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Entanglement Witness for NMR Quantum Information Processing

Robabeh Rahimi, Takeda, K, Masanao Ozawa, Kitagawa, M

Published Jan 1, 2004• 0 citations
OpenAlex

Abstract

We discuss the tricky issue of entanglement in NMR quantum information processing and particularly NMR implementation of superdense coding. The signal intensity is introduced as a critical experimental property and an experimental approach for detection of entanglement is proposed based on the signal intesity measurements in a single NMR experiment.

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We discuss the tricky issue of entanglement in NMR quantum information processing and particularly NMR implementation of superdense coding. The signal intensity is introduced as a critical experimental property and an experimental approach for detection of entanglement is proposed based on the signal intesity measurements in a single NMR experiment.
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In this study, we report an experiment realization of quantum superdense coding (QSDC) between three parties using nuclear magnetic resonance (NMR). The experimental results have shown that in terms of the QSDC schemes between multiparties proposed by Liu et al. and Crudka et al., three-qubit QSDC can transmit three bits of classical information by sending two qubits only. Our results experimentally show that quantum superdense coding, as one of the quantum information processing protocols, is superior to classical ones.
Quantum dense coding has been demonstrated experimentally in terms of quantum logic gates and circuits in quantum computation and NMR technique. Two bits of information have been transmitted through manipulating one of the maximally entangled two-state quantum pairs, which is completely consistent with the original ideal of the Bennett-Wiesner proposal. Although information transmission happens between spins over interatomic distance, the scheme of entanglement transformation and measurement can be used in other processes of quantum information and quantum computing.
Random local measurements have recently been proposed to construct entanglement witnesses and thereby detect the presence of bipartite entanglement. We experimentally demonstrate the efficacy of one such scheme on a two-qubit NMR quantum-information processor. We show that a set of three random local measurements suffices to detect the entanglement of a general two-qubit state. We experimentally generate states with different amounts of entanglement and show that the scheme is able to clearly witness entanglement. We perform complete quantum state tomography for each state and compute state fidelity to validate our results. Further, we extend previous results and perform a simulation using random local measurements to optimally detect bipartite entanglement in a hybrid system of $2\ensuremath{\bigotimes}3$ dimensionality.