Qubit Entanglement Driven by Remote Optical Fields

We examine the entanglement between two qubits, supposed to be remotely located and driven by independent quantized optical fields. No interaction is allowed between the qubits, but their degree of entanglement changes as a function of time. We report a collapse and revival of entanglement that is similar to the collapse and revival of single-atom properties in cavity QED.Comment: v3, major changes, published in Optics Letter

Entanglement Polygon Inequality in Qubit Systems

We prove a set of tight entanglement inequalities for arbitrary $N$-qubit pure states. By focusing on all bi-partite marginal entanglements between each single qubit and its remaining partners, we show that the inequalities provide an upper bound for each marginal entanglement, while the known monogamy relation establishes the lower bound. The restrictions and sharing properties associated with the inequalities are further analyzed with a geometric polytope approach, and examples of three-qubit GHZ-class and W-class entangled states are presented to illustrate the results.Comment: 8 pages, 4 figure

Analysis of Nonsequential Double Ionization Using Virtual Detector Theory with Path Summation

We apply the virtual detector method, which is based on non-destructive numerical quantum detections and the propagation of Bohmian-like classical particles, to study in an ab initio way the nonsequential ionization dynamics of a model two-electron atom with helium character. Single- and double-ionization events are characterized and displayed using detector signals measured at different points in the two-electron two-dimensional position-space. The double photoelectron momentum distribution is calculated via coherent path-summation over virtual particle trajectories. Insights into different ionization and electron recollision pathways are gained from detailed virtual particle tracking and energy-time readouts. This study demonstrates a new extension of our application of virtual detector theory to strong-field multi-electron quantum dynamics.Comment: 6 pages, 6 figures, 1 tabl