Introducing wave–particle duality with a common path interferometer

Abstract A novel pedagogical approach to illustrate wave–particle duality is presented, utilizing a common-path interferometer (CPI), which is particularly suitable for university quantum mechanics (QM) 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 locking. 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 QM courses and serves as a valuable platform for introducing cutting-edge physics concepts into college physics education.