Quantum vs. Classical Correlations

Presented at VCQ & quantA Summer School 2026: Reaching Quantum Advantage: Foundations to Applications at the University of Vienna (Vienna, Austria, 2026).

Course dates: 14–15 September 2026.

This lecture will explore the fundamental differences between classical and quantum correlations across a range of operational scenarios. We will begin with the standard Bell nonlocality framework in the nonsignalling setting, highlighting how quantum theory can produce correlations that cannot be reproduced by classical resources, and how this gap enables device-independent certification of entanglement. We will then move to quantum network scenarios, where the constraint of multiple independent sources gives rise to more intricate distinctions between classical and quantum correlations, revealing new forms of nonclassicality. Finally, we consider signaling scenarios that go beyond a fixed causal order and in which noncausal correlations can arise. In this regime, although quantum correlations still exhibit advantages over classical ones, classical resources can already outperform causally ordered models, leading to a different perspective on the classical–quantum boundary.

Course materials

Parts I and II: Nonsignalling and network scenarios

View or download the slides for Parts I and II (PDF)

Part III: Signalling scenarios

View or download the slides for Part III (PDF)

Back to Courses