Extracting an entanglement signature from only classical mutual information

Andrew G. White, Daniel F. V. James, William J. Munro +1 more

David J. Starling, John C. Howell

We use classical mutual information to characterize two photons measured in three mutually unbiased bases. We theoretically and experimentally compare entangled and separable states and find a bound on the information capacity of the pair.

David J. Starling, Curtis J. Broadbent, John C. Howell

We introduce a quantity which is formed using classical notions of mutual information and which is computed using the results of projective measurements. This quantity constitutes a sufficient condition for entanglement and represents the amount of information that can be extracted from a bipartite system for spacelike separated observers. In addition to discussion, we provide simulations as well as experimental results for the singlet and maximally correlated mixed states.

Zeilinger

Yu Tang, Wentao Liu, Zhilong Liu +1 more

A bstract In this paper, we explore correlation harvesting in quantum superposition, specifically focusing on the entanglement and mutual information extracted by two Unruh-DeWitt detectors interacting with a quantum field in a mass-superposed BTZ black hole spacetime. Our findings reveal that the superposed nature of spacetime induces constructive interference between the field modes that can significantly enhance the entanglement harvesting relative to a single spacetime background. In contrast to entanglement, the mutual information obtained in spacetime superposition is influenced by the proper distance between the two detectors. While the mutual information harvested in a superposed spacetime remains lower than that in a single spacetime when the proper distance between detectors is small, it exceeds that in a single spacetime for specific mass ratios as the distance increases. Notably, we find that both entanglement and mutual information harvesting reach their maxima when the final spacetime superposition state is conditioned to align with the initial spacetime state.