Revealing measurement-induced phase transitions by pre-selection
Revealing measurement-induced phase transitions by pre-selection
复制标题
通过预选揭示测量引起的相变
DOI：
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
S. Diehl
中科院分区：
文献类型：
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作者：
M. Buchhold;T. Muller;S. Diehl
最近发现的测量诱导相和相变推动了对受控量子平台中一般非幺正动力学的理解。到目前为止，这些跃迁在很大程度上仍然是难以捉摸的，因为由于测量结果的随机性，它们在标准的量子力学观测中被掩盖了。在这里，我们建立了一个通用的方案-预选-使它们可观察：结果的随机性被明确打破转向系统的代表性状态，这对应于指数许多可能的测量结果之一。值得注意的是，这种转向可以选择得如此温和，以至于基本的测量诱导跃迁的基本性质，如纠缠结构和临界指数，不会被修改。预选引入了一个独特的黑暗或吸收状态与宏观秩序，取代最大的混合定态的无条件测量轨迹合奏。这就建立了一个由测量引起的相变到新形式的量子吸收态跃迁的联系，这种跃迁可以通过局部序参量用标准方法检测到。这种洞察力进一步实现了量子模拟策略，确定了最先进的量子平台中的基本普适性类，而无需测量读数。
Pushing forward the understanding of general non-unitary dynamics in controlled quantum platforms has been fueled by the recent discovery of measurement-induced phases and phase transitions. So far, these transitions remained largely elusive, since they are masked in standard quantum mechanical observables due to the randomness of measurement outcomes. Here, we establish a general scheme -- pre-selection -- to make them observable: The outcome randomness is broken explicitly by steering the system towards a representative state, which corresponds to one out of exponentially many possible measurement outcomes. Remarkably, this steering can be chosen so gently that the basic properties of the underlying measurement-induced transition, such as entanglement structure and critical exponents, are not modified. Pre-selection introduces a unique dark or absorbing state with macroscopic order, replacing the maximally mixed stationary state of the unconditioned measurement trajectory ensemble. This creates a link of measurement-induced phase transitions to new forms of quantum absorbing state transitions, which can be detected by standard means via a local order parameter. This insight further enables a quantum simulation strategy, determining the underlying universality class in state-of-the-art quantum platforms without measurement readout.