Analia Zwick, Gonzalo A. Álvarez, Joachim Stolze, Omar Osenda
The transmission of quantum states through spin chains is an important task in the implementation of quantum information technologies. Many protocols were developed to achieve the high fidelities needed for the state transfer. However, highly demanding and challenging requirements have to be met that are not feasible with present technologies. The main difficulty is the finite precision of the engineering of quantum devices. Very recently, conditions have been identified which enable reliable and robust transmission in the presence of exchange coupling disorder. These conditions only require control of the boundary couplings of the channel rather than the very demanding engineering of the complete set of couplings. In this work we present a systematic study of the principal disordered spin chains that have been analyzed in the literature as possible quantum information transmission channels. Our study focuses on the properties of the chain configuration which ensure, on average, a successful state transmission, but not on the encoding of the state to be transmitted or on means to improve the readout of the arriving signal. We demonstrate that quite different XX spin chain configurations subjected to the same disorder model show qualitatively the same performance. More importantly, that performance, as measured by the fidelity, shows the same scaling behavior with chain length and disorder strength for all systems studied. Our results are helpful in identifying the optimal spin chain for a given quantum information transfer task. In particular, they help in judging whether it is worthwhile to engineer all couplings in the chain as compared to adjusting only the boundary couplings.
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http://arxiv.org/abs/1306.1695
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