Foligno Alessandro, Kos Pavel, Bertini Bruno
School of Physics and Astronomy, <a href="https://ror.org/01ee9ar58">University of Nottingham</a>, Nottingham, NG7 2RD, United Kingdom.
Centre for the Mathematics and Theoretical Physics of Quantum Non-Equilibrium Systems, <a href="https://ror.org/01ee9ar58">University of Nottingham</a>, Nottingham, NG7 2RD, United Kingdom.
Phys Rev Lett. 2024 Jun 21;132(25):250402. doi: 10.1103/PhysRevLett.132.250402.
We study the spreading of quantum information in a recently introduced family of brickwork quantum circuits that generalizes the dual-unitary class. These circuits are unitary in time, while their spatial dynamics is unitary only in a restricted subspace. First, we show that local operators spread at the speed of light as in dual-unitary circuits, i.e., the butterfly velocity takes the maximal value allowed by the geometry of the circuit. Then, we prove that the entanglement spreading can still be characterized exactly for a family of compatible initial states (in fact, for an extension of the compatible family of dual-unitary circuits) and that the asymptotic entanglement slope is again independent on the Rényi index. Remarkably, however, we find that the entanglement velocity is generically smaller than 1. We use these properties to find a closed-form expression for the entanglement-membrane line tension.
我们研究了量子信息在最近引入的一类砌砖量子电路中的传播，这类电路推广了双酉类。这些电路在时间上是酉的，而它们的空间动力学仅在一个受限子空间中是酉的。首先，我们表明局部算符像在双酉电路中一样以光速传播，即蝴蝶速度取电路几何结构所允许的最大值。然后，我们证明对于一族兼容的初始态（实际上，对于双酉电路兼容族的一个扩展），纠缠传播仍然可以精确地表征，并且渐近纠缠斜率再次与雷尼指数无关。然而，值得注意的是，我们发现纠缠速度通常小于1。我们利用这些性质找到了纠缠膜线张力的一个封闭形式表达式。
