Dresden 2026 – wissenschaftliches Programm

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QI: Fachverband Quanteninformation

QI 10: Quantum Information: Concepts and Methods I

QI 10.3: Vortrag

Mittwoch, 11. März 2026, 10:00–10:15, BEY/0137

Identification of unital channels without mixed-unitary representation — •Charlotte Bäcker and Walter Strunz — Dresden University of Technology, Dresden, Germany

Unital quantum channels are characterized by their property of leaving the maximally mixed state invariant. Among these channels are mixed-unitary channels, which can be represented as a probabilistic mixture of unitary operations. For qubits (d = 2), any unital channel is also mixed-unitary, however this does not hold for d > 2. A well-known, open NP-hard problem is to distinguish between these two classes of channels in higher-dimensional quantum dynamics. This question is relevant not only from a theoretical perspective but also for applications in quantum technology (e.g., error correction). In this talk, we will present a new method to identify non-mixed-unitary channels using tools from quantum memory theory. After introducing the relevant concepts, we will demonstrate how this method allows for a more sensitive characterization, illustrated by specific examples.

Keywords: open quantum systems; unital dynamics; mixed-unitary dynamics; quantum memory