Unconditional remote entanglement using second-harmonic generation and twin two-mode squeezed vacuum states

TL;DR

This paper introduces a novel continuous-variable remote entanglement scheme using second-harmonic generation and twin two-mode squeezed states, avoiding the need for measurement-based conditioning.

Contribution

It presents a new photonics-based method for unconditional remote entanglement leveraging second-order nonlinear interactions without state-projective measurements.

Findings

Entanglement established between second-harmonic mode and idler subsystem.

No measurement conditioning required for entanglement formation.

Utilizes fully quantum mechanical model of second harmonic generation.

Abstract

We propose a photonics-based, continuous-variable (CV) form of remote entanglement utilizing strictly second-order nonlinear optical interactions that does not require the implementation of a state-projective measurement (i.e. remote entanglement without conditioning). This scheme makes use of two separate down-converters, wherein the corresponding nonlinear crystals are driven by strong classical fields as prescribed by the parametric approximation, as well as a fully quantum mechanical model of nondegenerate second harmonic generation (SHG) whose evolution is described by the trilinear Hamiltonian of the form $\hat{H}_{\text{shg}} = i\hbar\kappa\big(\hat{a}\hat{b}\hat{c}^{\dagger} - \hat{a}^{\dagger}\hat{b}^{\dagger}\hat{c}\big)$. By driving the SHG process with the signal modes of the two down-converters, we show entanglement formation between the generated second-harmonic mode (SH-mode) and the non-interacting joint-idler subsystem without the need for any state-reductive measurements on the interacting modes.