Introducing wave-particle duality with a common path interferometer

A novel approach to illustrate wave-particle duality is presented, utilizing a common-path interferometer (CPI), which is particularly suitable for university quantum mechanics teaching. The CPI is a phase-stable interferometer composed of two half-wave plates, a quarter-wave plate, and polarization beam splitters. Unlike traditional interferometers that rely on spatial-mode interference, the CPI operates through interference between two polarization modes, guaranteeing the same optical path without the need for phase lock-in. This design produces stable interference patterns with high visibility, which is an ideal tool for undergraduate experimental demonstration of wave-particle duality. Therefore, this straightforward table-top experimental setup can be effectively integrated into university quantum mechanics courses and serves as a valuable platform for introducing cutting-edge physics concepts into college physics education.