________________________________________________________________________ a Physics Department, University of Connecticut, Storrs, CT, USA. *Corresponding author: E-mail: chandra.roychoudhuri@uconn.edu; Chapter 8 Print ISBN: 978-81-19217-29-8, eBook ISBN: 978-81-19217-05-2 The Double-Slit & the Mach-Zehnder Interferometer: Re-visiting through Asymmetry Chandrasekhar Roychoudhuri a* DOI: 10.9734/bpi/fraps/v3/6355A ABSTRACT It is generally believed that the “mystery” behind understanding Quantum Mechanics (QM) and the global drives to construct quantum computers using “Entanglement”, can be understood from how the two-beam superposition effect (SE) emerges out of a 2-slit, and a Mach-Zehnder Interferometer (MZI). This chapter rehabilitates the classical analyses of these two superposition effects, while exploiting functional asymmetries, either deliberately introduced or intrinsic in the two-beam apparatuses. We are using mathematical formalism already well-established in classical optics since 1800’s, but with the extra emphasis that any final data generation requires some real physical interaction between the detector and the two light signals simultaneously stimulating the detecting molecules. This critical step of physical interaction process is not explicitly underscored by either the classical or the quantum physics. However, the asymmetry, either in the propagation or in the interaction process, is utilized to bring out the contradictions with the QM interpretations. For the 2-slit system, we deliberately introduce asymmetry on one of the slits. For MZI, the asymmetry is already built into the classical reflection property of a typical beams splitter. Keywords: Asymmetry; interferometer: quantum mechanics; mach-zehnder. 1. INTRODUCTION During the late 1600’s, there was a debate on the wave-particle-duality (WPD) between Newton (proponent of “corpuscular” model) and Huygens (proponent of “non-interacting secondary wavelets” model). It remained unresolved because, as Newton had put it, none of them understood the fundamental nature of light. Even today we are still grappling to bridge the gap between the quantized emission of energy from atoms and the propagation of this energy as classical Maxwellian wave amplitudes. However, Newton’s superior fame preserved the