Harmonic entanglement in a degenerate parametric down conversion

TL;DR

This paper investigates harmonic entanglement and squeezing in a two-mode radiation generated via degenerate parametric down conversion, revealing quadrature entanglement and enhanced properties with increased external coherent light.

Contribution

It demonstrates the presence of quadrature entanglement between fundamental and second-harmonic modes and shows how entanglement strength increases with external coherent light, distinct from squeezing.

Findings

Quadrature entanglement exists between fundamental and second-harmonic modes.

Superimposed radiation exhibits significant two-mode squeezing.

Entanglement strengthens with increased external coherent light.

Abstract

We study the harmonic entanglement and squeezing in a two-mode radiation produced in a degenerate parametric down conversion process coupled to a two-mode vacuum reservoir employing the linearization procedure. It is found that there is a quadrature entanglement between the harmonically related fundamental and second-harmonic modes and the superimposed radiation exhibits a significant two-mode squeezing. The entanglement exits even when there is no two-mode squeezing, since the correlation leading to these phenomena are essentially different. In addition, the more the external coherent light is down converted, the more stronger the entanglement and mean photon number of the two-mode radiation would be which is not generally true for squeezing.