Interaction order sets the onset cost of steady-state quantum magic

Abstract

Maintaining quantum magic under continuous noise requires coherent control and a supply of purity. We determine the cost of local stabilizer replacement resets sustaining any positive stationary magic in autonomous qubit networks with depolarization rate $γ$, interactions on at most $k$ sites, and Hamiltonian strength $J$ per site. An exact global stabilizer decomposition and a matching finite construction give the optimal onset scaling $γ(γ/J)^{1/(k-1)}$, uniformly over network size and noisy ancillas. For two-body interactions, the leading maximal-reset-rate coefficient is $1/(2\sqrt2)$ for every fixed finite size $N\ge2$, allowing mixed reset targets and heterogeneous rates. The same coefficient holds uniformly over growing networks with pure Pauli targets and equal reset rates. The converse combines hafnian stabilizer geometry with a positive random-order forest expansion.