Practical scheme for noiseless filtering of continuous variable information with non-Gaussian noise

Every practical quantum channel degrades the quality of quantum states transmitted between two parties. In order to establish a communication with a low error rate, it is therefore important to determine and, if possible, to decrease the influence of noise in the quantum channel. We investigate an optical quantum channel with non-Gaussian noise characteristics, which transforms a signal state into a statistical mixture of signal and vacuum. We propose and experimentally demonstrate a new scheme for a noiseless and optimal quantum filter or quantum relay filtering vacuum states from this mixture. Two different filters were implemented; one which is relying on weak homodyne measurements and one on weak on/off measurements. The performance of the two schemes is compared relative to the optimal scheme