Decoherence remains one of the most serious challenges to the implementation of quantum technology. It appears as a result of the transformation over time of a quantum superposition state into a classical mixture due to the quantum system interacting with the environment. Since quantum systems are never completely isolated from their environment, decoherence therefore cannot be avoided in realistic situations. Decoherence has been extensively studied, mostly theoretically, because it has many important implications in quantum technology, such as in the fields of quantum information processing, quantum communication, and quantum computation. Here we report a novel experimental scheme on the study of decoherence of a two-mode squeezed vacuum state via its second harmonic generation signal. Our scheme can directly extract the decoherence of the phase-sensitive quantum correlation $\langle \widehat{a}\widehat{b}\rangle$ between two entangled modes $a$ and $b$. Such a correlation is the most important characteristic of a two-mode squeezed state. More importantly, this is an experimental study on the decoherence effect of a squeezed vacuum state, which has been rarely investigated.

中文翻译：

---

二次谐波产生的双模压缩真空态退相干实验研究

退相干仍然是实现量子技术最严峻的挑战之一。它出现是由于量子系统与环境相互作用，量子叠加态随时间转变为经典混合物的结果。由于量子系统永远不会与环境完全隔离，因此在现实情况下无法避免退相干。退相干已被广泛研究，主要是在理论上，因为它在量子技术中具有许多重要意义，例如在量子信息处理、量子通信和量子计算领域。在这里，我们报告了一种通过二次谐波产生信号研究双模压缩真空状态退相干的新实验方案。$〈\widehat{\mathrm{一种}}\widehat{乙}〉$ 在两种纠缠模式之间 $\mathrm{一种}$ 和 $乙$. 这种相关性是双模压缩状态的最重要特征。更重要的是，这是一项关于压缩真空状态退相干效应的实验研究，很少有人对此进行研究。