Weinstein Zack, Bao Yimu, Altman Ehud
Department of Physics, University of California, Berkeley, California 94720, USA.
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Phys Rev Lett. 2022 Aug 19;129(8):080501. doi: 10.1103/PhysRevLett.129.080501.
Generic many-body systems coupled to an environment lose their quantum entanglement due to decoherence and evolve to a mixed state with only classical correlations. Here, we show that measurements can stabilize quantum entanglement within open quantum systems. Specifically, in random unitary circuits with dephasing at the boundary, we find both numerically and analytically that projective measurements performed at a small nonvanishing rate result in a steady state with an L^{1/3} power-law scaling entanglement negativity within the system. Using an analytical mapping to a statistical mechanics model of directed polymers in a random environment, we show that the power-law negativity scaling can be understood as Kardar-Parisi-Zhang fluctuations due to the random measurement locations. Further increasing the measurement rate leads to a phase transition into an area-law negativity phase, which is of the same universality as the entanglement transition in monitored random circuits without decoherence.
与环境耦合的一般多体系统由于退相干而失去量子纠缠，并演化为仅具有经典关联的混合态。在这里，我们表明测量可以稳定开放量子系统内的量子纠缠。具体而言，在边界处有退相的随机酉电路中，我们通过数值和解析方法发现，以小的非零速率进行的投影测量会导致系统内具有(L^{1/3})幂律标度纠缠负性的稳态。通过对随机环境中定向聚合物的统计力学模型进行解析映射，我们表明幂律负性标度可以理解为由于随机测量位置导致的 Kardar-Parisi-Zhang 涨落。进一步提高测量速率会导致相变到面积律负性相，这与无退相干的受监测随机电路中的纠缠相变具有相同的普适性。
