Entangled sensor-networks for dark-matter searches

TL;DR

This paper develops a theoretical framework for using entangled sensor networks with quantum squeezing to enhance dark matter axion searches, combining signals coherently and reducing noise via multipartite entanglement.

Contribution

It introduces a novel approach to leverage quantum entanglement and squeezing across multiple sensors for improved axion detection in dark matter research.

Findings

Entangled sensor networks can coherently combine signals for better sensitivity.

Multipartite entanglement reduces noise across the sensor network.

GKP states offer limited practical advantage over squeezed states in this context.

Abstract

The hypothetical axion particle (of unknown mass) is a leading candidate for dark matter (DM). Many experiments search for axions with microwave cavities, where an axion may convert into a cavity photon, leading to a feeble excess in the output power of the cavity. Recent work [Nature 590, 238 (2021)] has demonstrated that injecting squeezed vacuum into the cavity can substantially accelerate the axion search. Here, we go beyond and provide a theoretical framework to leverage the benefits of quantum squeezing in a network setting consisting of many sensor-cavities. By forming a local sensor network, the signals among the cavities can be combined coherently to boost the axion search. Furthermore, injecting multipartite entanglement across the cavities -- generated by splitting a squeezed vacuum -- enables a global noise reduction. We explore the performance advantage of such a local, entangled sensor-network, which enjoys both coherence between the axion signals and entanglement between the sensors. Our analyses are pertinent to next-generation DM-axion searches aiming to leverage a network of sensors and quantum resources in an optimal way. Finally, we assess the possibility of using a more exotic quantum state, the Gottesman-Kitaev-Preskill (GKP) state. Despite a constant-factor improvement in the scan-time relative to a single-mode squeezed-state in the ideal case, the advantage of employing a GKP state disappears when a practical measurement scheme is considered.