Channel Capacity Gain in Entanglement-Assisted Communication Protocols Based Exclusevly on Linear Optics and Single Photon Inputs

Abstract

Entanglement can effectively increase communication channel capacity as evidenced by dense coding that predicts a capacity gain of 1 bit when compared to entanglement-free protocols. However, dense coding relies on Bell states and when implemented using photons the capacity gain is bounded by $0.585$ bits due to one's inability to discriminate between the four optically encoded Bell states. In this paper we study the following question: Are there alternative entanglement-assisted protocols that rely only on linear optics, coincidence photon counting and separable single photon input states and at the same time provide a greater capacity gain than $0.585$ bits. We show that besides the Bell states there is a class of bipartite four-mode two-photon entangled states that facilitate an increase in channel capacity. We also discuss how the proposed scheme can be generalized to the case of two-photon $N$-mode entangled states for $N=6,8$.

resubmitted version, improved presentation, added discussion

References in corpus (4)

• Detecting Single Infrared Photons with 93% System Efficiency
• Beating the channel capacity limit for linear photonic superdense coding
• Complete and Deterministic discrimination of polarization Bell state assisted by momentum entanglement
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Cited by in corpus (3)

• Superdense coding over optical fiber links with complete Bell-state measurements
• Optimal entangling operations between deterministic blocks of qubits encoded into single photons
• Optimal Encoding Capacity of a Linear Optical Quantum Channel