{"slug": "clifft-six-months-in", "title": "Clifft, six months in", "summary": "Six months after its launch, the Unitary Foundation's Clifft quantum-circuit simulator has passed 35,000 PyPI downloads and its paper has been cited 18 times, the foundation reported. Across 12 releases, Clifft added symbolic planning, CPU batching, better operation ordering and new compiler optimization passes, producing a 13.6× median sampling speedup over Clifft v0.1.0 across six benchmark workloads, plus leakage and loss noise models and experimental HIP and CUDA GPU backends with HIP contributions from AMD's Jose Manuel Monsalve Diaz. The foundation said AI coding agents handle implementation, review, analysis and documentation of the tool with human guidance, and that agents let a small research team integrate outside advances such as SymFT.", "body_md": "Six months ago, we [introduced Clifft](https://unitary.foundation/posts/2026_clifft/) to make exact simulation of early fault-tolerant protocols feasible. The underlying circuits combine large Clifford backbones with non-Clifford operations that Stim cannot simulate directly, at scales where conventional state-vector simulation becomes impractical. Both software and the underlying theory in this space have moved quickly.\n\nSince launch, Clifft has recorded **more than 35,000 [PyPI downloads](https://pepy.tech/projects/clifft?timeRange=threeMonths&category=version&includeCIDownloads=true&granularity=weekly&viewType=line&versions=Total%2C0.*)**, and its [paper](https://arxiv.org/abs/2604.27058) has been cited **[18 times](https://inspirehep.net/literature/3150655)**.\n\nClifft itself has become faster, gained richer noise models, and added new execution modes. Alongside that technical progress, we have been developing a way of working: using AI agents to continually integrate advances across the field into a dependable research tool.\n\nThe central idea behind Clifft is to avoid paying dense state-vector costs for qubits that don't actively need amplitude tracking. Over the 12 releases since launch, we’ve further reduced remaining overhead through symbolic planning, CPU batching, and better operation ordering. The compiler stage also adds new optimization passes that shrink the active quantum state, eliminating some work altogether. Across a set of six benchmark workloads, we see a **13.6× median sampling speedup over Clifft v0.1.0**.\n\n*See [benchmark methodology](https://unitaryfoundation.github.io/clifft/stable/guide/performance/) for execution settings and measurement details.*\n\nClifft also has experimental [HIP](https://unitaryfoundation.github.io/clifft/stable/development/hip-backend/) and [CUDA](https://unitaryfoundation.github.io/clifft/stable/development/cuda-backend/) GPU backends, with HIP contributions from [Jose Manuel Monsalve Diaz](https://github.com/josemonsalve2) at [AMD](https://www.amd.com/). GPUs offer substantial compute and memory bandwidth, but Clifft’s active state vector can grow and shrink dynamically within a single circuit. When the active state is tiny, processing many shots independently in parallel is a natural fit. As it grows, GPU threads can cooperate on states held in fast shared memory; when it gets very large, execution shifts to parallel updates in global device memory. Learning how best to adapt GPU execution as a circuit moves between these regimes is part of the work ahead.\n\nTo bring simulations closer to real hardware, Clifft now models [leakage and loss noise](https://unitaryfoundation.github.io/clifft/stable/guide/leakage-and-loss/), including state-dependent transitions and their back-action on the remaining quantum state. This makes it possible to study how hardware-specific effects, such as atom loss in neutral-atom architectures, impact fault-tolerant strategies. Recent additions allow leaked or lost qubits to disturb their gate partners and let circuits incorporate leakage and loss checks directly into detectors and feedback. Importantly, these features compose seamlessly with the core near-Clifford simulator, giving you the best of both capabilities in a single tool.\n\nCheck out the [Clifft development blog](https://unitaryfoundation.github.io/clifft/stable/updates/) for more detail on recent releases and their features.\n\nAI played a big role in developing Clifft, and that role continues to grow. Coding agents handle implementation, review, analysis, and documentation, with human guidance and review. Agents expand the range of ideas a small research team can investigate and turn into working software.\n\nAI also lets us rapidly integrate others' innovations. One example is [SymFT](https://arxiv.org/abs/2607.28600), developed by Wang Fang (University of Edinburgh), Huazhe Lou (Arclight Quantum Computing), and Riling Li (Chinese Academy of Sciences). It combined ideas from their earlier SOFT simulator with Clifft's dense active-state representation, then introduced symbolic planning and direct operations on that state for even more speedup. Thanks to AI, Clifft [adopted those developments](https://unitaryfoundation.github.io/clifft/stable/updates/symbolic-sampling/) in August, just a few weeks after the preprint appeared.