Entanglement-assisted tomography of a quantum target

TL;DR

This paper investigates how entanglement-assisted strategies improve the efficiency of quantum state tomography of a qubit via scattering, highlighting the role of quantum correlations in estimation accuracy.

Contribution

It provides a comparative analysis of entanglement-assisted and non-assisted quantum tomography using scattering, emphasizing the significance of quantum correlations.

Findings

Entanglement-assisted strategies improve estimation accuracy over non-assisted methods.

Quantum correlations significantly enhance the efficiency of quantum tomography.

Direct estimation of the quantum target yields higher accuracy than probe-based methods.

Abstract

We study the efficiency of quantum tomographic reconstruction where the system under investigation (quantum target) is indirectly monitored by looking at the state of a quantum probe that has been scattered off the target. In particular we focus on the state tomography of a qubit through a one-dimensional scattering of a probe qubit, with a Heisenberg-type interaction. Via direct evaluation of the associated quantum Cram\'{e}r-Rao bounds, we compare the accuracy efficiency that one can get by adopting entanglement-assisted strategies with that achievable when entanglement resources are not available. Even though sub-shot noise accuracy levels are not attainable, we show that quantum correlations play a significant role in the estimation. A comparison with the accuracy levels obtainable by direct estimation (not through a probe) of the quantum target is also performed.