Physics Department

The research of Xiaofeng Qian, an assistant professor in the Department of Physics, and Misagh Izadi ’23, a research assistant with the Stevens Center for Quantum Science and Engineering, has been featured on the website of Physics World, the monthly publication of the U.K.-based professional membership society Institute of Physics. Izadi received his master’s degree in physics from Stevens in May 2023.

Titled “Bridging Coherence Optics and Classical Mechanics: A Generic Light Polarization-Entanglement Complementary Relation,” Qian and Izadi’s research establishes the first quantitative relationship between mechanics (the study of the motion of physical bodies) and optics (the study of light). Their research was published in the August 17 online issue of the American Physical Society’s Physical Review Research.

The work proves for the first time that a light wave’s degree of non-quantum entanglement (how systems remain connected despite their distance or any barriers) exists in a direct and complementary relationship with its degree of polarization (the direction of vibration of light waves). As one rises, the other falls, enabling the level of entanglement to be inferred directly from the level of polarization, and vice versa. This means that hard-to-measure optical properties such as amplitudes, phases and correlations can be deduced by measuring light intensity.

The discovery leverages two seemingly unrelated theories by 17th-century Dutch scientist Christiaan Huygens: that light is a wave (in contrast to Isaac Newton’s theory that light behaves like particles) and a mechanical theorem published in a 1673 book on pendulums, that explains how the energy required to rotate an object varies depending on the object’s mass and the axis around which it turns.

Although still theoretical, Qian and Izadi’s breakthrough fundamentally connects light wave features with mechanical mass concepts for the first time and deepens the fundamental understanding of both optics and mechanics. It provides a visual mechanical interpretation of the intriguingly abstract concept of entanglement, which in turn shows exciting promise for impact in quantum information, computation and simulation.

Qian and Izadi’s research paves the way for a fresh view of wave optics and mechanics. Its potential impact reaches across and beyond these diverse disciplines, offering new avenues for research, exploration and education in both classical and quantum physics.