Ljubotina Marko, Zadnik Lenart, Prosen Tomaž
Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia.
Phys Rev Lett. 2019 Apr 19;122(15):150605. doi: 10.1103/PhysRevLett.122.150605.
We demonstrate ballistic spin transport of an integrable unitary quantum circuit, which can be understood either as a paradigm of an integrable periodically driven (Floquet) spin chain, or as a Trotterized anisotropic (XXZ) Heisenberg spin-1/2 model. We construct an analytic family of quasilocal conservation laws that break the spin-reversal symmetry and compute a lower bound on the spin Drude weight, which is found to be a fractal function of the anisotropy parameter. Extensive numerical simulations of spin transport suggest that this fractal lower bound is in fact tight.
我们展示了一个可积酉量子电路的弹道自旋输运，它既可以被理解为一个可积周期性驱动（弗洛凯）自旋链的范例，也可以被理解为一个经 Trotter 化的各向异性（XXZ）海森堡自旋 - 1/2 模型。我们构建了一族打破自旋反转对称性的准局域守恒定律，并计算了自旋德鲁德权重的下限，发现它是各向异性参数的分形函数。自旋输运的大量数值模拟表明，这个分形下限实际上是严格的。
