Universal quantum coding

Abstract

Entanglement distillation from noisy bipartite states and reliable quantum communication over noisy channels are fundamental tasks in quantum information theory, yet optimal coding schemes typically rely on prior knowledge of the underlying state or channel. Here, through Schur-Weyl duality, we establish a universal quantum error-correction principle that removes this dependence entirely. We show that the irreducible permutation spaces arising from the local Schur-Weyl decomposition of many identical copies of an unknown bipartite mixed state form maximally entangled quantum code spaces, with an error structure determined entirely by representation theory. Correcting these symmetry-resolved errors yields universal protocols for entanglement distillation and quantum communication that achieve coherent-information rates with exponentially vanishing error and optimal second-order correction. The protocols are invariant under local unitaries and allow both input marginals to be recovered exactly. At finite block length, their achievable rates are governed by an associated Schur-Weyl information spectrum, which we relate to Petz-Rényi conditional entropies of the underlying state. The resulting sample complexity depends only on the relevant spectral ranks, rather than on the respective Hilbert space dimensions. In particular, for $n$-qubit states of $O(\operatorname{poly} n)$ global rank, we show that a Petz-Rényi conditional-entropy promise suffices for optimal sample-efficient entanglement distillation. Altogether, these results identify Schur-Weyl duality as a fundamental and general mechanism for optimal, tomography-free universal quantum coding, placing entanglement distillation, quantum error correction and quantum communication within a unified representation-theoretic framework.