# Double-slit interferometry as a lossy beam splitter

## TL;DR

This paper models double-slit diffraction as a lossy beam splitter within a quantum framework, enabling potential applications in high-dimensional quantum information processing and offering a robust, miniaturizable alternative to traditional interferometry.

## Contribution

It introduces a novel framework for describing diffraction-based interferometry as a post-selected unitary transformation suitable for quantum information processing.

## Key findings

- Diffraction can be represented as an infinite-dimensional transformation.
- Post-selection truncates the transformation to a finite-dimensional lossy beam splitter.
- Classical diffraction optics can be extended to quantum information applications.

## Abstract

We cast diffraction-based interferometry in the framework of post-selected unitary description towards enabling it as a platform for quantum information processing. We express slit-diffraction as an infinite-dimensional transformation and truncate it to a finite-dimensional transfer matrix by post-selecting modes. Using such a framework with classical fields, a customized double-slit setup is effectively a lossy beam splitter in a post-selected sense. Diffraction optics provides a robust alternative to conventional multi-beam interferometry with scope for miniaturization, and also has applications in matter wave interferometry. In this work, the classical treatment sets the stage for quantization of fields and implementing higher dimensional quantum information processing like that done with other platforms such as orbital angular momentum.