Polarization-Entanglement Dynamics in Optical Fibers: Mitigating Decay in the Non-Markovian Regime with Dynamical Decoupling

TL;DR

This paper models polarization-entanglement decay in optical fibers due to refractive index fluctuations and demonstrates that dynamical decoupling with half waveplates can significantly mitigate entanglement loss in non-Markovian regimes.

Contribution

It introduces a detailed spin-boson model for entanglement decay in optical fibers and proposes dynamical decoupling schemes to counteract this decay.

Findings

Entanglement decay exhibits both Markovian and non-Markovian behavior.

Dynamical decoupling with spaced half waveplates reduces entanglement loss.

Uhrig and Carr-Purcell-Meiboom-Gill schemes improve entanglement preservation.

Abstract

Future distributed quantum systems and networks are likely to rely, at least in part, on the existing fiber infrastructure for entanglement distribution; hence, a precise understanding of the adverse effects of imperfections in optical fibers on entanglement is essential to their operation. Here, we consider maximally entangled polarization qubits and study the decay of the entanglement caused by spatial fluctuations in the refractive index of optical fibers. We study this entanglement dynamics using the spin-boson model and numerically solve our system of equations using the hierarchical equations of motion (HEOM) formalism. We show that within the range of practically relevant system parameters, our developed model exhibits both Markovian and non-Markovian entanglement decay behavior. Further, to counter the observed entanglement decay, we propose the implementation of dynamical decoupling in optical fibers using spaced half waveplates. In particular, we numerically model the time-dependent Hamiltonians of the Carr-Purcell-Meiboom-Gill and Uhrig dynamical decoupling schemes and show a reduced rate of entanglement decay even with sparsely spaced half waveplates along the length of optical fiber. Finally, we evaluate the performance of these two schemes in multiple system configurations.