Fault-tolerant quantum computing will require circuits that are hard to simulate classically: QEC codes, magic-state distillation, and cultivation protocols that mix thousands of Clifford operations with the non-Clifford gates that make them useful. Today the Bloqade team released Tsim 1.0.0, and these circuits are now within reach for researchers and developers preparing for the fault-tolerant era. A 463-qubit end-to-end magic-state cultivation circuit, for example, compresses into a statevector on just six active qubits. Against the previous release, sampling on cultivation and distillation benchmarks runs thousands to hundreds of thousands of times faster, and compilation that once took seconds now takes milliseconds, all on a single workstation. QuEra’s own QEC teams rely on exactly this kind of simulation to design and verify the protocols behind our roadmap, and now anyone can run them at the same pace.

The gains come from a new approach, not more backend compute. Tsim first simplifies a circuit as a ZX diagram, stripping away Clifford structure and isolating the small logical core that actually needs quantum simulation. That core is then run on a new active statevector backend, which builds on key insights from the open-source Clifft and SymFT projects, with shots that share equivalent noise sharing a single statevector. The ZX engine itself has been rewritten in Rust. In head-to-head benchmarks, Tsim reaches the lowest active width of the three simulators on every circuit tested, and since simulation cost grows exponentially with that width, lower width translates directly into faster sampling. We are also working to contribute Tsim’s ZX compiler pass back to Clifft so the wider community benefits.

Tsim is part of a larger Bloqade strategy. It is the fast, exact sampler for noisy near-Clifford QEC gadgets. PPVM, the Pauli Propagation Virtual Machine we released earlier this year, is the system-level emulator that can account for the limitations of Tsim: neutral-atom noise including atom loss and leakage, classical control flow running alongside quantum operations, and real-time decoding. Together they mean QuEra now spans the simulation spectrum for fault-tolerant quantum computing, from verifying a single distillation gadget to emulating how a Libra-class machine with more than 10,000 physical qubits will behave as a complete system.

Both tools are open source in Bloqade. Read the full Tsim 1.0.0 technical post or start building circuits with feedforward and real-time decoding in QEC Studio.

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