Exploring Quantumness at Long-Baseline Neutrino Experiments

TL;DR

This paper develops a comprehensive, data-driven framework to test quantum versus classical behavior in long-baseline neutrino experiments, demonstrating significant violations of classicality with current and upcoming experiments.

Contribution

It introduces a complete statistical approach for Leggett-Garg tests in neutrino experiments, incorporating experimental uncertainties and analyzing multiple experiments for quantum violations.

Findings

T2K shows the most significant violation at ~14 sigma.

NOvA and DUNE also show more than 5 sigma significance.

Framework enables robust differentiation between quantum and classical models.

Abstract

Violations of classicality can be probed through measurements performed on a system at different times, as proposed by Leggett and Garg. Specifically, violations of Leggett-Garg inequalities suggest the presence of quantum effects in macroscopic systems. Long-baseline neutrino experiments provide some of the longest available propagation distances over which such tests can be performed. Previous studies of Leggett-Garg tests in the neutrino sector have largely focused on showing that the oscillation probabilities can violate classical bounds for certain parameter choices. In this work, we develop a more complete and data-driven framework that treats both the distributions representing the classical and quantum behavior, as well as the experimental uncertainties. We consider MINOS, T2K, NOvA, as well as the upcoming DUNE, and present the respective statistical significance for distinguishing quantum behavior from classical scenarios at these long-baseline neutrino experiments. Among them, we find that T2K yields the most significant violation of classicality, at the level of $\sim 14 \sigma$, with NOvA and projections for DUNE also resulting in a significance of more than $5\sigma$.