近日，印度Harish-Chandra研究所的Aditi Sen(De)及其研究小组与印度尼赫鲁大学的Rivu Gupta合作并取得一项新进展。经过不懈努力，他们成功产生长程耦合圆波导中的真多模纠缠。相关研究成果已于2024年3月11日在国际知名学术期刊《物理评论A》上发表。

该研究团队报道了，从产品初始状态出发，其中一个模式处于压缩（压缩相干）状态，其余模式为真空状态的情况下，一个由不同耦合强度的模式耦合组成的圆波导能够产生真多模纠缠（GME），这种纠缠状态可以通过广义几何测量（GGM）进行量化。研究人员进一步证明，在固定的耦合和压缩强度条件下，随着波导之间耦合范围的增加，结果状态的GME含量也相应增加。

尽管GGM会随着耦合强度和时间的变化出现坍塌和恢复的现象，但通过对GGM曲线下面积的测量，可以明显看出长程耦合的优势。这清晰地展示了随着耦合范围的扩大，GME呈现出增长的趋势。

此外，长程耦合在固定耦合强度的情况下，有助于产生更高的广义几何测量（GGM）值。对于包含任意数目模态的系统，研究人员在模态相互作用完全相等的条件下，成功地解析得出了GGM的精确表达式。整个分析过程均基于相空间形式进行。研究人员在耦合参数中显示了无序的建设性作用，这保证了GME的稳定产生，而不依赖于耦合强度。

附：英文原文

Title: Production of genuine multimode entanglement in circular waveguides with long-range coupling

Author: Tonipe Anuradha, Ayan Patra, Rivu Gupta, Amit Rai, Aditi Sen(De

Issue&Volume: 2024/03/11

Abstract: Starting with a product initial state, squeezed (squeezed coherent) state in one of the modes, and vacuum in the rest, we report that a circular waveguide comprising modes coupled with varying coupling strength is capable of producing genuine multimode entanglement (GME), quantified via the generalized geometric measure (GGM). We demonstrate that, for a fixed coupling and squeezing strength, the GME content of the resulting state increases as the range of couplings between the waveguides increases, although the GGM collapses and revives with the variation of coupling strength and time. The advantage of long-range coupling can be emphasized by measuring the area under the GGM curve, which clearly illustrates growing trends of GME with the increasing range of couplings. Moreover, long-range couplings help in generating a higher GGM for a fixed coupling strength. We analytically determine the exact expression of GGM for systems involving an arbitrary number of modes, when all the modes interact with each other equally. The entire analysis is performed in the phase-space formalism. We manifest the constructive effect of disorder in the coupling parameter, which promises a steady production of GME, independent of the coupling strength.

DOI: 10.1103/PhysRevA.109.032411

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.032411