# Evolution of Photon Beams through a Nested Mach-Zehnder Interferometer using Classical States of Light

## TL;DR

This paper introduces a classical state-vector method to explain the behavior of photon beams in nested Mach-Zehnder interferometers, demonstrating that quantum experiment results can be understood within standard quantum mechanics using classical light states.

## Contribution

The paper presents a novel classical state-vector approach to analyze nested interferometers, clarifying experimental results previously considered counterintuitive within quantum mechanics.

## Key findings

- Results align with standard quantum mechanics predictions.
- Classical states can explain complex interferometric outcomes.
- Power spectrum analysis confirms classical explanation validity.

## Abstract

In this paper, we present a coherent state-vector method which can explain the results of a nested linear Mach-Zehnder Interferometric experiment. Such interferometers are used widely in Quantum Information and Quantum Optics experiments and also in designing quantum circuits. We have specifically considered the case of an experiment by Danan \emph{et al.} (Phys. Rev. Lett. \textbf{111}, 240402 (2013)) where the outcome of the experiment was spooky by our intuitive guesses. However we have been able to show by our method that the results of this experiment is indeed expected within the standard formalism of Quantum Mechanics using any classical state of a single-mode radiation field as the input into the nested interferometric set-up of the aforesaid experiment and thereby looking into the power spectrum of the output beam.