A quantum analysis of structured classical light beams

Davıd L. Andrews

Edoardo Suerra, M. Siano, B. Paroli +4 more

Abstract We describe a monolithic interferometer for spatial coherence measurements of both classical and quantum light sources. The design enables measurements on both a PDC-based quantum source and a classical thermal source, using two identical calcite crystals to control beam alignment via birefringence. The monolithic structure ensures inherent stability. Spatial coherence is measured through temporal interferograms and spectral analysis, with both methods showing close agreement with theoretical predictions. The system is robust and performs reliably for both quantum and classical light. Its design enables automated, rapid coherence measurements across different source types.

A. Yu. Ardashev, В. А. Кашин, G. V. Skrotskiǐ

Yuanjie Yang, Yu‐Xuan Ren, Carmelo Rosales‐Guzmán

One of the applications of structured light beams which have gained significant popularity in recent time is in optical communications, at both the classical and quantum levels, either in free space or optical fibers. As such, in this chapter we provide an overview about how structured light beams are used in optical communications. The first part is devoted to the use of structured light beams in classical communications, this section is treated in three subsections where we discuss separately the cases of free space, optical fibers underwater optical channels. In the second section we delve into the use of structured light in quantum optics communications, in particular for the development of novel protocols for secure communications.

Zhaoyang Wang, Zijian Shi, Yijie Shen +2 more

Quantum-classical analogy refers to the fact that quantum and classical phenomena share a similar mathematical description and exhibit analogous behaviors, which has advanced optical frontiers. In this work, the mechanism of the squeezed state is incorporated into classical structured light, constructing a novel kind of structured light, termed the squeezed geometric beam, that is, the squeezed coherent state of geometric beams, and revealing a novel quantum-classical analogy between the noise of quantum squeezed state and the beam size of squeezed geometric beams, both evolving with the same squeezing parameter. The presented method provides an inspirational extensible framework to reveal more structured light analogies of quantum states. In addition, it is demonstrated in theory and experiment that thanks to the unveiled squeezing mechanism, the squeezed geometric beam as an information carrier can effectively lower the modal crosstalk, thus boosting the communication capacity of spatial mode multiplexing.

Thomas Konrad, Sandeep K. Goyal