The effect of channel decoherence on entangled coherent states: A theoretical analysis

TL;DR

This paper theoretically analyzes how channel losses affect entangled coherent states compared to Bell states, revealing that ECSs with small amplitudes are more robust against decoherence.

Contribution

It provides explicit formulas for entanglement degradation of ECSs under asymmetric and symmetric noise, highlighting their robustness over biphoton states.

Findings

Small amplitude ECSs are more resilient to decoherence.

Explicit expressions for entanglement measures are derived.

Results differ from previous studies in the small amplitude limit.

Abstract

We analyse decoherence properties of entangled coherent states (ECSs) due to channel losses, and compare to the performance of bi-photon Bell states. By employing the concept of "entanglement of formation" (EOF), the degradation of fidelity and degree of entanglement are calculated. Two situations are considered: (1) asymmetric and (2) symmetric noise channel. In the first case, only the lower bound of EOF is given. However, in the latter case, we have obtained an explicit expression of concurrence (and then EOF) and found surprisingly our result is just incompatible with that of [Phys. Rev. A \textbf{82}, (2010) 062325] in the limit of $\alpha\rightarrow0$. We demonstrate that entangled coherent states with sufficient small amplitudes are more robust against channel decoherence than biphoton entangled states in both cases.