论文标题
部分可观测时空混沌系统的无模型预测
Hierarchy of topological order from finite-depth unitaries, measurement and feedforward
论文作者
论文摘要
远程纠缠 - 拓扑秩序的状态的骨干 - 使用当地的统一电路或等效地制成绝热状态准备在有限的时间内创建。最近,已经揭示了单个站点测量可提供漏洞,在某些情况下可以进行有限的状态准备。在这里,我们展示了这种观察如何根据创建状态所需的测量层数量最少,在远程纠缠状态下施加复杂性层次结构,我们称之为“镜头”。首先,类似于Abelian稳定器状态,我们构建了单杆协议,用于创建具有nilpotency二级的任何非阿布尔量子双重双重(例如$ d_4 $或$ q_8 $)。我们表明,在测量之后,波函数始终崩溃到所需的非亚伯拓扑顺序中,条件是记录测量结果。此外,可以通过馈电量确定性地制备清洁量子双基态,这取决于测量结果。其次,我们提供了第一个建设性的证据,即有限数量的镜头可以为任何可解决的对称组实现Kramers-Wannier二重性转换(即测量映射)。作为一种特殊情况,这提供了一个明确的协议,可以为所有可解决的组准备扭曲的量子双重。第三,我们认为某些拓扑顺序(例如不可溶解的量子双倍或斐波那契)定义了物质的非平凡阶段,这些阶段不能由有限的深度单位和测量,这些阶段不能由任何有限数量的镜头制备。此外,我们探讨了允许门具有指数式小尾巴的后果,例如,在包括手性理论(包括手性的理论)的任何Abelian Anyon理论上都可以制备。该层次结构描绘了远程纠缠状态的景观的新图片,对量子模拟器产生了实际影响。
Long-range entanglement--the backbone of topologically ordered states--cannot be created in finite time using local unitary circuits, or equivalently, adiabatic state preparation. Recently it has come to light that single-site measurements provide a loophole, allowing for finite-time state preparation in certain cases. Here we show how this observation imposes a complexity hierarchy on long-range entangled states based on the minimal number of measurement layers required to create the state, which we call "shots". First, similar to Abelian stabilizer states, we construct single-shot protocols for creating any non-Abelian quantum double of a group with nilpotency class two (such as $D_4$ or $Q_8$). We show that after the measurement, the wavefunction always collapses into the desired non-Abelian topological order, conditional on recording the measurement outcome. Moreover, the clean quantum double ground state can be deterministically prepared via feedforward--gates which depend on the measurement outcomes. Second, we provide the first constructive proof that a finite number of shots can implement the Kramers-Wannier duality transformation (i.e., the gauging map) for any solvable symmetry group. As a special case, this gives an explicit protocol to prepare twisted quantum double for all solvable groups. Third, we argue that certain topological orders, such as non-solvable quantum doubles or Fibonacci anyons, define non-trivial phases of matter under the equivalence class of finite-depth unitaries and measurement, which cannot be prepared by any finite number of shots. Moreover, we explore the consequences of allowing gates to have exponentially small tails, which enables, for example, the preparation of any Abelian anyon theory, including chiral ones. This hierarchy paints a new picture of the landscape of long-range entangled states, with practical implications for quantum simulators.