Distributed quantum sensing with a mode-entangled network of spin-squeezed atomic states

TL;DR

This paper demonstrates that nonlocal entanglement in a distributed quantum sensor network enhances measurement precision beyond classical limits, using a shared quantum nondemolition measurement across up to four nodes.

Contribution

It introduces a method to entangle multiple sensor nodes via quantum nondemolition measurement, achieving improved scaling and precision in a distributed quantum sensing network.

Findings

Up to 4.5 dB better precision with nonlocal entanglement

11.6 dB improvement over quantum projection noise limit

Applicable to atomic clock and interferometer protocols

Abstract

Quantum sensors are used for precision timekeeping, field sensing, and quantum communication. Comparisons among a distributed network of these sensors are capable of, for example, synchronizing clocks at different locations. The performance of a sensor network is limited by technical challenges as well as the inherent noise associated with the quantum states used to realize the network. For networks with only local entanglement at each node, the noise performance of the network improves at best with square root of the number of nodes. Here, we demonstrate that nonlocal entanglement between network nodes offers better scaling with network size. A shared quantum nondemolition measurement entangles a clock network with up to four nodes. This network provides up to 4.5 dB better precision than one without nonlocal entanglement, and 11.6 dB improvement as compared to a network of sensors operating at the quantum projection noise limit. We demonstrate the generality of the approach with atomic clock and atomic interferometer protocols, in scientific and technologically relevant configurations optimized for intrinsically differential comparisons of sensor outputs.