近日，清华大学的付星及其研究小组与新加坡南洋理工大学的Yijie Shen等人合作并取得一项新进展。经过不懈努力，他们对量子压缩态的结构光类比进行研究。相关研究成果已于2024年10月21日在国际知名学术期刊《光：科学与应用》上发表。

该研究团队通过利用经典结构光构建量子压缩态的类比，进一步发展了这一范式。研究发现，在量子光学中，负责突破标准量子极限的压缩机制，同样能使经典光学超越“标准空间极限”：光束可以在实际空间的一个横向方向上被“压缩”（而另一个正交方向则会扩大），使其宽度小于相应的基础高斯模式的宽度。

研究人员证明了经典压缩能够实现接近亚衍射和超振荡的光聚焦，同时伴随着实验中（模拟中）展示的约为λ/100（λ/1000）量级的纳米级相位梯度。至关重要的是，通过改变压缩参数，压缩机制允许对这两个特性进行连续调节，从而为超越衍射极限的光学显微镜和计量学提供了独特的灵活性，并提示应进一步探索量子效应的经典类比。

据悉，量子光学加深了人们对光本质的理解，并实现了远超经典光所能达到的应用。量子光的独特能力激发了将一些概念性思想迁移到经典光学领域，重点在于复制和利用离散变量系统的非平凡量子态。

附：英文原文

Title: Structured light analogy of quantum squeezed states

Author: Wang, Zhaoyang, Zhan, Ziyu, Vetlugin, Anton N., Ou, Jun-Yu, Liu, Qiang, Shen, Yijie, Fu, Xing

Issue&Volume: 2024-10-21

Abstract: Quantum optics has advanced our understanding of the nature of light and enabled applications far beyond what is possible with classical light. The unique capabilities of quantum light have inspired the migration of some conceptual ideas to the realm of classical optics, focusing on replicating and exploiting non-trivial quantum states of discrete-variable systems. Here, we further develop this paradigm by building the analogy of quantum squeezed states using classical structured light. We have found that the mechanism of squeezing, responsible for beating the standard quantum limit in quantum optics, allows for overcoming the “standard spatial limit” in classical optics: the light beam can be “squeezed” along one of the transverse directions in real space (at the expense of its enlargement along the orthogonal direction), where its width becomes smaller than that of the corresponding fundamental Gaussian mode. We show that classical squeezing enables nearly sub-diffraction and superoscillatory light focusing, which is also accompanied by the nanoscale phase gradient of the size in the order of λ/100 (λ/1000), demonstrated in the experiment (simulations). Crucially, the squeezing mechanism allows for continuous tuning of both features by varying the squeezing parameter, thus providing distinctive flexibility for optical microscopy and metrology beyond the diffraction limit and suggesting further exploration of classical analogies of quantum effects.

DOI: 10.1038/s41377-024-01631-x

Source: https://www.nature.com/articles/s41377-024-01631-x