Entanglement Dynamics in the Presence of Controlled Unital Noise

TL;DR

This paper investigates how entanglement between qubits degrades under unital noise, providing theoretical formulas and experimental validation for entanglement dynamics in various noise scenarios.

Contribution

It derives a simple relation for entanglement decay under unital channels and experimentally verifies the dynamics for both maximally and partially entangled states.

Findings

Entanglement decay relates directly to noise representation in the Bloch sphere.

Experimental results confirm theoretical predictions for various unital channels.

Different evolution observed for mixed and pure initial states with same entanglement.

Abstract

Quantum entanglement is notorious for being a very fragile resource. Significant efforts have been put into the study of entanglement degradation in the presence of a realistic noisy environment. Here, we present a theoretical and an experimental study of the decoherence properties of entangled pairs of qubits. The entanglement dynamics of maximally entangled qubit pairs is shown to be related in a simple way to the noise representation in the Bloch sphere picture. We derive the entanglement level in the case when both qubits are transmitted through any arbitrary unital Pauli channel, and compared it to the case when the channel is applied only to one of the qubits. The dynamics of both cases was verified experimentally using an all-optical setup. We further investigated the evolution of partially entangled initial states. Different dynamics was observed for initial mixed and pure states of the same entanglement level.