Quantum repeaters based on CNOT gate under decoherence |
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Authors: | Tong Zhao-yang Liao Ping and Kuang Le-man |
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Institution: | (1) Key Laboratory of Quantum Structures and Quantum Control of Ministry of Education, and Department of Physics, Hunan Normal University, Changsha, 410081, China |
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Abstract: | In this paper, we study single-qubit and single-user quantum repeaters based on CNOT gates under decoherence using the Kraus-operator
representations of decoherence. We investigate the influence of decoherence on the information-disturbance trade-off of quantum
repeaters. It is found that decoherence may lead to the appearance of three subspaces, called as the normal subspace, the
anomalous subspace, and the decoherence-free subspace (DFS), respectively. It is indicated that in the normal subspace decoherence
decreases the transmission and estimation fidelities, in the anomalous subspace decoherence enhances these fidelities, and
in the DFS these fidelities do not change. The concept of the quality factor is introduced to evaluate the quality of the
quantum repeater. It is indicated that the quality factor can be efficiently controlled and manipulated by changing the initial
state of the probe qubit. It is found that under certain conditions the quantum repeater can be optimal even in the presence
of decoherence.
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Keywords: | quantum repeaters quantum decoherence quality factor information-disturbance tradeoff Kraus operators |
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