experimental · research and evaluation use
Deep circuits, condensed-matter quenches, error-correction experiments: the regimes every simulator fails in are the regimes a researcher most needs a number for. Catalyst‑Q moves the observable instead of the state, and returns every value with an error certificate — 0 when the answer is exact, an unconditional bound when it is not. The cost is the size of the observable, not the number of qubits.
Exact through the light cone. Certified beyond it. The wall is stated on every page, with the measurement that found it — the scope is published.
Observable-side record cq-front-2026-09-01, measured 2026-09-01 against numpy dense statevector (n ≤ 20), qiskit-aer 0.17.2 matrix-product state (n ≥ 24), Majorana-chart Pfaffian (matchgate circuits). Raw record. Width-side record cq-prod-2026-08-22-ed64918e, revision 5a0d43a69f5e. Both on the evidence page.
three surfaces, one meter
Trotterised dynamics, variational ansätze, random brickwork. The observable is transported backwards through the circuit; exact through the light cone at any width, certified past it. Matchgate circuits are detected and computed exactly in the fermionic chart. Every job returns a citable record.
Open the route → 02 · qec labStabiliser simulators cannot represent a coherent rotation and dense ones stop near 25 qubits. The syndrome-resolved logical channel comes from one transform over the stabiliser group — d=3 and d=5 live, d=7 offline — next to threshold curves at any distance.
Open the lab → 03 · verification at widthDid the transpiler preserve this operator? Is the circuit and its inverse the identity? Answered exactly at a million declared qubits in 3.2 seconds, against analytic truth, in CI.
Read the reference →the mechanism
A Pauli observable is pulled backwards through the circuit. Clifford gates permute it with a sign; other gates split it into a small weighted bundle. Nothing of size 2n ever exists.
Terms below a salience threshold are dropped, and every dropped weight is added to a bound: the reported value is within that bound of the exact one, unconditionally. A certificate of 0 is an exact answer.
When a bundle grows, it is usually the representation and not the physics. The TFIM order parameter that cost 6.9M terms in the Pauli chart is a 200-line Pfaffian in the fermionic one — exact at 200 sites in 7.7 s.
Scrambled circuits at depth of order the width fill the Pauli space: 65,535 of 65,536 terms at 8 qubits, depth 14. That is the #P wall on the readout side. It is reported as such, never rounded off.
scope
Stating the boundary next to the result is the point. In a field where every benchmark is self-reported, the vendor that publishes its own limits is the one worth checking.
who this is for
Quench dynamics past the state-vector ceiling, with a number you can put in a paper and a certificate a referee can check.
Coherent-error logical channels that stabiliser tools cannot express; threshold sweeps at any distance in milliseconds per shot.
The observable you were about to pay a QPU to estimate, computed first. One prevented $6,000 run pays for a year.
A correctness oracle in CI above the width your own simulator reaches, and an independent verification record for a claim you are evaluating.
Create an account, open the console, and run your own circuit. The free tier needs no card and carries a 60,000-word bundle budget — enough for a depth-4 random circuit at any width.
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