A 350-year-old theorem reveals new properties of light waves
Ever since Isaac Newton and Christiaan Huygens first debated the nature of light in the 17th century, scientists have puzzled over whether light is best thought of as a wave or a particle: perhaps even both at the quantum level.
Now, researchers at Stevens Institute of Technology have revealed a new link between the two views, using a 350-year-old mechanical theorem: commonly used to describe the motion of large physical objects such as pendulums and planets, to explain some of the most complex behavior of light waves.
"Bridging coherence optics and classical mechanics: a generic light polarization-entanglement complementary relation."
The work, led by Xiao-Feng Qian, assistant professor of physics at Stevens Institute of Technology, and published in the Aug. 17 online issue of Physical Review Research, also demonstrates for the first time that the degree of nonquantum entanglement of light waves and their degree of polarization have a direct complementary relationship: as one rises, the other falls, so that the degree of entanglement can be inferred directly from the degree of polarization, and vice versa. This means that difficult-to-measure optical properties such as amplitude, phase and correlation, and even those of quantum wave systems, can be deduced from something that is much easier to measure: the intensity of light.
Xiao-Feng Qian said, "For more than a century, we have known that light sometimes behaves like a wave and sometimes like a particle, but reconciling the two frames has proven extremely difficult, and our work does not solve this problem; but it does show that there is a deep connection between the wave and particle concepts not only at the quantum level, but also at the level of classical light waves and point mass systems Both are deeply connected."
Xiao-Feng Qian's team used a mechanics theorem originally proposed by Huygens in a 1673 book on pendulums, which explains how the amount of energy required to rotate an object varies with the object's mass and axis of rotation. "It's a well-established mechanical theorem that explains how physical systems like clocks or prosthetics work. But we were able to show that it can also provide new insights into how light works."
The 350-year-old theorem describes the relationship between masses and their rotational momentum, so how can it be applied to light when there is no mass to measure?Xiao-Feng Qian's team interpreted the intensity of light as equivalent to the mass of a physical object, and then mapped those measurements to a coordinate system that can be explained by the Huygens Mechanics theorem.Xiao-Feng Qian explains, "Essentially, we found a way to transform an optical system so that we could visualize it as a mechanical system and then describe it with well-established physical equations."
Once the team visualized light waves as part of a mechanical system, new connections between the properties of the light waves became immediately apparent - including a clear relationship between entanglement and polarization.
Mapping optical polarization coherence and entanglement of arbitrary 3D light fields to geometric illustrations of COM and MOI mechanical concepts.
Geometric illustration of the mapping of optical polarization coherence and entanglement of arbitrary 2D optical beams and 4D generic structural fields to COM and MOI mechanical concepts.
"This has never been shown before, but once the properties of light are mapped onto a mechanical system, it becomes very clear. What was once abstract becomes concrete: using the mechanical equations, the distance between the 'center of mass' and other mechanical points can be measured realistically, thus showing the relationship between the different properties of light."
Clarifying these relationships could have important practical implications, Xiao-Feng Qian explains, allowing subtle and difficult-to-measure properties of optical, and even quantum, systems to be deduced from simpler, more reliable measurements of light intensity. More speculatively, the team's findings suggest that it is possible to use mechanical systems to model and better understand the strange and complex behavior of quantum wave systems.
Of the results, the team said, "It is still ahead of us, but with this first study, we have clearly shown that it is possible to understand optical systems in a completely new way by applying mechanical concepts. Ultimately, this research helps simplify the way we understand the world by allowing us to recognize the intrinsic connections between apparently unrelated laws of physics."
Reference link:
[1]https://phys.org/news/2023-08-physicists-year-old-theorem-reveal-properties.html
[2]https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.5.033110
[3]https://www.eurekalert.org/news-releases/999164
