https://discuss.pennylane.ai/t/lightning-qubit-with-reuploading-model/9300)
**Author:** [@Jacob\_Cybulski](https://discuss.pennylane.ai/u/Jacob_Cybulski)\ **Replies:** 4\ **Last updated:** [April 13, 2026, 11:24pm UTC](https://discuss.pennylane.ai/t/lightning-qubit-with-reuploading-model/9300 "2026-04-13T23:24:41Z")
I have a simple reuploading test model, i.e. @qml.qnode(dev, diff\_method='adjoint') # 'adjoint' or 'parameter-shift' def qnn\_model(params, x): for l in range(n\_layers): for q in range(n\_qubits): … --- ## [PF4.4 Differentiate and repear](https://discuss.pennylane.ai/t/pf4-4-differentiate-and-repear/9293)
**Author:** [@simpsoe](https://discuss.pennylane.ai/u/simpsoe)\ **Replies:** 1\ **Last updated:** [March 30, 2026, 8:29pm UTC](https://discuss.pennylane.ai/t/pf4-4-differentiate-and-repear/9293 "2026-03-30T20:29:08Z")
Having trouble with this and got stuck. Any help is appreciated. dev = qml.device("default.qubit", wires = 2) @qml.qnode(dev, diff\_method = "parameter-shift", max\_diff = 2) def circuit\_for\_hessian(params): """ Implemen… --- ## [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… --- ## [Qutrits Simulator Doubts](https://discuss.pennylane.ai/t/qutrits-simulator-doubts/9286)
**Author:** [@MirandaCarou](https://discuss.pennylane.ai/u/MirandaCarou)\ **Replies:** 2\ **Last updated:** [March 19, 2026, 5:57pm UTC](https://discuss.pennylane.ai/t/qutrits-simulator-doubts/9286 "2026-03-19T17:57:51Z")
Hi! I’ve been working for a while with the default.qutrit simulator, and I was wondering if there have been any updates on its development. I have a few questions, as well as some general curiosities. First of all, I h… --- ## [PennyLane Fundamentals / Quantum Operations / ControlledQubitUnitary](https://discuss.pennylane.ai/t/pennylane-fundamentals-quantum-operations-controlledqubitunitary/9283)
**Author:** [@kasterma](https://discuss.pennylane.ai/u/kasterma)\ **Replies:** 1\ **Last updated:** [March 9, 2026, 9:25pm UTC](https://discuss.pennylane.ai/t/pennylane-fundamentals-quantum-operations-controlledqubitunitary/9283 "2026-03-09T21:25:08Z")
On page PennyLane Fundamentals | Quantum Operations | PennyLane Codebook the examples involving the ControlledQubitUnitary are incorrect. According to qml.ControlledQubitUnitary — PennyLane 0.44.0 documentation the inte… --- ## [Codercise V.1.4 - Training a model](https://discuss.pennylane.ai/t/codercise-v-1-4-training-a-model/7495)
**Author:** [@feynmannlu](https://discuss.pennylane.ai/u/feynmannlu)\ **Replies:** 6\ **Last updated:** [March 7, 2026, 7:58am UTC](https://discuss.pennylane.ai/t/codercise-v-1-4-training-a-model/7495 "2026-03-07T07:58:34Z")
I don’t understand what problem. Have someone also encounter the same problem? --- ## [Typos: H3 + I4 + \[min title len bonus\]](https://discuss.pennylane.ai/t/typos-h3-i4-min-title-len-bonus/9282)
**Author:** [@float2](https://discuss.pennylane.ai/u/float2)\ **Replies:** 1\ **Last updated:** [March 6, 2026, 4:04pm UTC](https://discuss.pennylane.ai/t/typos-h3-i4-min-title-len-bonus/9282 "2026-03-06T16:04:32Z")
Hi, I think I found a few typos, please review them. H3 / Theory / The quantum description: “…to replace S\_z it with…" H3 / Theory / Appendix - The Matrix Exponential: “We we need to…” H3 / Codercise H.3.1d: “So, we’… --- ## [Issue with qml.poly\_to\_angles(poly, "GQSP")](https://discuss.pennylane.ai/t/issue-with-qml-poly-to-angles-poly-gqsp/8103)
**Author:** [@HYW](https://discuss.pennylane.ai/u/HYW)\ **Replies:** 17\ **Last updated:** [March 5, 2026, 1:42am UTC](https://discuss.pennylane.ai/t/issue-with-qml-poly-to-angles-poly-gqsp/8103 "2026-03-05T01:42:26Z")
Hi, I have an issue when using qml.poly\_to\_angles(poly, “GQSP”). The code is okay for num = 10 or below but it doesn’t work when num is greater than 10. I need to have num = 30. import pennylane as qml import numpy as… --- ## [Troubles with mapping virtual to physical qubits on a IBM's backend](https://discuss.pennylane.ai/t/troubles-with-mapping-virtual-to-physical-qubits-on-a-ibms-backend/9276)
**Author:** [@Alex1](https://discuss.pennylane.ai/u/Alex1)\ **Replies:** 6\ **Last updated:** [March 4, 2026, 12:56am UTC](https://discuss.pennylane.ai/t/troubles-with-mapping-virtual-to-physical-qubits-on-a-ibms-backend/9276 "2026-03-04T00:56:54Z")
Hi! A simple question that however is causing me some troubles. I’m trying to design a personalized schedule for IBM’s backend (real QPU). All the customized settings but one work. Specifically, I was trying to map the… --- ## [Lightning qubit not converging](https://discuss.pennylane.ai/t/lightning-qubit-not-converging/9271)
