Bonn 2025 – scientific programme
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QI: Fachverband Quanteninformation
QI 35: Quantum Information: Concepts and Methods II
QI 35.9: Talk
Thursday, March 13, 2025, 16:30–16:45, HS IV
Characterising quantum memory via constrained separability problems — •Ties-Albrecht Ohst1, Shijun Zhang3, Hai Chau Nguyen1, Martin Plávala2, and Marco Túlio Quintino3 — 1Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Siegen 57068, Germany — 2Institut für Theoretische Physik, Leibniz Universität Hannover, Hannover, Germany — 3Sorbonne Université, CNRS, LIP6, F-75005 Paris, France
Quantum memories are a crucial precondition in many protocols for processing quantum information. A fundamental problem that illustrates this statement is given by the task of channel discrimination, in which an unknown channel drawn from a known random ensemble should be determined by applying it for a single time. In this talk, we characterise the quality of channel discrimination protocols when the quantum memory, quantified by the auxiliary dimension, is limited. This is achieved by formulating the problem in terms of separable quantum states with additional affine constraints that all of their factors in each separable decomposition obey. We discuss the computation of upper and lower bounds to the solutions of such problems which allow for new insights into the role of memory in channel discrimination. Moreover, the versatility of constrained separability problems in exploring general memory effects, whether classical or quantum, in quantum processes will be showcased.
Keywords: Quantum memory; Channel discrimination; Entanglement; Semidefinite Programming