[Cryptography] Quantum cryptography for book entry transaction settlement?

[Robert Hettinga]

Quantum cryptography for book entry transaction settlement?

http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2016.12.html

Multi-photon entanglement in high dimensions

	• Mehul Malik,	
	• Manuel Erhard,	
	• Marcus Huber,	
	• Mario Krenn,	
	• Robert Fickler	
	• & Anton Zeilinger

Nature Photonics (2016) doi:10.1038/nphoton.2016.12
Received 20 October 2015 Accepted 19 January 2016 Published online 29 February 2016

Forming the backbone of quantum technologies today, entanglement1, 2 has been demonstrated in physical systems as diverse as photons3, ions4 and superconducting circuits5. Although steadily pushing the boundary of the number of particles entangled, these experiments have remained in a two-dimensional space for each particle. Here we show the experimental generation of the first multi-photon entangled state where both the number of particles and dimensions are greater than two. Two photons in our state reside in a three-dimensional space, whereas the third lives in two dimensions. This asymmetric entanglement structure6 only appears in multiparticle entangled states with d > 26. Our method relies on combining two pairs of photons, high-dimensionally entangled in their orbital angular momentum7. In addition, we show how this state enables a new type of ‘layered’ quantum communication protocol. Entangled states such as these serve as a manifestation of the complex dance of correlations that can exist within quantum mechanics.