Collective three-body interactions enable a robust quantum speedup

TL;DR

This paper demonstrates that collective three-body interactions in optical cavities significantly enhance the speed and sensitivity of quantum state preparation and phase estimation, outperforming traditional two-body methods especially in large ensembles.

Contribution

It introduces a novel use of collective three-body interactions for faster entanglement generation and improved quantum metrology, surpassing existing two-body interaction techniques.

Findings

Achieves a speedup of order N in preparing GHZ states.

Saturates the Heisenberg limit in phase estimation.

Maintains high sensitivity and fast entanglement generation despite decoherence.

Abstract

We show that collective three-body interactions (3BIs), implementable with $N$ atoms loaded inside an optical cavity, offer a significant advantage for preparing complex multipartite entangled states. Firstly, they enable a speedup of order $\sim N$ in preparing generalized Greenberger-Horne-Zeilinger (GHZ) states, outperforming conventional methods based on all-to-all two-body Ising interactions. Secondly, they saturate the Heisenberg bound in phase estimation tasks using a time-reversal protocol realized through simple rotations and followed by experimentally accessible collective spin measurements. Lastly, compared with two-body interactions (2BIs), in the presence of cavity losses and single particle decoherence, 3BIs feature a high gain in sensitivity for moderate atom numbers and in large ensembles a fast entanglement generation despite constraints in parameter regimes where they are implementable.