| Time：115/9/16 (Wed.) 14:20~16:20 Speaker：Prof.古煥宇(Huan-Yu Ku) 國立臺灣師範大學物理學系/Department of Physics, National Taiwan Normal University Title：Perfect error filtration for all quantum channels via coherent control Abstract： A central problem in quantum communication and computation is the reduction of noise affecting quantum channels. A possible error mitigation strategy involves coherent control of quantum channels, namely, the possibility of applying different channels in a superposition. More precisely, channels acting on a particle’s internal degree of freedom, are controlled by the particle’s path degree of freedom, which can be in a coherent superposition. We show that for any noisy quantum channel, there always exists a coherent control procedure that allows one to filter, i.e., probabilistically obtain, a noiseless channel, i.e., unitary. Such a perfect error filtration is achieved in the limit of the coherent control of infinitely many copies of the channel, possibly and rather counterintuitively, after the injection of additional noise. We estimate the optimal probability and we show that the required number of copies to achieve an error $\epsilon$ scales as $N=O(1/\epsilon)$, and that the optimal noise injection is efficiently computable. Finally, we demonstrate that the principle of the perfect error filtration can be applied also on the circuit model, providing a concrete implementation in quantum information. Place：S101, Gongguan Campus, NTNU |
