Simultaneous measurement of multimode squeezing

TL;DR

This paper presents an experimental method for simultaneous measurement of multimode squeezing in multiple spatial modes using optical parametric amplification and modal decomposition, simplifying characterization of multimode quantum light.

Contribution

It introduces a novel technique for measuring multimode squeezing simultaneously, improving upon previous methods that handled one mode at a time.

Findings

Successfully measured squeezing in eight spatial modes

Achieved maximum squeezing of -5.2 dB and anti-squeezing of 8.6 dB

Demonstrated the method on high-gain parametric down-conversion

Abstract

Multimode squeezed light is an increasingly popular tool in photonic quantum technologies, including sensing, imaging, and computation. Meanwhile, the existing methods of its characterization are technically complicated, and in the best case, deal with a single mode at a time. Here, we demonstrate experimentally how the squeezing can be measured in multiple spatial modes simultaneously, using optical parametric amplification and direct detection followed by modal decomposition based on spatial intensity correlations. We apply this method to a multimode squeezed vacuum generated via high-gain parametric down-conversion. We measure the degrees of squeezing and anti-squeezing for eight strongest spatial modes, obtaining highest squeezing and anti-squeezing values of $-5.2 \pm 0.2$ dB and $8.6 \pm 0.3$ dB, respectively.