Entanglement Phase Transitions in Measurement-Only Dynamics
Entanglement Phase Transitions in Measurement-Only Dynamics
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DOI：
10.1103/physrevx.11.011030
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发表时间：
2021-02-15
影响因子：
12.5
通讯作者：
Khemani, Vedika
中科院分区：
文献类型：
--
作者：
Ippoliti, Matteo;Gullans, Michael J.;Khemani, Vedika
重复投影测量的酉电路可以经历作为测量速率的函数的纠缠相变（EPT）。这种转变通常被理解为酉动力学的扰乱效应和测量的解纠缠效应之间的竞争。我们发现，令人惊讶的是，EPTS是可能的，即使在没有混乱的酉动态，在那里他们最好的理解为产生单独的测量。这一发现促使我们引入仅测量的模型，其中驱动EPT的“扰乱”和“整理”效应从根本上交织在一起，不能归因于物理上不同的过程。这些模型代表了一种新形式的EPT，概念上不同于在混合酉投射电路。我们探讨的纠缠相图，临界点，和量子代码的性质，这些仅测量模型。我们发现，在这些模型中的EPT驱动的原则是挫折，或相互不兼容的测量。令人惊讶的是，当测量足够长但仍然是局部的（大于或类似于三体）算子时，纠缠（体积定律）相是通用的结果。我们确定了一类例外，这种行为（“二分合奏”），不能维持纠缠阶段，但显示双面积法阶段，可能与不同种类的量子秩序，分离的自对偶临界点。最后，我们介绍了一种测量的信息传播的动态和使用它来证明一个统计光锥的出现，尽管量子测量固有的非局部性。
Unitary circuits subject to repeated projective measurements can undergo an entanglement phase transition (EPT) as a function of the measurement rate. This transition is generally understood in terms of a competition between the scrambling effects of unitary dynamics and the disentangling effects of measurements. We find that, surprisingly, EPTs are possible even in the absence of scrambling unitary dynamics, where they are best understood as arising from measurements alone. This finding motivates us to introduce measurement-only models, in which the "scrambling" and "unscrambling" effects driving the EPT are fundamentally intertwined and cannot be attributed to physically distinct processes. These models represent a novel form of an EPT, conceptually distinct from that in hybrid unitary-projective circuits. We explore the entanglement phase diagrams, critical points, and quantum code properties of some of these measurement-only models. We find that the principle driving the EPTs in these models is frustration, or mutual incompatibility, of the measurements. Surprisingly, an entangling (volume-law) phase is the generic outcome when measuring sufficiently long but still local (greater than or similar to 3-body) operators. We identify a class of exceptions to this behavior ("bipartite ensembles") which cannot sustain an entangling phase but display dual area-law phases, possibly with different kinds of quantum order, separated by self-dual critical points. Finally, we introduce a measure of information spreading in dynamics with measurements and use it to demonstrate the emergence of a statistical light cone, despite the nonlocality inherent to quantum measurements.