Abstract
Quantum entanglement is the ability of joint quantum systems to possess global properties (correlation among systems) even when subsystems have no definite individual property. Whilst the 2-dimensional (qubit) case is well-understood, currently, tools to characterise entanglement in high dimensions are limited. We experimentally demonstrate a new procedure for entanglement certification that is suitable for large systems, based entirely on information-theoretics. It scales more efficiently than Bell’s inequality and entanglement witness. The method we developed works for arbitrarily large system dimension d and employs only two local measurements of complementary properties. This procedure can also certify whether the system is maximally entangled. We illustrate the protocol for families of bipartite states of qudits with dimension up to 32 composed of polarisation-entangled photon pairs.
Highlights
As the dimension of investigated systems increases, it becomes more complicated to demonstrate their quantum effects[1,2,3]
Entanglement certification refers to the fact that one has to prove that the system is entangled
One can optimize the method to the specific entangled state that one is producing
Summary
Out-performs our method for entanglement dection for the (d = 2 case) Werner state (detects entanglement at p ≥ 0.5), this is not true for arbitrary dimensions in general Comparing this against Bell’s inequalities using the Werner state, our method using mutual information with two complementary observables (computational and σx basis), for d = 2, the threshold of log2(d) is surpassed at p ≈ 0.78. The photons are collected into polarisation maintaining fibres (PMF) and are incident on the two input faces of a PBS, which transmits H and reflects V This prepares the state 1 (HV + eiθVH) when measuring in the coincidence basis. IAB +ICD is lowest for p = 1/2 which is where such state has highest discord This unexpected property is lost when the correlation is gauged with the Pearson coefficient, as CAB +CCD = 1 for all values of p
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