Rather Suhail Ahmad, Aravinda S, Lakshminarayan Arul
Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India.
Phys Rev Lett. 2020 Aug 14;125(7):070501. doi: 10.1103/PhysRevLett.125.070501.
Maximally entangled bipartite unitary operators or gates find various applications from quantum information to many-body physics wherein they are building blocks of minimal models of quantum chaos. In the latter case, they are referred to as "dual unitaries." Dual unitary operators that can create the maximum average entanglement when acting on product states have to satisfy additional constraints. These have been called "2-unitaries" and are examples of perfect tensors that can be used to construct absolutely maximally entangled states of four parties. Hitherto, no systematic method exists in any local dimension, which results in the formation of such special classes of unitary operators. We outline an iterative protocol, a nonlinear map on the space of unitary operators, that creates ensembles whose members are arbitrarily close to being dual unitaries. For qutrits and ququads we find that a slightly modified protocol yields a plethora of 2-unitaries.
最大纠缠二分酉算子或门在从量子信息到多体物理等诸多领域有着广泛应用，在多体物理中它们是量子混沌最小模型的构建要素。在后一种情况下，它们被称为“对偶酉算子”。作用于积态时能产生最大平均纠缠的对偶酉算子必须满足额外的约束条件。这些被称为“2 - 酉算子”，是可用于构建四方绝对最大纠缠态的完美张量的示例。迄今为止，在任何局部维度中都不存在形成此类特殊酉算子类别的系统方法。我们概述了一种迭代协议，即酉算子空间上的非线性映射，它能创建其成员任意接近对偶酉算子的系综。对于三量子比特和四量子比特，我们发现稍微修改后的协议能产生大量的2 - 酉算子。
