量子系统C<sup><italic>d</italic></sup>⊗C<sup><italic>kd</italic></sup>中无偏的最大纠缠基的构造
摘要
In this paper, we study the concrete construction of mutually unbiased maximally entangled bases in bipartite systems C<sup><italic>d</italic></sup> ⊗C<sup><italic>kd</italic></sup> (<italic>k</italic> ∈ <italic>Z</italic><sup>+</sup>). We first analyze and simplify the sufficient and necessary conditions of two maximally entangled bases to be mutually unbiased in C<sup><italic>d</italic></sup> ⊗C<sup><italic>kd</italic></sup>, then we use matrix forms to illustrate these conditions in C<sup>2</sup> ⊗C<sup>2k</sup> and C<sup>3</sup> ⊗C<sup>3k</sup> and generalize them in C<sup><italic>d</italic></sup> ⊗C<sup><italic>kd</italic></sup>. Thus we find that the sufficient and necessary conditions of two maximally entangled bases to be mutually unbiased in C<sup><italic>d</italic></sup> ⊗C<sup><italic>kd</italic></sup> are translating to the conditions of transit matrices <italic>T</italic><sub><italic>kd</italic></sub> between two orthonormal bases in C<sup><italic>kd</italic></sup> satisfy, that is, <italic>T</italic><sub><italic>kd</italic></sub> can be divided into <italic>k</italic><sup>2</sup> submatrices of <italic>d</italic> ×<italic>d</italic> satisfying same equations. So the problem of constructing mutually unbiased maximally entangle bases in C<sup><italic>d</italic></sup> ⊗C<sup><italic>kd</italic></sup> (<italic>k</italic> ∈ <italic>Z</italic><sup>+</sup>) are changing to the choice of transit matrices in Ckd. According the above equations of transit matrices in Ckd, we first construct two transit matrices in C<sup>2</sup>, C<sup>3</sup> and C<sup>4</sup>, then we find that using any unitary matrix with nonzero entities in C<sup><italic>k</italic></sup> to tensor product the above chosen transit matrices in C<sup><italic>d</italic></sup>(<italic>d</italic>= 2;3;4) from left, we can easily get the transit matrices in C<sup><italic>kd</italic></sup>. Hence the choice of transit matrices in C<sup><italic>kd</italic></sup> is changing to the choice of unitary ma