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arXiv · 1703.01965

Proposed optical realisation of a two photon, four-qubit entangled $χ$ state

Atirach Ritboon·Sarah Croke·Stephen M. Barnett
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Abstract

The four-qubit states $\lvertχ^{ij}\rangle$, exhibiting genuinely multi-partite entanglement have been shown to have many interesting properties and have been suggested for novel applications in quantum information processing. In this work we propose a simple quantum circuit and its corresponding optical embodiment with which to prepare photon pairs in the $\lvertχ^{ij}\rangle$ states. Our approach uses hyper-entangled photon pairs, produced by the type-I spontaneous parametric down-conversion (SPDC) process in two contiguous nonlinear crystals, together with a set of simple linear-optical transformations. Our photon pairs are maximally hyper-entangled in both their polarisation and orbital angular momentum (OAM). After one of these daughter photons passes through our optical setup, we obtain photon pairs in the hyper-entangled state $\lvertχ^{00}\rangle$, and the $\lvertχ^{ij}\rangle$ states can be achieved by further simple transformations.

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Atirach Ritboon, Sarah Croke, Stephen M. Barnett. 2017-03-06. Proposed optical realisation of a two photon, four-qubit entangled $χ$ state. https://doi.org/10.1088/2040-8986%2Faa72af

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