The capacity of quantum channels with side information at the transmitter

Igor Devetak, Peter W. Shor

Frédéric Dupuis

We consider the problem of coding for quantum channels with side information that is available ahead of time at the transmitter but not at the receiver. We find a single-letter expression for the entanglement-assisted quantum capacity of such channels which closely parallels Gel'fand and Pinsker's solution to the classical version of the same problem.

Bin Dai, Yuan Luo

In this paper, the model of wiretap channel has been reconsidered for the case that the main channel is controlled by channel state information (side information), and it is available at the transmitter in a noncausal manner (termed here noncausal side information) or causal manner (termed here causal side information). Inner and outer bounds are derived on the capacity-equivocation regions for the noncausal and causal manners, and the secrecy capacities for both manners are described and bounded, which provide the best transmission rate with perfect secrecy. Moreover, for the case that the side information is available at the transmitter in a memoryless manner (termed here memoryless side information), both the capacity-equivocation region and the secrecy capacity are determined. The results of this paper extend the previous work on wiretap channel with noncausal side information by providing an outer bound on the capacity-equivocation region. In addition, we find that the memoryless side information can not help to obtain the same secrecy capacity as that of the causal case, and this is different from the well known fact that the memoryless manner can achieve the capacity of the channel with causal side information.

Rex A. C. Medeiros, Francisco de Assis

Elloá B. Guedes, Francisco de Assis, Rex A. C. Medeiros

Uzi Pereg

Entanglement-assisted communication over a random-parameter quantum channel with either causal or non-causal channel side information (CSI) at the encoder is considered.This describes a scenario where the quantum channel depends on the quantum state of the input environment.While Bob, the decoder, has no access to this state, Alice, the transmitter, performs a sequence of projective measurements on her environment to encode her message.Dupuis [10,9] established the entanglement-assisted capacity with non-causal CSI.Here, we establish characterization in the causal setting, and also give an alternative proof technique and further observations for the non-causal setting.