Structure of Quantum Theory

The prepare-and-measure scenario has been studied continuously in quantum information over a decade. It is the ubiquitous setting for understanding quantum-over-classical advantages in communication. In their simplest setting, in which the receiver has no measurement inputs, quantum communication offers no advantage over classical communication. In constrast, quantum advantage is accessible by combining entanglement with real-time classical feed-forward.
In our work we present a systematic investigation of such quantum advantages in prepare-and-measure scenarios without receiver input, we demonstrate a series of key features. We (i) determine optimal tests of classicality and identify the minimal setting in which quantum advantages come about, (ii) reveal that high-dimensional entanglement plays a key role in quantum advantage, (iii) show that non-projective measurements are indispensable for quantum advantage, which contrasts with most other forms of quantum correlations, and (iv) demonstrate that these scenarios are a natural platform for certifying adaptive one-way LOCC, which is important in quantum networks and error correction.
In summary, our results provide an improved understanding of the prepare-and-measure scenarios without measurement inputs and unveil many of their distinct basic physics features.
Link: https://arxiv.org/abs/2603.29625