论文标题
控制损失的收益：多量系统中可本地纠缠的界限
Controlling gain with loss: Bounds on localizable entanglement in multi-qubit systems
论文作者
论文摘要
我们研究了通过在系统其余部分上的局部测量和在此测量过程中丢失的两部分纠缠所选择的多量系统中所选子系统的纠缠量之间的关系。我们研究了许多范式的纯净状态，包括广义GHz，广义W，Dicke和广义的Dicke国家。对于广义的GHz和W状态，我们在测量之前就系统中存在的纠缠而分析了可本质的纠缠范围。同样，对于Dicke和广义的Dicke国家，我们证明，随着系统大小的增加，可本质的纠缠往往等于在测量前通过特定分区而在系统中存在的两部分纠缠。在任意多Qubit纯状态的情况下，我们以数值扩展研究。我们还通过分析确定这些结果的修改，包括所提出的边界，在这些纯状态在所有量子器上均遭受单量子相距噪声的情况。此外，我们研究了一维范式的量子自旋模型，即外部场中的横向场XY模型和XXZ模型，并在数值上证明了局部纠缠对丢失的纠缠的二次依赖性。我们表明，即使在外部场的强度中存在无序的情况下，这种关系也是牢固的。
We investigate the relation between the amount of entanglement localized on a chosen subsystem of a multi-qubit system via local measurements on the rest of the system, and the bipartite entanglement that is lost during this measurement process. We study a number of paradigmatic pure states, including the generalized GHZ, the generalized W, Dicke, and the generalized Dicke states. For the generalized GHZ and W states, we analytically derive bounds on localizable entanglement in terms of the entanglement present in the system prior to the measurement. Also, for the Dicke and the generalized Dicke states, we demonstrate that with increasing system size, localizable entanglement tends to be equal to the bipartite entanglement present in the system over a specific partition before measurement. We extend the investigation numerically in the case of arbitrary multi-qubit pure states. We also analytically determine the modification of these results, including the proposed bounds, in situations where these pure states are subjected to single-qubit phase-flip noise on all qubits. Additionally, we study one-dimensional paradigmatic quantum spin models, namely the transverse-field XY model and the XXZ model in an external field, and numerically demonstrate a quadratic dependence of the localized entanglement on the lost entanglement. We show that this relation is robust even in the presence of disorder in the strength of the external field.
