Experimental detection of entanglement in multimode Gaussian states from high-order intensity correlation moments

TL;DR

This paper demonstrates an experimental method to detect entanglement in multimode Gaussian states using high-order intensity correlation moments, avoiding the need for a local oscillator.

Contribution

It introduces an experimental approach to characterize entanglement in multimode Gaussian states via high-order intensity correlation moments without requiring a coherent local oscillator.

Findings

Successfully detected entanglement in two- and three-mode Gaussian states.

Used high-order (up to sixth-order) intensity correlation moments for characterization.

Method can be extended to N-mode Gaussian states with N>3.

Abstract

Quantum universal invariants of a Gaussian state's covariance matrix, which can be derived from intensity correlation moments, have been adopted to characterize the entanglement properties of Gaussian states via the positive partial transpose criterion, also known as the Peres-Horodecki separability criterion. Such intensity correlation moments enable the extraction of information about the covariance matrix without the need for a coherent local oscillator. Here, we experimentally detect the entanglement properties of multimode Gaussian states using high-order\,(up to sixth-order) intensity correlation moments. These multimode Gaussian states are prepared via spontaneous and cascaded parametric down-conversion pumped by a high-peak-energy pulsed laser. Their intensity correlation moments are measured using a pseudo-photon-number-resolving detector constructed through spatial multiplexing of 32 threshold superconducting nanowire single photon detectors. This method is successfully demonstrated for two-mode and three-mode Gaussian states and can be extended to $N$-mode Gaussian states with $N>3$.