Asymmetric Quantum Concatenated and Tensor Product Codes with Large Z-Distances

In many quantum channels, dephasing errors occur more frequently than the amplitude errors - a phenomenon that has been exploited for performance gains and other benefits through asymmetric quantum codes (AQCs). In this paper, we present a new construction of AQCs by combining classical concatenated codes (CCs) with tensor product codes (TPCs), called asymmetric quantum concatenated and tensor product codes (AQCTPCs) which have the following three advantages. First, only the outer codes in AQCTPCs need to satisfy the orthogonal constraint in quantum codes, and any classical linear code can be used for the inner, which makes AQCTPCs very easy to construct. Second, most AQCTPCs are highly degenerate, which means they can correct many more errors than their classical TPC counterparts. Consequently, we construct several families of AQCs with better parameters than known results in the literature. Especially, we derive a first family of binary AQCs with the Z-distance larger than half the block length. Third, AQCTPCs can be efficiently decoded although they