Observation of entanglement witnesses for orbital angular momentum states

M. Agnew, J. Leach, R.W. Boyd
2012 European Physical Journal D : Atomic, Molecular and Optical Physics  
Entanglement witnesses provide an efficient means of determining the level of entanglement of a system using the minimum number of measurements. Here we demonstrate the observation of twodimensional entanglement witnesses in the high-dimensional basis of orbital angular momentum (OAM). In this case, the number of potentially entangled subspaces scales as d(d − 1)/2, where d is the dimension of the space. The choice of OAM as a basis is relevant as each subspace is not necessarily maximally
more » ... gled, thus providing the necessary state for certain tests of nonlocality. The expectation value of the witness gives an estimate of the state of each two-dimensional subspace belonging to the d-dimensional Hilbert space. These measurements demonstrate the degree of entanglement and therefore the suitability of the resulting subspaces for quantum information applications.
doi:10.1140/epjd/e2012-30057-9 fatcat:2bi2ynxserbvplenh6xxb5eea4