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This paper aims to construct optimal quaternary additive codes with non-integer dimensions. Firstly, we propose combinatorial constructions of quaternary additive constant-weight codes, alongside additive anticode construction. Subsequently, we propose generalized Construction X, which facilitates the construction of non-integer dimensional optimal additive codes from linear codes. Then, we construct ten classes of optimal quaternary non-integer dimensional additive codes through these two methods. As an application, we also determine the optimal additive $[n,3.5,n-t]_4$ codes for all $t$ with variable $n$, except for $t=6,7,12$., Comment: This work was mainly completed in the summer of 2023, and here we add some new developments. Everyone is welcome to discuss issues related to additional code with the first author

In this paper, we obtain sufficient and necessary conditions for quasi-cyclic codes with index even to be symplectic self-orthogonal. Then, we propose a method for constructing symplectic self-orthogonal quasi-cyclic codes, which allows arbitrary polynomials that coprime $x^{n}-1$ to construct symplectic self-orthogonal codes. Moreover, by decomposing the space of quasi-cyclic codes, we provide lower and upper bounds on the minimum symplectic distances of a class of 1-generator quasi-cyclic codes and their symplectic dual codes. Finally, we construct many binary symplectic self-orthogonal codes with excellent parameters, corresponding to 117 record-breaking quantum codes, improving Grassl's table (Bounds on the Minimum Distance of Quantum Codes. http://www.codetables.de).

Construction of quantum codes and entanglement-assisted quantum codes with good parameters via classical codes is an important task for quantum computing and quantum information. In this paper, by a family of one-generator quasi-cyclic codes, we provide quasi-cyclic extended constructions that preserve the self-orthogonality to obtain stabilizer quantum codes. As for the computational results, some binary and ternary stabilizer codes with good parameters are constructed. Moreover, we present methods to construct maximal-entanglement entanglement-assisted quantum codes by means of the class of quasi-cyclic codes and their extended codes. As an application, some good maximal-entanglement entanglement-assisted quantum codes are obtained and their parameters are compared.

Conjucyclic codes are an important and special family of classical error-correcting codes, which have been used to construct binary quantum error-correcting codes (QECCs). However, at present, the research on the conjucyclic codes is extremely insufficient. This paper will explore the algebraic structure of additive conjucyclic codes over $\mathbb{F}_{q^{2}}$ for the first time. Mainly via the trace function from $\mathbb{F}_{q^{2}}$ down $\mathbb{F}_{q}$, we will firstly build an isomorphic mapping between $q^2$-ary additive conjucyclic codes and $q$-ary linear cyclic codes. Since the mapping preserves the weight and orthogonality, then the dual structure of these codes with respect to the alternating inner product will be described. Then a new construction of QECCs from conjucyclic codes can be obtained. Finally, the enumeration of $q^2$-ary additive conjucyclic codes of length $n$ and the explicit forms of their generator and parity-check matrices will be determined.

In this work, our main objective is to construct quantum codes from quasi-twisted (QT) codes. At first, a necessary and sufficient condition for Hermitian self-orthogonality of QT codes is introduced by virtue of the Chinese Remainder Theorem (CRT). Then we utilize these self-orthogonal QT codes to provide quantum codes via the famous Hermitian Construction. Moreover, we present a new construction method of q-ary quantum codes, which can be viewed as an effective generalization of the Hermitian Construction. General QT codes that are not self-orthogonal are also employed to construct quantum codes. As the computational results, some binary, ternary and quaternary quantum codes are constructed and their parameters are determined, which all exceed the Quantum Gilbert-Varshamov (GV) Bound. In the binary case, a small number of quantum codes are derived with strictly improved parameters compared with the current records. In the ternary and quaternary cases, our codes fill some gaps or have better performances than the current results., Comment: We want to perfect this paper