Quantum Correlations, Nuclearity, and Spacetime Curvature

Ivana Đorđević, Aleksandra Gočanin, Dragoljub Gočanin

Building on the framework developed by Perche [Phys. Rev. D 106, 025018 (2022)], we study two localized nonrelativistic quantum particles propagating along timelike geodesics in a curved spacetime background. Each particle is coupled to a quantum clock that operationally records the time spent in a prescribed spatial region. We compute the covariance of the resulting time observables for separable and entangled two-particle states, comparing flat and curved backgrounds. We then reformulate the protocol as a Bell-like experiment and show that the Bell parameter can acquire a curvature-induced correction. In particular, a protocol calibrated to saturate the classical bound in flat spacetime can be driven above this bound in curved spacetime for entangled states. We focus on two-dimensional curved backgrounds in which the local tidal term induces an effective harmonic potential in the Fermi-frame description. Our results show that spacetime curvature can modify operationally defined quantum correlations and suggest entangled quantum clocks as probes of spacetime curvature.

Elihu Lubkin

Mohamed Amazioug, Mohammed Daoud A

We study the distribution of bipartite and tripartite quantum entanglement across causally disconnected regions (open charts) in de Sitter spacetime. We first consider a two-mode squeezed state shared between Alice and Bob, where the Gaussian channel models the effects of spacetime curvature. We employ Gaussian Rényi-2 entanglement as a witness for quantum entanglement, while Gaussian geometric discord is a measure of quantumness beyond entanglement, including entanglement. The Gaussian Rényi-2 classical correlations are used to quantify the correlations. Besides, we achieve tripartite entanglement among the open chart modes, quantified by residual Gaussian Rényi-2 entanglement. Our results demonstrate the generation of bipartite entanglement between spatially separated observers due to strong curvature. The impact of curvature on both classical and quantum correlations is shown to be particularly pronounced for conformal and massless scalar fields. Hence, residual Gaussian Rényi-2 entanglement is generated among the open chart modes due to the influence of de Sitter curvature for all nonzero squeezing values.

Marek Kuś

Vesselin Petkov

He Wang, Jin Wang

Abstract We investigate the equilibrium and nonequilibrium quantum information correlations encoded in a two-qubit system in curved spacetime near the horizon of a Kerr black hole. We study the impact of mass and the angular momentum and further the local curvature or accelerations on the behaviors of the quantum correlations between the two qubits. We show that the quantum information of the two qubits is encoded in the spacetime structure. Concretely, the quantum correlations in the two-qubit system vary non-monotonically with the mass of the black hole and are amplified by the angular momentum, while the curvature suppresses the quantum correlations in the system. We show that the nonequilibrium can also contribute to the quantum correlations. Remarkably, the nonequilibrium can lead to the increase of quantum correlations in the steady state under the curved spacetime shown in this black hole example.