Constant Rate Codes with Fully Addressable Transversal T: Good Codes, Sparse Checks

Abstract: Recent work by Wills constructed codes with constant rate and transversal $T$. Extending this line of work, we construct asymptotically good CSS codes with \textbf{fully addressable} transversal $T$, permitting selective control over which logical qubits receive a $T$ gate. We also give Pauli-LDPC codes with transversal $T$ and growing distance at vanishing rate; and a protected-subsystem construction with fully addressable transversal $T$, constant protected rate, distance $Ω(\sqrt n)$, and sparse (non-Pauli) checks. More generally, we obtain asymptotically good binary codes with full transversal addressability for every fixed finite-order one-qubit gate, retaining CSS realizations for dyadic phase gates such as $\sqrt T$ and using generally nonadditive codes for rotations such as $R_z(π/7)$. The remaining challenge is to construct asymptotically good Pauli-LDPC codes with fully addressable transversal non-Clifford one-qubit gates.