\n\nA similar exchange with [Tsim](https://github.com/QuEraComputing/tsim), developed by Rafael Haenel, Xiuzhe Luo, and Chen Zhao at QuEra Computing, now runs both ways. Early on, Tsim helped shape Clifft's Stim-compatible interface and workflow. In October, Tsim [merged an active-statevector sampler inspired by Clifft](https://github.com/QuEraComputing/tsim/pull/203) that reads computations directly from simplified ZX diagrams, finding smaller active states and outperforming Clifft on several benchmarks. Completing the loop, Rafael has since [proposed](https://github.com/unitaryfoundation/clifft/pull/606) porting those improvements back to Clifft.\n\nOther times, external work inspires new compiler passes rather than direct ports. For example, [Merlin](https://arxiv.org/abs/2610.06811), developed by Șerban Cercelescu and Mark Koch at Oxford and Arthur Pesah at Freie Universität Berlin, uses a phase-polynomial representation to simulate a broad class of non-Clifford error-correction circuits efficiently. That perspective inspired Clifft to [expand its compiler optimizations](https://github.com/unitaryfoundation/clifft/pull/552) to code-switching circuits with measurements and feedback.\n\nClifft can integrate these advances quickly because its modular compiler design isolates new passes, while extensive testing and validation frameworks give coding agents safe guardrails to iterate fast. Our agents also regularly survey the ecosystem for new techniques to bring in—and just as importantly, we document the [source of these developments](https://unitaryfoundation.github.io/clifft/stable/acknowledgments/) so that credit travels with the ideas.\n\nDifferent simulators bring different strengths, and we encourage researchers to explore them and compare results. With Clifft, we want researchers to benefit from simulation advances without continually redesigning their workflows. Improving that experience is as central to the project as developing new algorithms.\n\nThat means being able to revise a protocol, change a noise model, or add measurements and feedback while continuing to work through a familiar interface. Researchers should be able to concentrate on the experiment they are designing: describing the circuit, choosing physical assumptions, and interpreting the results. Our goal is for Clifft to handle simulation strategy under the hood, so backend improvements automatically translate into faster, more capable experiments.\n\nWhen we launched Clifft, magic-state cultivation was a primary motivation. We wanted to simulate the actual non-Clifford dynamics and test assumptions made using a simpler Clifford proxy. It has been encouraging to see independent work deepen that understanding. [Wan and Zapirain](https://arxiv.org/abs/2609.18922) recovered Clifft’s and SOFT’s numerical estimates through an exact calculation, while [Chan and colleagues](https://arxiv.org/abs/2609.17706) identified a weakness in the original cultivation circuit that the proxy missed. Together, these results show why making exact simulation accessible matters.\n\nIn September, we also presented Clifft at the [Advanced Simulations of Quantum Computations Workshop](https://sites.google.com/view/asqcworkshop/home), the [Quantum Software 2.6 Workshop](https://sites.google.com/view/quantum-software-workshop-2026) and the [International Workshop on Quantum Compilers](https://quantum-compilers.github.io/iwqc2026/) during IEEE Quantum Week. Community contributions have also expanded the project, including the [Qiskit adapter](https://github.com/unitaryfoundation/clifft-qiskit) developed by [Ashmit Gupta](https://github.com/ashmitjsg) during [unitaryHACK](https://unitaryhack.dev/).\n\nWe want Clifft to be shaped by the researchers who use it and the people who help build it. Bring us circuits, difficult noise models, and benchmark cases—or contribute algorithms, code, documentation, and ideas. The exchanges above show how much progress comes from building on one another's work, and we welcome more people into that process. Start with the [documentation](https://unitaryfoundation.github.io/clifft/stable/), try the [playground](https://unitaryfoundation.github.io/clifft/playground/), or join us on [GitHub](https://github.com/unitaryfoundation/clifft) and the [Unitary Foundation Discord](https://discord.unitary.foundation).\n\n<small>This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research, Accelerated Research in Quantum Computing under Award Number DE-SC0025336. This material is also based upon work supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Science Center.</small>", "url": "https://wpnews.pro/news/clifft-six-months-in", "canonical_source": "https://unitary.foundation/posts/2026_clifft_six_months/", "published_at": "2026-10-30 00:00:00+00:00", "updated_at": "2026-10-30 14:19:03.576860+00:00", "lang": "en", "topics": ["artificial-intelligence", "ai-agents", "ai-research", "developer-tools"], "entities": ["Clifft", "Unitary Foundation", "Stim", "AMD", "Jose Manuel Monsalve Diaz", "SymFT", "Wang Fang", "Huazhe Lou"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/clifft-six-months-in", "markdown": "https://wpnews.pro/news/clifft-six-months-in.md", "text": "https://wpnews.pro/news/clifft-six-months-in.txt", "jsonld": "https://wpnews.pro/news/clifft-six-months-in.jsonld"}}