Erlangen 2018 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 6: Quantum Information (Concepts and Methods) I
Q 6.6: Vortrag
Montag, 5. März 2018, 12:00–12:15, K 1.019
Reconstructing quantum states from single-party information — •Christian Schilling1, Carlos Benavides-Riveros2, and Peter Vrana3 — 1Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom — 2Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle, Germany — 3Department of Geometry, Budapest University of Technology and Economics, Budapest, Hungary
The possible compatibility of density matrices for single-party subsystems is described by linear constraints on their respective spectra. Whenever some of those quantum marginal constraints are saturated, the total quantum state has a specific, simplified structure. We prove that these remarkable global implications of extremal local information are stable, i.e. they hold approximately for spectra close to the boundary of the allowed region. Application of this general result to fermionic quantum systems allows us to characterize natural extensions of the Hartree-Fock ansatz and to quantify their accuracy by resorting to one-particle information, only: The fraction of the correlation energy not recovered by such an ansatz can be estimated from above by a simple geometric quantity in the occupation number picture.