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arXiv · 1310.5433

Efficient entanglement operator for a multi-qubit system

Chiara Bagnasco·Yasushi Kondo·Mikio Nakahara
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Abstract

In liquid-state NMR quantum computation, a selective entanglement operator between qubits 2 and 3 of a three-qubit molecule is conventionally realized by applying a pair of short $π$-pulses to qubit 1. This method, called refocusing, is well suited for heteronuclear molecules. When the molecule is homonuclear, however, the $π$-pulses applied to qubit 1 often induce unwanted $z$-rotations on qubits 2 and 3, even if the $z$-components of qubits 2 and 3 are left unchanged. This phenomenon is known as the transient Bloch-Siegert effect, and compensation thereof is required for precise gate operation. We propose an alternative refocusing method, in which a weak square pulse is applied to qubit 1. This technique has the advantage of curbing the Bloch-Siegert effect, making it suitable for both hetero- and homonuclear molecules.

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Chiara Bagnasco, Yasushi Kondo, Mikio Nakahara. 2013-10-21. Efficient entanglement operator for a multi-qubit system. https://doi.org/10.1142/9789814425223_0014

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