We present a family of non-additive quantum codes based on Goethals and Preparata codes with parameters ((2m, 22m-5m+1, 8)). The dimension of these codes is eight times higher than the dimension of the best known additive quantum codes of equal length and minimum distance.
Introduction Most quantum error-correcting codes (QECCs) that are designed to correct local errors are stabilizer codes that correspond to additive classical codes. Because of this correspondence, stabilizer codes are also referred to as additive codes, while nonstabilizer codes are called nonadditive codes. Shortly after the invention of stabilizer codes by Gottesman [G96a] and independently Calderbank et al. [CRS+98], the nonadditive ((5, 6, 2)) code was found [RHS+97], which constitutes the first example of a nonadditive quantum code with a higher dimension than any stabilizer code of equal length and minimum distance. About ten years later, the first one-error-correcting ((9, 12, 3)) code and the optimal ((10, 24, 3)) code were found [YCL+09, YCO07], both better than any stabilizer code of the same length. Here we describe a framework that not only allows a joint description of these codes, but also enables the construction of new nonadditive codes with better parameters than the best known stabilizer codes. These codes are based on the classical nonlinear Goethals and Preparata codes, which themselves are better than any classical linear code. In Section 10.3, the framework will be presented from two different points of view, namely union stabilizer codes and codeword stabilized codes, each highlighting different aspects of the construction. To illustrate the relationship of these nonadditive codes to stabilizer codes we first recall the main aspects of the latter. Section 10.4 is devoted to methods for obtaining new codes, including the aforementioned quantum Goethals–Preparata codes.
Quantum MDS Codes with length n≡0,1(mod2q±1)
An important family of quantum codes is the quantum maximum-distance-separable (MDS) codes. In this paper, we construct some new classes of quantum MDS codes by generalized Reed-Solomon (GRS) codes and Hermitian construction. In addition, the length n of most of the quantum MDS codes we constructed satisfies n≡0,1(mod2q±1), which is different from previously known code lengths. At the same time, the quantum MDS codes we construct have large minimum distances that are greater than q/2+1.
It is an important task to construct quantum maximum-distance-separable (MDS) codes with good parameters. In the present paper, we provide six new classes ofq-ary quantum MDS codes by using generalized Reed–Solomon (GRS) codes and Hermitian construction. The minimum distances of our quantum MDS codes can be larger than2q+1. Three of these six classes of quantum MDS codes have longer lengths than the ones constructed in[1]and[2], hence some of their results can be easily derived from ours via the propagation rule. Moreover, some known quantum MDS codes of specific lengths can be seen as special cases of ours and the minimum distances of some known quantum MDS codes are also improved as well.
Many families of binary nonlinear codes (e.g., Kerdock, Goethals, Delsarte–Goethals, Preparata) can be very simply constructed from linear codes over the Z4 ring (ring of integers modulo 4), by applying the Gray map to the quaternary symbols. Generalized Kerdock codes represent an extension of classical Kerdock codes to the Z2S ring. In this paper, we develop two novel soft-input decoders, designed to exploit the unique structure of these codes. We introduce a novel soft-input ML decoding algorithm and a soft-input soft-output MAP decoding algorithm of generalized Kerdock codes, with a complexity of O(NSlog2N), where N is the length of the Z2S code, that is, the number of Z2S symbols in a codeword. Simulations show that our novel decoders outperform the classical lifting decoder in terms of error rate by some 5 dB.
In this paper, we construct families of nonbinary quantum codes from classical negacyclic codes. The BCH bound for negacyclic codes is applied to determine the dimension and distance of these quantum codes. The parameters of these quantum codes are good compared with the ones available in the literature. We also construct a family of quantum maximum-distance-separable codes with parameters ${[[q+1,q\ensuremath{-}2d+3,d]]}_{q}$, where $q\ensuremath{\equiv}1\phantom{\rule{0.28em}{0ex}}\mathrm{mod}\phantom{\rule{0.28em}{0ex}}4$ and $2\ensuremath{\le}d\ensuremath{\le}(q+3)/2$.