近日，瑞士苏黎世联邦理工学院的Christian Carisch与德国康斯坦大学的Oded Zilberberg以及英国兰卡斯特大学的Alessandro Romito合作并取得一项新进展。经过不懈努力，他们揭示量子测量读出效率对系统纠缠的影响。相关研究成果已于2024年8月12日在国际知名学术期刊《物理评论A》上发表。

本文中，研究人员使用一种混合态纠缠度量——构型相干性，量化了一维（1D）量子随机游走中粒子在低效监控下的纠缠。研究人员发现，测量诱导的量子-经典交叉点的系统最大平均纠缠会受到测量强度和测量效率的不同程度抑制。原则上，强测量可以无限降低纠缠量。

但是，在给定测量强度下，高效的读出可以显著提高系统纠缠，使得高保真度探测器对于成功的量子计算至关重要。这项研究结果对众多领域具有影响，从量子随机游走模拟平台到测量诱导相变相关问题。

据悉，受监控的量子系统沿着与观察者对该系统状态的了解相关的随机轨迹演化。在这种动态下，某些量子资源（如纠缠）可能取决于观察者的知识状态。

附：英文原文

Title: Effect of the readout efficiency of quantum measurement on the system entanglement

Author: Christian Carisch, Oded Zilberberg, Alessandro Romito

Issue&Volume: 2024/08/12

Abstract: Monitored quantum systems evolve along stochastic trajectories correlated with the observer's knowledge of the system's state. Under such dynamics, certain quantum resources like entanglement may depend on the observer's state of knowledge. Here, we quantify the entanglement for a particle on a one-dimensional (1D) quantum random walk under inefficient monitoring using a mixed state-entanglement measure: the configuration coherence. We find that the system's maximal mean entanglement at the measurement-induced quantum-to-classical crossover is suppressed in different ways by the measurement strength and inefficiency. In principle, strong measurements can lower the amount of entanglement indefinitely. However, at a given measurement strength, efficient readout can crucially increase the system entanglement, making high-fidelity detectors essential for successful quantum computing. Our results bear impact for a broad range of fields, ranging from quantum simulation platforms of random walks to questions related to measurement-induced phase transitions.

DOI: 10.1103/PhysRevA.110.022214

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.022214