Prepare-and-measure and entanglement simulation beyond qubits

TL;DR

This paper investigates classical simulation of quantum correlations in higher-dimensional systems, extending known protocols from qubits to larger systems and evaluating their robustness through numerical methods.

Contribution

It identifies key features of classical protocols in two dimensions and constructs robust approximate protocols for higher dimensions, advancing understanding of classical simulations.

Findings

Exact simulation for d=2

Robust approximate protocols for higher dimensions

Most robust protocol in studied cases

Abstract

For two non-communicating parties, quantum theory can give rise to probability distributions of outcomes that no local classical model can reproduce without communication. However, in the case of two-dimensional systems ($d=2$), it is known that allowing a finite amount of classical communication to shared classical resources makes it possible to simulate these quantum correlations. Whether such a simulation remains possible in higher dimensions is still an open question. In this work, we identify the key features of the exact classical protocol in $d=2$, and use them to construct robust approximate protocols in higher dimensions. We assess their performance through a randomized numerical study based on the Total Variation Distance. Our approach exactly reproduces the quantum probability distributions for $d=2$, and performs very well compared to existing protocols for higher dimensions, being the most robust protocol in all cases studied. These results offer new insights into the analytical structure of classical protocols in higher dimensions.