Entanglement Witnesses of Condensation for Enhanced Quantum Sensing

TL;DR

This paper demonstrates that collective entanglement from particle-hole pair condensation in spin qubits can significantly amplify transition amplitudes, enhancing quantum sensing capabilities through a robust, entanglement-based mechanism.

Contribution

It introduces a novel entanglement witness based on particle-hole condensation that can be used to design more sensitive quantum sensors.

Findings

Achieves an $ ext{O}(\sqrt{N})$ enhancement of transition amplitudes.

Shows robustness of the effect to noise.

Identifies optimal geometries for maximum condensation and amplification.

Abstract

Quantum phenomena such as entanglement provide powerful resources for enhancing classical sensing. Here, we theoretically show that collective entanglement of spin qubits, arising from a condensation of particle-hole pairs, can strongly amplify transitions between ground and excited spin states, potentially improving signal contrast in optically detected magnetic resonance. This collective state exhibits an $\mathcal{O}(\sqrt{N})$ enhancement of the transition amplitude with respect to an applied microwave field, where $N$ is the number of entangled spin qubits. We computationally realize this amplification using an ensemble of $N$ triplet spins with magnetic dipole interactions, where the largest transition amplitudes occur at geometries for which the condensation of particle-hole pairs is strongest. This effect, robust to noise, originates from the concentration of entanglement into a single collective mode, reflected in a large eigenvalue of the particle-hole reduced density matrix -- an entanglement witness of condensation analogous to off-diagonal long-range order, though realized here in a finite system. These results offer a design principle for quantum sensors that exploit condensation-inspired entanglement to boost sensitivity in spin-based platforms.