Suppressing correlated noise in signals transmitted over the Gaussian   memory channels using $2N$-port splitter and phase flips
  A scheme for suppressing the correlated noise in signals transmitted over the bosonic Gaussian memory channels is proposed. This is a compromise solution rather than removing the noise completely. The scheme is based on linear optical elements, two $N$-port splitters and $N$ number of phase flips. The proposed scheme has the advantages that the correlated noise of the memory channels are greatly suppressed, and the input signal states can be protected excellently when transmitting over the noise channels. We examine the suppressing efficiency of the scheme for the correlated noise, both from quantum information of the states directly transmitted through the noise channel and also from the entanglement teleportation. The phase flips are very important aspects for the suppressions of the correlated noise, which transform the roles of the memory factor from completely negative to positive in quantum information communications. Increasing the number of beam splitters also can improve the suppressing efficiency of the scheme in communications. 
Ke-Xia Jiang, Shi-Quan Zhang, San-Min Ke, and Heng Fan
quant-ph