Understanding of coincidence detection in Franson-type nonlocal correlations for second-order quantum superposition

TL;DR

This paper investigates the fundamental physics of nonlocal quantum correlations in Franson-type experiments by analyzing how coincidence detection and quantum superposition influence the measurement of Bell inequality violations.

Contribution

It provides a coherent analysis of how second-order quantum superposition affects nonlocal correlation fringes in coincidence detection, clarifying the role of indistinguishability and coherence.

Findings

Coincidence detection modifies measurement events based on indistinguishability.

Quantum superposition between nonlocal events is essential for nonlocal correlation fringes.

Coherence between photons is a fundamental condition for observing quantum nonlocality.

Abstract

Coincidence detection is a key technique used in nonlocal quantum-correlation measurements to test Bell inequality violation between remotely separated local detectors. With individual uniform intensity of local measurements, the nonlocal correlation fringe is a mysterious quantum feature that cannot be achieved classically. Here, the coincidence detection is coherently investigated to understand the fundamental physics of the nonlocal correlation fringe via second-order quantum superposition between selected nonlocal measurement events. Because of the coherence feature of paired photons, the coincidence technique modifies the measurement events for the rule of thumb of indistinguishability between selected measurement bases of paired photons. This indistinguishability is quantum superposition between nonlocally detected events resulting from a selected time slot of coincidence, where coherence between individually measured photons is an absolute condition.