Conditional measurements on multimode pairwise entangled states from spontaneous parametric downconversion

TL;DR

This paper develops a theoretical model for the multimode quantum states generated by pulsed spontaneous parametric downconversion, validated by experiments, and explores the non-Gaussian features of the conditional states for quantum information applications.

Contribution

It introduces a model based on accessible quantities for multimode entangled states and demonstrates its validity through experiments, advancing conditional state preparation techniques.

Findings

Model accurately predicts detection probabilities and conditional states.

Experimental results agree with theoretical predictions.

Conditional states exhibit significant non-Gaussianity depending on parameters.

Abstract

We address the intrinsic multimode nature of the quantum state of light obtained by pulsed spontaneous parametric downconversion and develop a theoretical model based only on experimentally accessible quantities. We exploit the pairwise entanglement as a resource for conditional multimode measurements and derive closed formulas for the detection probability and the density matrix of the conditional states. We present a set of experiments performed to validate our model in different conditions that are in excellent agreement with experimental data. Finally, we evaluate nonGaussianity of the conditional states obtained from our source with the aim of discussing the effects of the different experimental parameters on the efficacy of this type of conditional state preparation.