Construction of the mutually orthogonal extraordinary supersquares

TL;DR

This paper introduces and constructs mutually orthogonal supersquares, especially extraordinary ones, of order 4, which are relevant for quantum information, extending the classical Latin squares concept.

Contribution

It defines supersquares via generating subgroups, presents a construction method, and classifies the most general sets of orthogonal extraordinary supersquares of order 4.

Findings

Complete sets of mutually orthogonal extraordinary supersquares of order 4 identified

Type I and Type II classifications established

Special case of Latin squares as Type I included

Abstract

Our purpose is to determine the complete set of mutually orthogonal squares of order $d$, which are not necessary Latin. In this article, we introduce the concept of supersquare of order $d$, which is defined with the help of its generating subgroup in $\mathbb{F}_d\times \mathbb{F}_d$. We present a method of construction of the mutually orthogonal supersquares. Further, we investigate the orthogonality of extraordinary supersquares, a special family of squares, whose generating subgroups are extraordinary. The extraordinary subgroups in $\mathbb{F}_d\times \mathbb{F}_d$ are of great importance in the field of quantum information processing, especially for the study of mutually unbiased bases. We determine the most general complete sets of mutually orthogonal extraordinary supersquares of order 4, which consist in the so-called Type I and Type II. The well-known case of $d-1$ mutually orthogonal Latin squares is only a special case, namely Type I.