Quantum Correlations beyond Entanglement and Discord

Abstract

Dissimilar notions of quantum correlations have been established, each being motivated through particular applications in quantum information science and each competing for being recognized as the most relevant measure of quantumness. In this contribution, we experimentally realize a form of quantum correlation that exists even in the absence of entanglement and discord. We certify the presence of such quantum correlations via negativities in the regularized two-mode Glauber-Sudarshan function. Our data show compatibility with an incoherent mixture of orthonormal photon-number states, ruling out quantum coherence and other kinds of quantum resources. By construction, the quantumness of our state is robust against dephasing, thus requiring fewer experimental resources to ensure stability. In addition, we theoretically show how multimode entanglement can be activated based on the generated, nonentangled state. Therefore, we implement a robust kind of nonclassical photon-photon correlated state with useful applications in quantum information processing.

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• Tracking quantum coherence in polariton condensates with time-resolved tomography
• Generalized Entanglement Measure for Continuous Variable Systems
• Entanglement of particles versus entanglement of fields: independent quantum resources
• Pauli component erasing quantum channels
• Nonclassical correlations of radiation in relation to Bell nonlocality
• Quantum correlations in general qubit-qudit axially symmetric states
• Dynamics of quantum resources in regular and Majorana fermion systems
• Distance-based approach to quantum coherence and nonclassicality
• Latent optical nonclassicality of conditionally prepared states