# Manipulation of entanglement sudden death in an all-optical setup

## TL;DR

This paper proposes an all-optical experimental setup to control entanglement sudden death (ESD), allowing it to be hastened, delayed, or prevented by applying local NOT operations during decoherence.

## Contribution

It introduces a novel all-optical method to manipulate ESD timing using local NOT operations, with analytical expressions and simulation results.

## Key findings

- The setup can delay or prevent ESD depending on operation timing.
- Analytical formulas relate initial state parameters to ESD control.
- Simulation confirms the effectiveness of the proposed manipulation.

## Abstract

The unavoidable and irreversible interaction between an entangled quantum system and its environment causes decoherence of the individual qubits as well as degradation of the entanglement between them. Entanglement sudden death (ESD) is the phenomenon wherein disentanglement happens in finite time even when individual qubits decohere only asymptotically in time due to noise. Prolonging the entanglement is essential for the practical realization of entanglement-based quantum information and computation protocols. For this purpose, the local NOT operation in the computational basis on one or both qubits has been proposed. Here, we formulate an all-optical experimental set-up involving such NOT operations that can hasten, delay, or completely avert ESD, all depending on when it is applied during the process of decoherence. Analytical expressions for these are derived in terms of parameters of the initial state's density matrix, whether for pure or mixed entangled states. After a discussion of the schematics of the experiment, the problem is theoretically analyzed, and simulation results of such manipulations of ESD are presented.