Enhancing precision of damping rate by PT symmetric Hamiltonian

TL;DR

This paper explores how PT symmetric Hamiltonians can enhance the precision of damping rate measurements in dissipative qubits, demonstrating improved accuracy and the role of entanglement near exceptional points.

Contribution

It introduces two models using PT symmetric Hamiltonians to improve damping rate precision, highlighting the benefits over traditional methods and the impact of entanglement.

Findings

Direct PT symmetric feedback yields better damping rate precision.

Uncertainty approaches zero at the exceptional point.

Non-maximal entanglement can reach Heisenberg limit.

Abstract

We utilize quantum Fisher information to investigate the damping parameter precision of a dissipative qubit. PT symmetric non-Hermitian Hamiltonian is used to enhance the parameter precision in two models: one is direct PT symmetric quantum feedback; the other is that the damping rate is encoded into a effective PT symmetric non-Hermitian Hamiltonian conditioned on the absence of decay events. We find that compared with the case without feedback and with Hermitian quantum feedback, direct PT symmetric non-Hermitan quantum feedback can obtain better precision of damping rate. And in the second model the result shows that the uncertainty of damping rate can be close to 0 at the exceptional point. We also obtain that non-maximal multiparticle entanglement can improve the precision to reach Heisenberg limit.