Signatures of avoided energy-level crossings in entanglement indicators obtained from quantum tomograms

Abstract

Extensive theoretical and experimental investigations on multipartite systems close to an avoided energy-level crossing reveal interesting features such as the extremisation of entanglement. Conventionally, the estimation of entanglement directly from experimental observation involves either one of two approaches: Uncertainty-relation-based estimation that captures the linear correlation between relevant observables, or rigorous but error-prone quantum state reconstruction on tomograms obtained from homodyne measurements. We investigate the behaviour, close to avoided crossings, of entanglement indicators that can be calculated directly from a numerically-generated tomogram. The systems we study are two generic bipartite continuous-variable systems: a Bose-Einstein condensate trapped in a double-well potential, and a multi-level atom interacting with a radiation field. We also consider a multipartite hybrid quantum system of superconducting qubits interacting with microwave photons. We carry out a quantitative comparison of the indicators with a standard measure of entanglement, the subsystem von Neumann entropy (SVNE). It is shown that the indicators that capture the nonlinear correlation between relevant subsystem observables are in excellent agreement with the SVNE.

15 pages, 9 figures

References in corpus (10)

• The physics of exceptional points
• Sudden Death of Entanglement
• Entanglement, avoided crossings and quantum chaos in an Ising model with a tilted magnetic field
• Avoided crossings between bound states of ultracold Cesium dimers
• Generalized entanglement as a framework for complex quantum systems: Purity vs delocalization measures
• Entanglement, Berry Phases, and Level Crossings for the Atomic Breit-Rabi Hamiltonian
• Dispersive Response of a Disordered Superconducting Quantum Metamaterial
• Signatures of nonclassical effects in optical tomograms
• Entanglement dynamics for the double Tavis-Cummings model
• Spectral properties and breathing dynamics of a few-body Bose-Bose mixture in a 1D harmonic trap

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