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No-relationship between impossibility of faster-than-light quantum communication and distinction of ensembles with the same density matrix

Chuan Wang·Gui Lu Long·Yang Sun
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Abstract

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: 1) even with an ideal single-atom-precision measurement, it is generally impossible to produce two ensembles with exactly the same density matrix; or 2) 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.

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Chuan Wang, Gui Lu Long, Yang Sun. 2006-04-20. No-relationship between impossibility of faster-than-light quantum communication and distinction of ensembles with the same density matrix. https://doi.org/10.1088/6102%2F44%2F4%2F622

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