Wrocław University of Science and Technology Physics Seminar – Monday 15th of December 2025

We cordially invite you to Wrocław University of Science and Technology Physics Seminar on Monday 15th of December 2025 at 11:15 in room 322, building A-1, where there will be delivered a lecture:

Data-driven criteria for quantum correlations

dr hab. Katarzyna Roszak
 
Department of Condensed Matter Theory, Institute of Physics, Czech Academy of Sciences

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We build a machine learning model to detect correlations in a three-qubit system using a neural network trained in an unsupervised manner on randomly generated states. The network is forced to recognize separable states, and correlated states are detected as anomalies. Quite surprisingly, we find that the proposed detector performs much better at distinguishing a weaker form of quantum correlations, namely, the quantum discord, than entanglement. In fact, it has a tendency to grossly overestimate the set of entangled states even at the optimal threshold for entanglement detection, while it underestimates the set of
discordant states to a much lesser extent. In order to illustrate the nature of states classified as quantum-correlated, we construct a diagram containing various types of states — entangled, as well as separable, both discordant and non-discordant. We find that the near-zero value of the recognition loss reproduces the shape of the non-discordant separable states with high accuracy, especially considering the non-trivial shape of this set on the diagram. The network architecture is designed carefully: it preserves separability, and its output is equivariant with respect to qubit permutations. We show that the choice of architecture is important to get the highest detection accuracy, much better than for a baseline model that just utilizes a partial trace operation.