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Bowtie VarQTE: A Resource-Efficient Quantum State Preparation Primitive

arXiv Quantum Physics
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⚡ Quantum Brief
Researchers from IBM and Italian institutions introduced a hybrid quantum-classical framework called bowtie VarQTE to optimize quantum state preparation by minimizing quantum resource demands. The method leverages causal light-cones to offload calculations to classical simulations where possible, reducing quantum circuit requirements while maintaining exact parameter updates via McLachlan’s variational principle for improved stability. Unlike tensor-network-based approaches like AQC—which require classical approximations of target states—bowtie VarQTE achieves comparable fidelity without this bottleneck, as demonstrated in numerical experiments. Tests on 2D systems show it reduces quantum resource needs compared to standard Krylov diagonalization, enabling efficient real and imaginary time evolution for sample-based algorithms. The work positions VarQTE as a promising primitive for preparing structured quantum states, balancing resource efficiency with accuracy in near-term quantum computing applications.
Bowtie VarQTE: A Resource-Efficient Quantum State Preparation Primitive

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Quantum Physics arXiv:2605.20331 (quant-ph) [Submitted on 19 May 2026] Title:Bowtie VarQTE: A Resource-Efficient Quantum State Preparation Primitive Authors:Marc Drudis, Alberto Baiardi, Mattia Chiurco, Francesco Tacchino, Stefan Woerner, Christa Zoufal View a PDF of the paper titled Bowtie VarQTE: A Resource-Efficient Quantum State Preparation Primitive, by Marc Drudis and 5 other authors View PDF Abstract:The preparation of quantum states is a fundamental requirement for many quantum algorithms. A native route to preparing physically structured states is based on short-time simulation of dynamical processes, such as real or imaginary time evolution. This work presents a resource-efficient framework for the approximation thereof with \textit{bowtie \ac{VarQTE}} which uses classical simulation where possible and quantum resources where necessary. We introduce a framework that leverages existing causal light-cones to minimize quantum resource requirements in the evaluation of gradient and quantum geometric tensor terms by utilizing classical simulation methods for causally relevant subcircuits. This in turn enables exact parameter updates according to McLachlan's variational principle and, thereby, improves numerical stability. We conduct a comparison with a state preparation method that is based on a tensor-network compiled Trotter algorithm: approximate quantum compilation (AQC). In recent work, this approach has shown impressive performance. However, its key-bottleneck is the necessity to have a classical (approximate) representation of the target state. Our numerical experiments indicate that bowtie VarQTE can achieve comparable fidelities without this requirement. We further illustrate how bowtie VarQTE can facilitate a state-preparation pipeline that combines the simulation of imaginary and real time evolution for a sample-based quantum algorithm. In fact, results on 2D systems show how bowtie VarQTE can reduce the quantum requirements compared to standard, sample-based Krylov diagonalization calculations. Our results indicate that VarQTE is a promising primitive for the preparation of physically structured quantum states that reduces requirements on quantum resources by leveraging existing structures and the associated possibility of enabling classical simulations. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2605.20331 [quant-ph] (or arXiv:2605.20331v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2605.20331 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Marc Drudis [view email] [v1] Tue, 19 May 2026 18:00:03 UTC (1,148 KB) Full-text links: Access Paper: View a PDF of the paper titled Bowtie VarQTE: A Resource-Efficient Quantum State Preparation Primitive, by Marc Drudis and 5 other authorsView PDFTeX Source view license Current browse context: quant-ph new | recent | 2026-05 References & Citations INSPIRE HEP NASA ADSGoogle Scholar Semantic Scholar export BibTeX citation Loading... BibTeX formatted citation × loading... Data provided by: Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Code, Data and Media Associated with this Article alphaXiv Toggle alphaXiv (What is alphaXiv?) Links to Code Toggle CatalyzeX Code Finder for Papers (What is CatalyzeX?) DagsHub Toggle DagsHub (What is DagsHub?) GotitPub Toggle Gotit.pub (What is GotitPub?) Huggingface Toggle Hugging Face (What is Huggingface?) ScienceCast Toggle ScienceCast (What is ScienceCast?) Demos Demos Replicate Toggle Replicate (What is Replicate?) Spaces Toggle Hugging Face Spaces (What is Spaces?) Spaces Toggle TXYZ.AI (What is TXYZ.AI?) Related Papers Recommenders and Search Tools Link to Influence Flower Influence Flower (What are Influence Flowers?) Core recommender toggle CORE Recommender (What is CORE?) Author Venue Institution Topic About arXivLabs arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them. Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs. Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)

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Source: arXiv Quantum Physics