Optical Experiments on Shared Quantum Correlations

Abstract

Shared quantum correlations find application in a wide range of modern quantum information protocols. This thesis presents several optical experiments towards the improved certification of shared quantum correlations, using photonic qubits. The first experiment demonstrates the Einstein–Podolsky–Rosen (EPR) steering effect with no detection loophole. Polarisation–entangled photon pairs generated in a Sagnac interferometer were used to test new loss–tolerant EPR steering inequalities. To test the robustness of the loss–tolerant EPR steering nequalities, a transmission loss of −4.3dB was introduced using a 1km optical fibre loop, finding inequality violations for n = 10 and n = 16 measurement settings with no detection loophole (equating to a total loss of 87%). The findings demonstrate how the new loss–tolerant protocols can be used to certify the EPR steering effect for arbitrarily high losses, and may find application in one–sided device–independent quantum key distribution protocols. The second experiment introduces EPR steering in the context of an EPR steering game. The rules of the game allow for certification of shared quantum correlations via EPR steering inequalites without requiring trust in devices or parties external to a quantum referee. In particular, the experiment successfully demonstrates EPR steering in a measurement–device independent framework; a framework which has typically been accessible only through Bell inequality violations. The findings suggest the possibility for quantum–refereed one–sided device–independent quantum key distribution protocols.