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Conference on Lasers and Electro-Optics

Using Hyperentangled Photons to Prepare Bound Entanglement

Aditya N. Sharma, Julio T. Barreiro, Paul G. Kwiat

Published Jan 1, 2010• 0 citations
Publisher

Abstract

We present an experimental setup to prepare the bound-entangled Smolin state using hyperentangled photons produced by spontaneous parametric down-conversion. We can verify the state produced using quantum state tomography and “unlocking” of entanglement.
DOI
10.1364/qels.2010.qthj4

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Quantum entanglement exhibits various interesting features that emerge only in high-dimensional systems. One of the most fascinating is bound entanglement, entanglement that cannot be extracted using local operations and classical communication. This thesis describes our work towards an experimental realization of the four-qubit bound-entangled Smolin state, using the polarization and spatial mode of photon pairs. We describe a number of interesting experimental challenges that this work faced. We present our results on entangled two-qubit spatial mode states and hyperentangled four-qubit polarization-spatial-mode states generated by spontaneous parametric down-conversion from a second-order TEM mode pump. Some of the subtleties involved in preparing genuine mixed states in the lab are discussed.
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We experimentally demonstrate the first quantum system entangled in every degree of freedom (hyperentangled). Using pairs of photons produced in spontaneous parametric down-conversion, we verify entanglement by observing a Bell-type inequality violation in each degree of freedom: polarization, spatial mode, and time energy. We also produce and characterize maximally hyperentangled states and novel states simultaneously exhibiting both quantum and classical correlations. Finally, we report the tomography of a 2 x 2 x 3 x 3 system (36-dimensional Hilbert space), which we believe is the first reported photonic entangled system of this size to be so characterized.
Quantum entanglement is known to enable otherwise impossible feats in various communication protocols, such as quantum key distribution and super-dense coding. Here we describe efforts to further enhance the usual benefits, by incorporating quantum states that are simultaneously entangled in multiple degrees of freedom – “hyperentangled”. Via the process of spontaneous parametric down conversion, we have demonstrated photon pairs simultaneously entangled in polarization and spatial mode, and have used these to realize remote entangled state preparation, full polarization Bell-state analysis, and the highest reported capacity quantum dense coding.