It has been claimed in the literature that impossibility of faster-than-light quantum communication has an origin of indistinguishability of ensembles with the same density matrix. We show that the two concepts are no...It has been claimed in the literature that impossibility of faster-than-light quantum communication has an origin of indistinguishability of ensembles with the same density matrix. We show that the two concepts are not related.We argue that even with an ideal single-atom-precision measurement, it is generally impossible to produce two ensembles with exactly the same density matrix; or to produce ensembles with the same density matrix, classical communication is necessary. Hence the impossibility of faster-than-light communication does not imply the indistinguishability of ensembles with the same density matrix.展开更多
Since the early work of O.M.Bilanuik and B.C.Sudarshan in 1962 and G.Feinberg in 1967, the research work on the faster-than-light (superluminal) has been performed in the world, such as in USA, Europe and China. In th...Since the early work of O.M.Bilanuik and B.C.Sudarshan in 1962 and G.Feinberg in 1967, the research work on the faster-than-light (superluminal) has been performed in the world, such as in USA, Europe and China. In this paper, the development stages of the study are presented, which include beginning stage, transitional stage and experimental stage. Based on the Einstein’s paper in 1905, the velocities greater than that of light had no possibility of existence. However, in the Einstein’s papers of 1907 it was founded that the superluminal signal speed could not be refuted absolutely. In this paper, the studies on velocities are classified. The definition of General Information Speed is suggested, which will ease the discussion. After reviewing the researches of 1962-2004, it can be concluded that the faster-than-light is a realizable scientific statement.展开更多
文摘It has been claimed in the literature that impossibility of faster-than-light quantum communication has an origin of indistinguishability of ensembles with the same density matrix. We show that the two concepts are not related.We argue that even with an ideal single-atom-precision measurement, it is generally impossible to produce two ensembles with exactly the same density matrix; or to produce ensembles with the same density matrix, classical communication is necessary. Hence the impossibility of faster-than-light communication does not imply the indistinguishability of ensembles with the same density matrix.
文摘Since the early work of O.M.Bilanuik and B.C.Sudarshan in 1962 and G.Feinberg in 1967, the research work on the faster-than-light (superluminal) has been performed in the world, such as in USA, Europe and China. In this paper, the development stages of the study are presented, which include beginning stage, transitional stage and experimental stage. Based on the Einstein’s paper in 1905, the velocities greater than that of light had no possibility of existence. However, in the Einstein’s papers of 1907 it was founded that the superluminal signal speed could not be refuted absolutely. In this paper, the studies on velocities are classified. The definition of General Information Speed is suggested, which will ease the discussion. After reviewing the researches of 1962-2004, it can be concluded that the faster-than-light is a realizable scientific statement.
