350-year-old theory reveals ‘profound’ relationship between properties of light

Dutch born Christian Huygens He is perhaps one of the most famous physicists you have never heard of. His work in the late seventeenth century included the tangible and intangible realms of our universe: the nature of light, and the mechanics of moving bodies.

Among his many contributions, Huygens proposed a wave theory of light that would give rise to… Physical optics, which deals with interference, diffraction, and polarization of light. He also invented the first pendulum; The most accurate timekeeping device existed nearly 300 years ago, during the Industrial Revolution.

Few connections have been made between these two seemingly disparate fields of optics and optics Classical mechanics – So far.

A pair of physicists at Stevens Institute of Technology in New Jersey have revisited Huygens’ seminal work on the pendulum, published in 1673, and used his 350-year-old mechanical theory to reveal some new connections between some of the strangest and most fundamental elements. , properties of light.

“With this first study we have clearly shown that by applying mechanistic concepts, it is possible to understand optical systems in a completely new way.” He says Physicist Xiaofengqian.

Qian and his Stevens Institute colleague Misagh Izadi considered two properties of light in their calculations: polarization and a form of correlation known as classical, or non-quantum, entanglement.

These two characteristics reflect the strange Duality of light That permeates every pocket of our universe. In a quantum sense, light – like all forms of matter – can be described as waves rippling through space, but it is also discrete particles located at a single point.

However, this is not just a quantum phenomenon. In the classical world of gears, springs, and ticking clocks, light waves rise and fall like physical ripples on an intangible ocean, with properties associated with their ever-changing progress through space.

“We have known for more than a century that light sometimes behaves as a wave, and sometimes as a particle, but reconciling these two frameworks has proven extremely difficult.” Qian said.

“Our work does not solve this problem – but it shows that there are deep connections between wave and particle concepts not just at the quantum level, but at the level of classical light waves and point-mass systems.”

Entanglement, most commonly, is a quantum phenomenon, and simply describes correlations in the properties of objects.

For particles, this could be the spin of electrons, momentum or the position of a pair of photons. Knowing something about one of these properties of one particle tells you something about the same property of the other.

Classical entanglement also describes some correlations, just without having to consider the unstable nature of an object before measuring it.

polarization It is the directional property of a light wave that oscillates up and down, or left and right. Particles such as photons, the energy packets that make up a light beam, can also be polarized.

If a light wave oscillated, so did a pendulum, Qian and Izadi thought they might be able to use the mechanics of the latter to describe the properties of the former.

“Basically, we found a way to translate the optical system so that we can visualize it as a mechanical system, and then describe it using well-established physical equations,” Qian said. He explains.

Typically, classical mechanics is used to describe the motion of large physical objects such as pendulums and planets. For example, Huygens Parallel axis theory Describes the relationship between masses and their momentum.

Qian and Izadi conceived of light as a mechanical system to which Huygens’ parallel axis theorem could be applied, and they found a “profound” relationship: the degree of polarization of a light wave was directly related to the degree of a recently recognized property called vector space entanglement.

Qian and Izadi’s calculations indicate that when one rises, the other falls, allowing the entanglement level to be inferred directly from the polarization level, and vice versa.

“Ultimately, this research helps simplify the way we understand the world, by allowing us to recognize fundamental, fundamental connections between seemingly unrelated physical laws,” Qian said. He says.

The study was published in Physical review research.