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Quantum Feedback Channels

Garry Bowen
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Abstract

In Shannon information theory the capacity of a memoryless communication channel cannot be increased by the use of feedback. In quantum information theory the no-cloning theorem means that noiseless copying and feedback of quantum information cannot be achieved. In this paper, quantum feedback is defined as the unlimited use of a noiseless quantum channel from receiver to sender. Given such quantum feedback, it is shown to provide no increase in the entanglement--assisted capacities of a memoryless quantum channel, in direct analogy to the classical case. It is also shown that in various cases of non-assisted capacities, feedback may increase the capacity of memoryless quantum channels.

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Garry Bowen. 2002-09-11. Quantum Feedback Channels. https://doi.org/10.1109/tit.2004.834749

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