Impact of Polarization Distinguishability on Coherence in QIUP

TL;DR

This paper investigates how polarization distinguishability at the source affects interference in quantum imaging with undetected photons, showing that post-generation optical elements cannot restore lost coherence caused by polarization differences.

Contribution

It demonstrates that polarization distinguishability at the source irreversibly reduces interference in QIUP, emphasizing the importance of source indistinguishability for coherence.

Findings

Polarization distinguishability at the source leads to interference loss.

Post-generation optical elements cannot recover lost interference.

Indistinguishability at the source is crucial for coherence in QIUP.

Abstract

Quantum imaging with undetected photons (QIUP) is a promising technique for non-invasive imaging, particularly at wavelengths where detectors are inefficient or unavailable. Recent studies have investigated the role of polarization in QIUP schemes. In this work, we examine whether post-generation optical elements can recover interference when the signal photons are distinguishable in polarization at the source. Specifically, we employ a Mach-Zehnder interferometer after the photon pairs are generated from two nonlinear crystals. Our results indicate that polarization distinguishability at the time of generation leads to a loss of interference that cannot be restored by post-generation optical arrangements. This highlights the fundamental importance of indistinguishability at the source for maintaining coherence in QIUP systems.