Quantum effects in the interference of photon number states

TL;DR

This paper explores the quantum physics behind multi-photon interference in a two-path interferometer, revealing how the interference pattern's periodicity relates to the weak value of the unobserved intensity difference, bridging classical and quantum perspectives.

Contribution

It demonstrates that the periodicity of multi-photon interference is connected to the weak value of the unobserved intensity difference, providing a new understanding of quantum interference patterns.

Findings

Interference periodicity linked to weak value of intensity difference

Operator relations determine quantum interference patterns

Connects classical causality with quantum superposition phenomena

Abstract

Multi-photon interference results in modulations of output probabilities with phase shift periods that are much shorter than 2 Pi. Here, we investigate the physics behind these statistical patterns in the case of well-defined photon numbers in the input and output modes of a two-path interferometer. We show that the periodicity of the multi-photon interference is related to the weak value of the unobserved intensity difference between the two arms of the interferometer. This means that the operator relations between the photon number differences in input, path, and output can be used to determine the periodicity of the experimentally observed quantum interference, establishing an important link between the classical causality of random phase interference and quantum effects that depend on the superposition of classically distinct possibilities.