Multiqubit entanglement of a general input state
Behrman, Elizabeth C.
Steck, James E.
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Behrman, Elizabeth C.; Steck, James E. 2013. Multiqubit entanglement of a general input state. Quantum Information & Computation, v.13 no.1-2 pp.36-53
Measurement of entanglement remains an important problem for quantum information. We present the design and simulation of an experimental method for an entanglement indicator for a general multiqubit state. The system can be in a pure or a mixed state, and it need not be "close" to any particular state. The system contains information about its own entanglement; we use dynamic learning methods to map this information onto a single experimental measurement which is our entanglement indicator. Our method does not require prior state reconstruction or lengthy optimization. An entanglement witness emerges from the learning process, beginning with two-qubit systems, and extrapolating this to three, four, and five qubit systems where the entanglement is not well understood. Our independently learned measures for three-qubit systems compare favorably with known entanglement measures. As the size of the system grows the amount of additional training necessary diminishes, raising hopes for applicability to large computational systems.
The article is available for purchase at the publisher's website: http://www.rintonpress.com/journals/qiconline.html#v13n12