Loschmidt Echo for quantum metrology

TL;DR

This paper introduces a Loschmidt echo protocol that detects multiparticle entanglement and measures quantum Fisher information, enhancing quantum metrology especially for complex, non-Gaussian, and asymmetric states.

Contribution

The authors develop a versatile Loschmidt echo method applicable to diverse quantum states, enabling direct quantification of entanglement and quantum Fisher information in experimental systems.

Findings

Protocol is stable against detection errors.

Applicable to non-Gaussian and asymmetric states.

Enables characterization of entanglement in atomic systems.

Abstract

We propose a versatile Loschmidt echo protocol to detect and quantify multiparticle entanglement. It allows us to extract the quantum Fisher information for arbitrary pure states, and finds direct application in quantum metrology. In particular, the protocol applies to states that are generally difficult to characterize, as non-Gaussian states, and states that are not symmetric under particle exchange. We focus on atomic systems, including trapped ions, polar molecules, and Rydberg atoms, where entanglement is generated dynamically via long-range interaction, and show that the protocol is stable against experimental detection errors.