Quantum Metrology Protected by Hilbert Space Fragmentation

TL;DR

This paper introduces a quantum sensing method leveraging Hilbert-space fragmentation to achieve Heisenberg-limited sensitivity that is robust against inhomogeneous Ising interactions, avoiding thermalization effects.

Contribution

It demonstrates how to use Hilbert-space fragmentation to create stable, decoupled spin states for enhanced quantum metrology under realistic interactions.

Findings

Achieves Heisenberg-limited sensitivity in a many-body system.

Shows robustness of the sensing scheme against inhomogeneous interactions.

Provides analytical proof of stable decoupled states via HSF.

Abstract

We propose an entanglement-enhanced sensing scheme that is robust against spatially inhomogeneous always-on Ising interactions. Our strategy is to tailor coherent quantum dynamics employing the Hilbert-space fragmentation (HSF), a recently recognized mechanism that evades thermalization in kinetically constrained many-body systems. Specifically, we analytically show that the emergent HSF caused by strong Ising interactions enables us to design a stable state where part of the spins is effectively decoupled from the rest of the system. Using the decoupled spins as a probe to measure a transverse field, we demonstrate that the Heisenberg limited sensitivity is achieved without suffering from thermalization.