Klauck Friederike U J, Heinrich Matthias, Szameit Alexander, Wolterink Tom A W
Institute of Physics, University of Rostock, Rostock, Germany.
Sci Adv. 2025 Jan 10;11(2):eadr8275. doi: 10.1126/sciadv.adr8275. Epub 2025 Jan 8.
Exceptional points facilitate peculiar dynamics in non-Hermitian systems. Yet, in photonics, they have mainly been studied in the classical realm. In this work, we reveal the behavior of two-photon quantum states in non-Hermitian systems across the exceptional point. We probe the lossy directional coupler with an indistinguishable two-photon input state and observe distinct changes of the quantum correlations at the output as the system undergoes spontaneous breaking of parity-time symmetry. Moreover, we demonstrate a switching in the quantum interference of photons directly at the exceptional point, where Hong-Ou-Mandel dips are transformed into peaks by a change of basis. These results show that quantum interference and exceptional points are linked in curious ways that can now be further explored.
例外点促进了非厄米系统中的特殊动力学。然而，在光子学中，它们主要是在经典领域中进行研究的。在这项工作中，我们揭示了非厄米系统中双光子量子态在例外点处的行为。我们用一个不可区分的双光子输入态探测有损耗的定向耦合器，并观察到随着系统经历宇称-时间对称性的自发破缺，输出端量子关联的明显变化。此外，我们直接在例外点处展示了光子量子干涉的切换，其中通过基的变化，Hong-Ou-Mandel凹陷转变为峰值。这些结果表明，量子干涉和例外点以奇特的方式联系在一起，现在可以进一步探索。
