# Enhanced Multi-Qubit Phase Estimation in Noisy Environments by Local Encoding

## TL;DR

This paper demonstrates that local encoding of multi-qubit states enhances robustness against noise, significantly improving phase estimation accuracy in noisy environments, which is crucial for practical quantum metrology and error correction.

## Contribution

The study experimentally shows that single-qubit local encoding improves noise resilience of four-qubit graph states for phase estimation, a novel approach for noisy quantum devices.

## Key findings

- Local encoding enhances entanglement robustness against noise.
- Significant improvement in phase estimation accuracy with local encoding.
- Potential applications in quantum metrology and error correction.

## Abstract

The first generation of multi-qubit quantum technologies will consist of noisy, intermediate-scale devices for which active error correction remains out of reach. To exploit such devices, it is thus imperative to use passive error protection that meets a careful trade-off between noise protection and resource overhead. Here, we experimentally demonstrate that single-qubit encoding can significantly enhance the robustness of entanglement and coherence of four-qubit graph states against local noise with a preferred direction. In particular, we explicitly show that local encoding provides a significant practical advantage for phase estimation in noisy environments. This demonstrates the efficacy of local unitary encoding under realistic conditions, with potential applications in multi-qubit quantum technologies for metrology, multi-partite secrecy and error correction.