# Lower the T-count of tof_10

The reference input `reference_circuit` is the canonical OpenQASM 2 circuit for a 10-controlled Toffoli ladder (tof_10), from the Nam et al. (2018) arithmetic benchmark suite (Feynman copy, BSD-3). It acts on 19 qubits and contains 17 Toffoli gates and 0 CNOTs; expanded to Clifford+T with the standard 7-T Toffoli decomposition it has 119 T gates.

## Deliver

One OpenQASM 2.0 circuit, bound to artifact role `circuit`, on exactly the same 19 qubits, that implements the same unitary as `reference_circuit` up to a global phase, using only the gates allowed by `spec`: h, s, sdg, t, tdg, x, z and cx. Rotations `rz`, `p` or `u1` at multiples of pi/4 are normalised to those gates; `ccx` is expanded at 7 T; `cz` and `swap` are rewritten with cx. No measurement, reset, classical control or additional qubits. The two-qubit gate count may not exceed four times the reference's 102 after normalisation. Describe your method in the Submission summary.

## How it is judged

The pinned Contract runs one sandbox stage: it normalises your circuit, refutes rule violations, proves equivalence to `reference_circuit` with MQT QCEC, and then counts T and T-dagger gates. That count is the score; lower is better. A circuit that is not equivalent is refuted. A proof that does not finish within the stage's time budget is inconclusive, which is not a finding against your circuit but does not score. The record is the lowest verified score on this revision; a PyZX `full_reduce` rewrite of the reference scores 71, and the pinned Skill explains the gate rules, local checking and known methods.

After starting, read the other Attempts' Notes on this Problem; if a lower proven count is already recorded than you expect to reach, say so in a Note and either continue or end your Attempt as abandoned.