Synthesis of the Einstein-Podolsky-Rosen entanglement in a sequence of two single-mode squeezers

TL;DR

This paper presents a novel, stable method for synthesizing Einstein-Podolsky-Rosen entangled states using two back-to-back single-pass squeezers and waveplates, avoiding phase stabilization issues and demonstrating a 1.4 dB two-mode squeezed state.

Contribution

The authors introduce a new scheme for EPR entanglement generation that simplifies stabilization and enhances practicality, demonstrated experimentally with measurable squeezing.

Findings

Generated a 1.4 dB two-mode squeezed state.

Eliminated the need for active phase stabilization.

Successfully characterized the entangled state via homodyne tomography.

Abstract

Synthesis of the Einstein-Podolsky-Rosen entangled state --- the primary entangled resource in continuous-variable quantum-optical information processing --- is a technological challenge of great importance. Here we propose and implement a new scheme of generating this state. Two nonlinear optical crystals, positioned back-to-back in the waist of a pump beam, function as single-pass degenerate optical parametric amplifiers and produce single-mode squeezed vacuum states in orthogonal polarization modes, but in the same spatiotemporal mode. A subsequent pair of waveplates acts as a beam splitter, entangling the two polarization modes to generate the Einstein-Podolsky-Rosen state. This technique takes advantage of the strong nonlinearity associated with type-I phase-matching configuration while at the same time eliminating the need for actively stabilizing the optical phase between the two squeezers, which typically arises if these squeezers are spatially separated. We demonstrate our method in an experiment, preparing a 1.4 dB two-mode squeezed state and characterizing it via two-mode homodyne tomography.