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Stabilizer rank bounds for magic-state orbits

Farrokh Labib, Vincent Russo

quant-ph May 27, 2026 · v1
Accompanies stabrank library with Lean 4 formalizations of all stabilizer-rank decompositions.
Distinct Clifford orbits of magic states can exhibit different stabilizer ranks at small tensor powers. We establish this for qutrits, where the single-qutrit Clifford group has four inequivalent orbits of magic states: Strange, Norrell, Hadamard-eigenstate, and the qutrit T-state, but a nontrivial upper bound on the asymptotic exponent had been pinned down for only the qutrit T-state. For the other three orbits we give explicit stabilizer decompositions, yielding upper bounds on the per-copy asymptotic stabilizer-rank exponent: $γ_S \le \log_3(2)/2 \approx 0.316$ for the Strange state, and $γ_{H_3}, γ_N \le \log_3(4)/3 \approx 0.421$ for the Hadamard-eigenstate and Norrell orbits, all strictly below the prior $γ_{T_3} \le 1/2$ baseline. We also prove the first nontrivial $Ω(m / \log m)$ asymptotic lower bounds for the Hadamard-eigenstate and Norrell orbits, and exhibit two-qutrit Clifford circuits that convert two copies of these states into an injectable phase state with constant success probability, enabling constant-overhead injection of one non-Clifford diagonal gate per orbit. In the case of qubits, we give a closed-form decomposition of the qubit T-type orbit at four copies matching the existing $γ_T \le \log_2(3)/4 \approx 0.396$ exponent via a direct algebraic identity rather than an entangled cat-state construction. An open-source library stabrank accompanies the paper, with Lean 4 proof formalizations of all the decompositions.

For qutrit magic states, the single-qutrit Clifford group has four inequivalent orbits (Strange, Norrell, Hadamard-eigenstate, T-state), but nontrivial stabilizer-rank exponent bounds existed only for the T-state orbit, leaving open whether the orbits have different simulation costs.

Explicit stabilizer decompositions at small tensor powers are constructed for the three non-T-state qutrit orbits, yielding upper bounds on the per-copy asymptotic stabilizer-rank exponent. Lower bounds are established via a qutrit adaptation of subset-sum obstruction techniques. Two-qutrit Clifford conversion circuits are exhibited for the Hadamard-eigenstate and Norrell orbits. All decompositions are machine-checked in Lean 4, and an open-source Python/C++ library (stabrank) accompanies the paper.

Upper bounds: gamma_S <= log_3(2)/2 ~ 0.316 for the Strange state, gamma_{H3}, gamma_N <= log_3(4)/3 ~ 0.421 for Hadamard-eigenstate and Norrell orbits, all strictly below the prior gamma_{T3} <= 1/2. First nontrivial Omega(m/log m) lower bounds are proved for H3 and Norrell orbits. A closed-form qubit T-type decomposition at four copies matches the existing gamma_T <= log_2(3)/4 ~ 0.396 exponent.