**Author:** [@tab1e](https://discuss.pennylane.ai/u/tab1e)\ **Replies:** 8\ **Last updated:** [March 2, 2026, 11:26pm UTC](https://discuss.pennylane.ai/t/lightning-qubit-not-converging/9271 "2026-03-02T23:26:04Z")
I have a variational quantum circuit algorithm. The code is perfectly fine and the algorithm will converge for default.qubit. However, when I left all the code unchanged, just changing the setting from default.qubit to l… --- ## [How to compute fidelity between two squeezed coherent states in Strawberry Fields (bosonic backend)?](https://discuss.pennylane.ai/t/how-to-compute-fidelity-between-two-squeezed-coherent-states-in-strawberry-fields-bosonic-backend/9275)
**Author:** [@Orleans\_Cardoso](https://discuss.pennylane.ai/u/Orleans_Cardoso)\ **Replies:** 3\ **Last updated:** [February 27, 2026, 7:27pm UTC](https://discuss.pennylane.ai/t/how-to-compute-fidelity-between-two-squeezed-coherent-states-in-strawberry-fields-bosonic-backend/9275 "2026-02-27T19:27:11Z")
Hello everyone, I would like to compute the fidelity between two squeezed coherent states using the Strawberry Fields bosonic backend, but I am not sure about the correct method. As far as I understand, a squeezed cohe… --- ## [Speeding up strawberryfields.tf with GPU](https://discuss.pennylane.ai/t/speeding-up-strawberryfields-tf-with-gpu/9272)
**Author:** [@Daniel\_Wang](https://discuss.pennylane.ai/u/Daniel_Wang)\ **Replies:** 3\ **Last updated:** [February 26, 2026, 11:47pm UTC](https://discuss.pennylane.ai/t/speeding-up-strawberryfields-tf-with-gpu/9272 "2026-02-26T23:47:55Z")
Hello, I read the instructions for using different devices for simulating photonic operations. It seems that strawberryfields.tf is the fastest one for simulating large scale problems with support of gradients backprop.… --- ## [A new way of thinking](https://discuss.pennylane.ai/t/a-new-way-of-thinking/9273)
**Author:** [@ronaldo](https://discuss.pennylane.ai/u/ronaldo)\ **Replies:** 1\ **Last updated:** [February 26, 2026, 5:08pm UTC](https://discuss.pennylane.ai/t/a-new-way-of-thinking/9273 "2026-02-26T17:08:45Z")
I’m exploring a toy model where spacetime emerges from the interactions of information‑carrying threads. Each thread represents a line of quantum information, and when two threads cross, that crossing acts like an entang… --- ## [QSVT for odd degree polynomial: mathematical expansion](https://discuss.pennylane.ai/t/qsvt-for-odd-degree-polynomial-mathematical-expansion/9224)
**Author:** [@psansebastian](https://discuss.pennylane.ai/u/psansebastian)\ **Replies:** 2\ **Last updated:** [February 26, 2026, 4:54pm UTC](https://discuss.pennylane.ai/t/qsvt-for-odd-degree-polynomial-mathematical-expansion/9224 "2026-02-26T16:54:59Z")
Hello, In this demo, shouldn’t the mathematical expansion of the odd-degree polynomial contain an additional block-encoded unitary application between the first projector-controlled phase gate and the multiplication ope… --- ## [Hybrid backends: qubits and bosons](https://discuss.pennylane.ai/t/hybrid-backends-qubits-and-bosons/9232)
**Author:** [@Taha](https://discuss.pennylane.ai/u/Taha)\ **Replies:** 3\ **Last updated:** [February 25, 2026, 5:17am UTC](https://discuss.pennylane.ai/t/hybrid-backends-qubits-and-bosons/9232 "2026-02-25T05:17:54Z")
Hi, I hope that you are doing well. I am aware that a similar question has been asked before here: Hybrid qubit-qumode gate . Since the question was asked some years ago, I am checking for potential updates. I was cur… --- ## [Issue with parallelization/broadcasting with Pytorch](https://discuss.pennylane.ai/t/issue-with-parallelization-broadcasting-with-pytorch/9269)
**Author:** [@Taha](https://discuss.pennylane.ai/u/Taha)\ **Replies:** 1\ **Last updated:** [February 25, 2026, 3:24am UTC](https://discuss.pennylane.ai/t/issue-with-parallelization-broadcasting-with-pytorch/9269 "2026-02-25T03:24:23Z")
Dear Pennylane community, I hope that you are doing well. I was trying to run a lightning.qubit circuit with the Pytorch interface. In my circuit, I run the following command: x = torch.vmap(self.q\_circ\_torch)(self.… [Previous page](https://discuss.pennylane.ai/latest.md?page=1) [Next page](https://discuss.pennylane.ai/latest.md?page=3)