Entropic proofs of Singleton bounds for quantum error-correcting codes

Markus Grassl, Felix Huber, Andreas Winter

Published 2020-10-15Version 1

We show that a relatively simple reasoning using von Neumann entropy inequalities yields a robust proof of the quantum Singleton bound for quantum error-correcting codes (QECC). For entanglement-assisted quantum error-correcting codes (EAQECC) and catalytic codes (CQECC), the generalised quantum Singleton bound was believed to hold for many years until recently one of us found a counterexample [MG, arXiv:2007.01249]. Here, we rectify this state of affairs by proving the correct generalised quantum Singleton bound for CQECC, extending the above-mentioned proof method for QECC; we also prove information-theoretically tight bounds on the entanglement-communication tradeoff for EAQECC. All of the bounds relate block length $n$ and code length k for given minimum distance d and we show that they are robust, in the sense that they hold with small perturbations for codes which only correct most of the erasure errors of less than d letters. In contrast to the classical case, the bounds take on qualitatively different forms depending on whether the minimum distance is smaller or larger than half the block length.