Spin correlations and entanglement in partially magnetised ensembles of fermions

Abstract

We show that the singlet fraction $p_s$ and total magnetisation (or polarisation) $m$ can bound the minimum concurrence in an ensemble of spins. We identify $p_s>(1-m^2)/2$ as a sufficient and tight condition for bipartite entanglement. Our proof makes no assumptions about the state of the system or symmetry of the particles, and can therefore be used as a witness for spin entanglement between fermions. We discuss the implications for recent experiments in which spin correlations were observed, and the prospect to study entanglement dynamics in the demagnetisation of a cold Fermi gas.

10 pages, 1 figure; submitted to J. Phys. B (for the Special Issue on Addressing Quantum Many-body Problems with Cold Atoms and Molecules)

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Cited by in corpus (2)

• Observation of quantum-limited spin transport in strongly interacting two-dimensional Fermi gases
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