Entanglement enhanced metrology with quantum many-body scars

TL;DR

This paper demonstrates how quantum many-body scars can be used to generate stable multipartite entanglement for quantum metrology, achieving phase estimation precision beyond the standard quantum limit.

Contribution

It introduces a method to utilize quantum many-body scars for dynamic generation of multipartite entanglement in metrological applications.

Findings

Systems with quantum many-body scars can produce stable multipartite entanglement.

Modified Hamiltonians can generate various entangled states within the scar subspace.

Metrological precision surpasses the standard quantum limit using scar-based entanglement.

Abstract

Although entanglement is a key resource for quantum-enhanced metrology, not all entanglement is useful. For example in the process of many-body thermalisation, bipartite entanglement grows rapidly, naturally saturating to a volume law. This type of entanglement generation is ubiquitous in nature but has no known application in most quantum technologies. The generation, stabilisation and exploitation of genuine multipartite entanglement, on the other hand, is far more elusive yet highly desirable for metrological applications. Recently it has been shown that quantum many-body scars can have extensive multipartite entanglement. However the accessibility of this structure for real application has been so far unclear. In this work, we show how systems containing quantum many-body scars can be used to dynamically generate stable multipartite entanglement, and describe how to exploit this structure for phase estimation with a precision that beats the standard quantum limit. Key to this is a physically motivated modification of a Hamiltonian that generates a variety of multipartite entangled states through the dynamics in the scar subspace.