Parity-time-symmetric two-qubit system: entanglement and sensing

TL;DR

This paper investigates exceptional-point effects and quantum sensing in a PT-symmetric two-qubit system, revealing enhanced entanglement dynamics and sensitivity at EPs, with potential applications in quantum measurement.

Contribution

It introduces a detailed analysis of EP effects and entanglement behavior in a PT-symmetric two-qubit system, highlighting enhanced sensing capabilities at EPs.

Findings

Steady-state entanglement can be generated in the PT-broken phase.

Collapse-revival of entanglement occurs in the PT-symmetric phase.

Eigenstate sensitivity is significantly enhanced at EPs.

Abstract

In this paper we study exceptional-point (EP) effects and quantum sensing in a parity-time (PT)-symmetric two-qubit system with the Ising-type interaction. We explore EP properties of the system by analyzing degeneracy of energy eigenvalues or entanglement of eigenstates. We investigate entanglement dynamics of the two qubits in detail. In particular, we demonstrate that the system can create the steady-state entanglement in the PT-broken phase and collapse-revival phenomenon of entanglement in the PT-symmetric phase during the long-time evolution. We show that entanglement can be generated more quickly than the corresponding Hermitian system. Finally, we prove that the sensitivity of eigenstate quantum sensing for the parameters exhibits the remarkable enharncement at EPs, and propose a quantum-coherence measurement to witness the existence of EPs.