Decoherence-assisted detection of entanglement of two qubit states

TL;DR

This paper introduces a novel method leveraging decoherence and environmental noise to detect entanglement in two-qubit systems, using a criterion similar to CHSH inequality that is sensitive to noise correlations.

Contribution

It presents a new entanglement detection technique based on decoherence effects and environmental noise control, applicable for characterizing quantum states and environmental noise types.

Findings

The inequality detects entanglement only in non-separable states with correlated noise.

The method can distinguish Gaussian from non-Gaussian environmental noise.

Decoherence can be harnessed as a tool for entanglement detection.

Abstract

We show that the decoherence, which in the long run destroys quantum features of a system, can be used to reveal the entanglement in a two-qubit system. To this end, we consider a criterion that formally resembles the Clauser-Horne-Shimony-Holt (CHSH) inequality. In our case the local observables are set by the coupling of each qubit to the environmental noise, controlled with the dynamical decoupling method. We demonstrate that the constructed inequality is an entanglement criterion---it can only be violated by non-separable initial two-qubit states, provided that the local noises are correlated. We also show that for a given initial state, this entanglement criterion can be repurposed as a method of discriminating between Gaussian and non-Gaussian noise generated by the environment of the qubits. The latter application is important for ongoing research on using qubits to characterize the dynamics of environment that perturbs them and causes their decoherence