Tunable quantum interference: How to make morning, noon, and afternoon states

TL;DR

This paper demonstrates how to generate and control N-photon states with tunable quantum interference, transitioning from phase squeezing to path entanglement using a single parameter, visualized through a spin analogy.

Contribution

It introduces a method to characterize and tune N-photon states produced by interference between laser and downconverted light in a two-path interferometer.

Findings

States can be tuned from phase squeezing to maximal entanglement

Single parameter controls the transition between different quantum states

States visualized using a spin-N/2 algebra analogy

Abstract

We show that the N-photon states produced by interference between laser light and downconverted light at the input of a two path interferometer can be characterized by a single tuning parameter that describes a transition from phase squeezing to nearly maximal path entanglement and back. The quantum states are visualized on a sphere using the analogy between N-photon interference and the spin-N/2 algebra.